diff --git a/src/compiler/asserts.cpp b/src/compiler/asserts.cpp
index 444422260..5f158474f 100644
--- a/src/compiler/asserts.cpp
+++ b/src/compiler/asserts.cpp
@@ -127,7 +127,7 @@ void replaceAssertVertex(NGHolder &g, NFAVertex t, const ExpressionInfo &expr,
 
     // Wire up all the predecessors to all the successors.
 
-    for (const auto &inEdge : in_edges_range(t, g)) {
+    for (const auto inEdge : in_edges_range(t, g)) {
         NFAVertex u = source(inEdge, g);
         if (u == t) {
             continue; // ignore self-loops
@@ -141,7 +141,7 @@ void replaceAssertVertex(NGHolder &g, NFAVertex t, const ExpressionInfo &expr,
             continue;
         }
 
-        for (const auto &outEdge : out_edges_range(t, g)) {
+        for (const auto outEdge : out_edges_range(t, g)) {
             NFAVertex v = target(outEdge, g);
 
             DEBUG_PRINTF("consider path [%zu,%zu,%zu]\n", g[u].index,
@@ -229,7 +229,7 @@ void checkForMultilineStart(ReportManager &rm, NGHolder &g,
 
         /* we need to interpose a dummy dot vertex between v and accept if
          * required so that ^ doesn't match trailing \n */
-         for (const auto &e : out_edges_range(v, g)) {
+         for (const auto e : out_edges_range(v, g)) {
             if (target(e, g) == g.accept) {
                 dead.push_back(e);
             }
@@ -283,7 +283,7 @@ void removeAssertVertices(ReportManager &rm, NGHolder &g,
 
     // Build a cache of (u, v) vertex pairs to edge descriptors.
     edge_cache_t edge_cache;
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         edge_cache[make_pair(source(e, g), target(e, g))] = e;
     }
 
diff --git a/src/nfa/castlecompile.cpp b/src/nfa/castlecompile.cpp
index 5884ebb21..e1eda5d43 100644
--- a/src/nfa/castlecompile.cpp
+++ b/src/nfa/castlecompile.cpp
@@ -155,7 +155,7 @@ void getNeighborInfo(const CliqueGraph &g, vector<u32> &neighbor,
     u32 id = g[cv].stateId;
 
     // find neighbors for cv
-    for (const auto &v : adjacent_vertices_range(cv, g)) {
+    for (const auto v : adjacent_vertices_range(cv, g)) {
         if (g[v].stateId != id && contains(group, g[v].stateId)) {
             neighbor.push_back(g[v].stateId);
             DEBUG_PRINTF("Neighbor:%u\n", g[v].stateId);
diff --git a/src/nfa/goughcompile.cpp b/src/nfa/goughcompile.cpp
index d41c6f423..3a35984e1 100644
--- a/src/nfa/goughcompile.cpp
+++ b/src/nfa/goughcompile.cpp
@@ -504,7 +504,7 @@ void copy_propagation(GoughGraph &g, const Grey &grey) {
         for (auto v : vertices_range(g)) {
             copy_propagate_update_vars(g[v].vars, &changes);
         }
-        for (const auto &e : edges_range(g)) {
+        for (const auto e : edges_range(g)) {
             copy_propagate_update_vars(g[e].vars, &changes);
         }
     } while(changes);
@@ -562,7 +562,7 @@ void remove_dead(GoughGraph &g) {
             i--;
         }
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         for (u32 i = 0; i < g[e].vars.size(); i++) {
             GoughSSAVar *var = g[e].vars[i].get();
             if (var->seen) {
@@ -896,7 +896,7 @@ static
 void build_blocks(const GoughGraph &g,
                   map<gough_edge_id, vector<gough_ins> > *blocks,
                   u32 base_temp_slot) {
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (g[e].vars.empty()) {
             continue;
         }
@@ -946,7 +946,7 @@ void copy_in_blocks(raw_som_dfa &raw, u8 alphaShift, const GoughGraph &cfg,
     assert(top_sym == raw.alpha_size - 1U);
     map<vector<gough_ins>, u32> &processed = *prog_offsets;
 
-    for (const auto &e : edges_range(cfg)) {
+    for (const auto e : edges_range(cfg)) {
         if (!contains(blocks, gough_edge_id(cfg, e))) {
             continue;
         }
@@ -985,7 +985,7 @@ void copy_in_blocks(raw_som_dfa &raw, u8 alphaShift, const GoughGraph &cfg,
 }
 
 bool find_normal_self_loop(GoughVertex v, const GoughGraph &g, GoughEdge *out) {
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         if (target(e, g) != v) {
             continue;
         }
diff --git a/src/nfa/goughcompile_accel.cpp b/src/nfa/goughcompile_accel.cpp
index 849202a19..080e944a3 100644
--- a/src/nfa/goughcompile_accel.cpp
+++ b/src/nfa/goughcompile_accel.cpp
@@ -146,7 +146,7 @@ bool verify_neighbour(const GoughGraph &g, GoughVertex u,
                       const map<gough_edge_id, vector<gough_ins> > &blocks,
                       const set<GoughVertex> &succs,
                       const vector<gough_ins> &block_sl) {
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         if (!g[e].reach.any()) { /* ignore top edges */
             continue;
         }
@@ -172,7 +172,7 @@ static
 bool verify_neighbour_no_block(const GoughGraph &g, GoughVertex u,
                         const map<gough_edge_id, vector<gough_ins> > &blocks,
                         const set<GoughVertex> &succs) {
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         if (!g[e].reach.any()) { /* ignore top edges */
             continue;
         }
@@ -216,7 +216,7 @@ bool allow_two_byte_accel(const GoughGraph &g,
         const auto &block_sl = blocks.at(gough_edge_id(g, self_loop));
 
         set<GoughVertex> succs;
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             if (g[e].reach.none()) { /* ignore top edges */
                 continue;
             }
@@ -237,7 +237,7 @@ bool allow_two_byte_accel(const GoughGraph &g,
     } else {
         DEBUG_PRINTF("no edge plan on self loop\n");
         set<GoughVertex> succs;
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             if (g[e].reach.none()) { /* ignore top edges */
                 continue;
             }
diff --git a/src/nfa/goughcompile_dump.cpp b/src/nfa/goughcompile_dump.cpp
index 96ab196e3..008d0930f 100644
--- a/src/nfa/goughcompile_dump.cpp
+++ b/src/nfa/goughcompile_dump.cpp
@@ -85,7 +85,7 @@ void dump_graph(const GoughGraph &g, const string &base, const Grey &grey) {
 
         fprintf(f, "label = \"%u\"];\n", g[v].state_id);
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         GoughVertex s = source(e, g);
         GoughVertex t = target(e, g);
 
@@ -153,7 +153,7 @@ void dump_var_mapping(const GoughGraph &g, const string &base,
             fprintf(f, "\n");
         }
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         set<const GoughSSAVar *> used = uses(g[e]);
         if (g[e].vars.empty() && used.empty()) {
             continue;
@@ -200,7 +200,7 @@ void gather_vars(const GoughGraph &g, vector<const GoughSSAVar *> *vars,
         }
     }
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         for (u32 i = 0; i < g[e].vars.size(); i++) {
             const GoughSSAVar *vp = g[e].vars[i].get();
             stringstream ss;
diff --git a/src/nfa/goughcompile_reg.cpp b/src/nfa/goughcompile_reg.cpp
index 48e515b9a..590308924 100644
--- a/src/nfa/goughcompile_reg.cpp
+++ b/src/nfa/goughcompile_reg.cpp
@@ -60,7 +60,7 @@ void all_vars(const GoughGraph &g, vector<GoughSSAVar *> *out) {
     for (auto v : vertices_range(g)) {
         push_back_all_raw(out, g[v].vars);
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         push_back_all_raw(out, g[e].vars);
     }
 }
@@ -89,7 +89,7 @@ void fill_aux(const GoughGraph &g, GoughGraphAux *aux) {
             aux->reporters[var].insert(v);
         }
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         for (const auto &var : g[e].vars) {
             aux->containing_e[var.get()] = e;
             DEBUG_PRINTF("%u is on edge %u->%u\n", var->slot,
@@ -217,7 +217,7 @@ void handle_pending_vertex(GoughVertex def_v, const GoughGraph &g,
         DEBUG_PRINTF("contains target vertex\n");
         return; /* we have reached def */
     }
-    for (const auto &e : in_edges_range(current, g)) {
+    for (const auto e : in_edges_range(current, g)) {
         handle_pending_edge(g, e, nullptr, pending_vertex, rv);
     }
 }
@@ -293,7 +293,7 @@ u32 initial_slots(const GoughGraph &g) {
     for (auto v : vertices_range(g)) {
         set_initial_slots(g[v].vars, &next_slot);
     }
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         set_initial_slots(g[e].vars, &next_slot);
     }
 
@@ -405,7 +405,7 @@ void find_dom_ordering(const GoughGraph &cfg, vector<GoughSSAVar *> *out) {
 
     for (auto it = g_order.rbegin(); it != g_order.rend(); ++it) {
         add_to_dom_ordering(cfg[*it].vars, out);
-        for (const auto &e : out_edges_range(*it, cfg)) {
+        for (const auto e : out_edges_range(*it, cfg)) {
             add_to_dom_ordering(cfg[e].vars, out);
         }
     }
@@ -444,7 +444,7 @@ void update_local_slots(GoughGraph &g, set<GoughSSAVar *> &locals,
     /* local variables only occur on edges (joins are never local) */
 
     u32 allocated_count = 0;
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         u32 next_slot = local_base;
         for (auto &var : g[e].vars) {
             if (contains(locals, var.get())) {
diff --git a/src/nfa/limex_compile.cpp b/src/nfa/limex_compile.cpp
index 9233ae515..1c9a4a865 100644
--- a/src/nfa/limex_compile.cpp
+++ b/src/nfa/limex_compile.cpp
@@ -1239,7 +1239,7 @@ void findMaskedCompressionStates(const build_info &args,
     if (!inspects_states_for_accepts(h)
         && !hasInitDsStates(h, args.state_ids)) {
         NFAStateSet nonleaf(args.num_states);
-        for (const auto &e : edges_range(h)) {
+        for (const auto e : edges_range(h)) {
             u32 from = args.state_ids.at(source(e, h));
             u32 to = args.state_ids.at(target(e, h));
             if (from == NO_STATE) {
@@ -1459,7 +1459,7 @@ u32 buildExceptionMap(const build_info &args, ReportListCache &reports_cache,
         }
 
         // are we a non-limited transition?
-        for (const auto &oe : out_edges_range(v, h)) {
+        for (const auto oe : out_edges_range(v, h)) {
             if (contains(exceptional, oe)) {
                 NFAVertex w = target(oe, h);
                 u32 w_idx = args.state_ids.at(w);
@@ -1550,7 +1550,7 @@ static
 u32 findMaxVarShift(const build_info &args, u32 nShifts) {
     const NGHolder &h = args.h;
     u32 shiftMask = 0;
-    for (const auto &e : edges_range(h)) {
+    for (const auto e : edges_range(h)) {
         u32 from = args.state_ids.at(source(e, h));
         u32 to = args.state_ids.at(target(e, h));
         if (from == NO_STATE || to == NO_STATE) {
@@ -1579,7 +1579,7 @@ int getLimexScore(const build_info &args, u32 nShifts) {
     maxVarShift = findMaxVarShift(args, nShifts);
 
     NFAStateSet exceptionalStates(args.num_states);
-    for (const auto &e : edges_range(h)) {
+    for (const auto e : edges_range(h)) {
         u32 from = args.state_ids.at(source(e, h));
         u32 to = args.state_ids.at(target(e, h));
         if (from == NO_STATE || to == NO_STATE) {
@@ -1870,7 +1870,7 @@ struct Factory {
         u32 shiftMask = 0;
         int shiftMaskIdx = 0;
 
-        for (const auto &e : edges_range(h)) {
+        for (const auto e : edges_range(h)) {
             u32 from = args.state_ids.at(source(e, h));
             u32 to = args.state_ids.at(target(e, h));
             if (from == NO_STATE || to == NO_STATE) {
@@ -1908,7 +1908,7 @@ struct Factory {
                                     u32 maxShift) {
         const NGHolder &h = args.h;
 
-        for (const auto &e : edges_range(h)) {
+        for (const auto e : edges_range(h)) {
             u32 from = args.state_ids.at(source(e, h));
             u32 to = args.state_ids.at(target(e, h));
             if (from == NO_STATE || to == NO_STATE) {
diff --git a/src/nfa/mcsheng_compile.cpp b/src/nfa/mcsheng_compile.cpp
index fb75e49a3..0a0af0406 100644
--- a/src/nfa/mcsheng_compile.cpp
+++ b/src/nfa/mcsheng_compile.cpp
@@ -549,7 +549,7 @@ dstate_id_t find_sheng_states(dfa_info &info,
         /* get an estimate of stickness of the cyclic: assume any edges from
          * states with larger state ids are back edges */
         CharReach est_back_reach;
-        for (const auto &u : inv_adjacent_vertices_range(v, g)) {
+        for (const auto u : inv_adjacent_vertices_range(v, g)) {
             if (g[u].index < g[v].index) {
                 continue;
             }
@@ -587,7 +587,7 @@ dstate_id_t find_sheng_states(dfa_info &info,
         }
 
         sheng_states.insert(v);
-        for (const auto &t : adjacent_vertices_range(v, g)) {
+        for (const auto t : adjacent_vertices_range(v, g)) {
             if (!contains(considered, g[t].index)) {
                 to_consider.push_back(t);
             }
diff --git a/src/nfagraph/ng_anchored_dots.cpp b/src/nfagraph/ng_anchored_dots.cpp
index 9a13376d1..0c50848cf 100644
--- a/src/nfagraph/ng_anchored_dots.cpp
+++ b/src/nfagraph/ng_anchored_dots.cpp
@@ -177,7 +177,7 @@ void reformAnchoredRepeatsComponent(NGHolder &g,
     bool selfLoop = false;
     bool bustOut = false;
 
-    for (const auto &e : out_edges_range(dotV, g)) {
+    for (const auto e : out_edges_range(dotV, g)) {
         NFAVertex t = target(e, g);
         if (t == dotV) {
             selfLoop = true;
@@ -280,7 +280,7 @@ void reformUnanchoredRepeatsComponent(NGHolder &g,
         bool selfLoop = false;
         bool bustOut = false;
 
-        for (const auto &e : out_edges_range(dotV, g)) {
+        for (const auto e : out_edges_range(dotV, g)) {
             NFAVertex t = target(e, g);
 
             if (t == dotV) {
diff --git a/src/nfagraph/ng_asserts.cpp b/src/nfagraph/ng_asserts.cpp
index 8812afadb..fd74a2aa4 100644
--- a/src/nfagraph/ng_asserts.cpp
+++ b/src/nfagraph/ng_asserts.cpp
@@ -92,7 +92,7 @@ static const CharReach CHARREACH_NONWORD_UCP_PRE(CHARREACH_NONWORD);
 static
 vector<NFAEdge> getAsserts(const NGHolder &g) {
     vector<NFAEdge> out;
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (g[e].assert_flags) {
             out.push_back(e);
         }
@@ -255,7 +255,7 @@ void splitVertex(ReportManager &rm, NGHolder &g, const ExpressionInfo &expr,
 static
 void resolveEdges(ReportManager &rm, NGHolder &g, const ExpressionInfo &expr,
                   set<NFAEdge> *dead) {
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         u32 flags = g[e].assert_flags;
         if (!flags) {
             continue;
diff --git a/src/nfagraph/ng_calc_components.cpp b/src/nfagraph/ng_calc_components.cpp
index 3e9454eee..0ff6748c1 100644
--- a/src/nfagraph/ng_calc_components.cpp
+++ b/src/nfagraph/ng_calc_components.cpp
@@ -198,7 +198,7 @@ vector<NFAEdge> findShellEdges(const NGHolder &g,
                                const flat_set<NFAVertex> &tail_shell) {
     vector<NFAEdge> shell_edges;
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         auto u = source(e, g);
         auto v = target(e, g);
 
diff --git a/src/nfagraph/ng_cyclic_redundancy.cpp b/src/nfagraph/ng_cyclic_redundancy.cpp
index 0b24bf07a..134856c60 100644
--- a/src/nfagraph/ng_cyclic_redundancy.cpp
+++ b/src/nfagraph/ng_cyclic_redundancy.cpp
@@ -173,7 +173,7 @@ bool removeCyclicPathRedundancy(Graph &g, typename Graph::vertex_descriptor v,
 
     flat_set<vertex_descriptor> s;
 
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         vertex_descriptor u = source(e, g);
         if (u == v) {
             continue;
diff --git a/src/nfagraph/ng_depth.cpp b/src/nfagraph/ng_depth.cpp
index 6c90326ce..d42013344 100644
--- a/src/nfagraph/ng_depth.cpp
+++ b/src/nfagraph/ng_depth.cpp
@@ -156,7 +156,7 @@ vector<bool> findLoopReachable(const Graph &g,
     }
 
     for (auto v : reverse(topoOrder)) {
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             if (deadNodes[g[source(e, g)].index]) {
                 deadNodes[g[v].index] = true;
                 break;
diff --git a/src/nfagraph/ng_edge_redundancy.cpp b/src/nfagraph/ng_edge_redundancy.cpp
index b8354bd42..e3a75cdb5 100644
--- a/src/nfagraph/ng_edge_redundancy.cpp
+++ b/src/nfagraph/ng_edge_redundancy.cpp
@@ -351,7 +351,7 @@ void checkLargeOutU(const NGHolder &g, NFAVertex u,
         return;
     }
 
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         const NFAVertex v = target(e, g);
 
         if (is_special(v, g)) {
@@ -364,7 +364,7 @@ void checkLargeOutU(const NGHolder &g, NFAVertex u,
 
         /* Now need check to find any edges which can be removed due to the
          * existence of edge e */
-        for (const auto &e2 : in_edges_range(v, g)) {
+        for (const auto e2 : in_edges_range(v, g)) {
             if (e == e2 || contains(*dead, e2)) {
                 continue;
             }
@@ -386,7 +386,7 @@ void checkSmallOutU(const NGHolder &g, NFAVertex u,
                     const flat_set<NFAVertex> &parents_u,
                     map<NFAVertex, bool> &done,
                     set<NFAEdge> *dead) {
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         const NFAVertex v = target(e, g);
 
         if (is_special(v, g)) {
@@ -399,7 +399,7 @@ void checkSmallOutU(const NGHolder &g, NFAVertex u,
 
         /* Now need check to find any edges which can be removed due to the
          * existence of edge e */
-        for (const auto &e2 : in_edges_range(v, g)) {
+        for (const auto e2 : in_edges_range(v, g)) {
             if (e == e2 || contains(*dead, e2)) {
                 continue;
             }
@@ -487,7 +487,7 @@ bool removeSiblingsOfStartDotStar(NGHolder &g) {
             continue;
         }
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             NFAVertex u = source(e, g);
             if (is_special(u, g)) {
                 continue;
@@ -518,7 +518,7 @@ bool optimiseVirtualStarts(NGHolder &g) {
             continue;
         }
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             if (!is_any_start(source(e, g), g)) {
                 dead.push_back(e);
             }
diff --git a/src/nfagraph/ng_equivalence.cpp b/src/nfagraph/ng_equivalence.cpp
index a42a0ac71..616bfddd7 100644
--- a/src/nfagraph/ng_equivalence.cpp
+++ b/src/nfagraph/ng_equivalence.cpp
@@ -243,12 +243,12 @@ bool isIrreducible(const NGHolder &g) {
 #ifndef NDEBUG
 static
 bool hasEdgeAsserts(NFAVertex v, const NGHolder &g) {
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         if (g[e].assert_flags != 0) {
             return true;
         }
     }
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         if (g[e].assert_flags != 0) {
             return true;
         }
@@ -280,7 +280,7 @@ vector<unique_ptr<VertexInfo>> getVertexInfos(const NGHolder &g) {
         NFAVertex v = vi->v;
 
         // find predecessors
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             NFAVertex u = source(e, g);
             VertexInfo *u_vi = vertex_map[g[u].index];
 
diff --git a/src/nfagraph/ng_execute.cpp b/src/nfagraph/ng_execute.cpp
index 9d9048947..ee7f1a9ce 100644
--- a/src/nfagraph/ng_execute.cpp
+++ b/src/nfagraph/ng_execute.cpp
@@ -97,7 +97,7 @@ void filter_by_reach(const vector<StateInfo> &info, dynamic_bitset<> *states,
     }
 }
 
-template<typename inputT>
+template<typename inputT, typename elementT>
 static
 void execute_graph_i(const NGHolder &g, const vector<StateInfo> &info,
                      const inputT &input, dynamic_bitset<> *states,
@@ -106,7 +106,7 @@ void execute_graph_i(const NGHolder &g, const vector<StateInfo> &info,
     dynamic_bitset<> next(curr.size());
     DEBUG_PRINTF("%zu states in\n", states->count());
 
-    for (const auto &e : input) {
+    for (elementT e : input) {
         DEBUG_PRINTF("processing %s\n", describeClass(e).c_str());
         step(g, info, curr, &next);
         if (kill_sds) {
@@ -165,7 +165,7 @@ flat_set<NFAVertex> execute_graph(const NGHolder &g, const ue2_literal &input,
     auto info = makeInfoTable(g);
     auto work_states = makeStateBitset(g, initial_states);
 
-    execute_graph_i(g, info, input, &work_states, kill_sds);
+    execute_graph_i<ue2_literal, const ue2_literal::elem>(g, info, input, &work_states, kill_sds);
 
     return getVertices(work_states, info);
 }
@@ -178,7 +178,7 @@ flat_set<NFAVertex> execute_graph(const NGHolder &g,
     auto info = makeInfoTable(g);
     auto work_states = makeStateBitset(g, initial_states);
 
-    execute_graph_i(g, info, input, &work_states, false);
+    execute_graph_i<vector<CharReach>, const CharReach&>(g, info, input, &work_states, false);
 
     return getVertices(work_states, info);
 }
diff --git a/src/nfagraph/ng_extparam.cpp b/src/nfagraph/ng_extparam.cpp
index 6eb23113f..bb632003b 100644
--- a/src/nfagraph/ng_extparam.cpp
+++ b/src/nfagraph/ng_extparam.cpp
@@ -409,7 +409,7 @@ bool anchorPatternWithBoundedRepeat(NGHolder &g, ReportManager &rm) {
 static
 NFAVertex findSingleCyclic(const NGHolder &g) {
     NFAVertex v = NGHolder::null_vertex();
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (source(e, g) == target(e, g)) {
             if (source(e, g) == g.startDs) {
                 continue;
@@ -580,7 +580,7 @@ bool transformMinLengthToRepeat(NGHolder &g, ReportManager &rm) {
 
         // We want to delete the out-edges of each predecessor, but need to
         // make sure we don't delete the startDs self loop.
-        for (const auto &e : out_edges_range(u, g)) {
+        for (const auto e : out_edges_range(u, g)) {
             if (target(e, g) != g.startDs) {
                 dead.push_back(e);
             }
@@ -729,7 +729,7 @@ void pruneExtUnreachable(NGHolder &g, const ReportManager &rm) {
 
     vector<NFAEdge> dead;
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (isEdgePrunable(g, report, depths, e)) {
             DEBUG_PRINTF("pruning\n");
             dead.push_back(e);
@@ -767,7 +767,7 @@ void pruneVacuousEdges(NGHolder &g, const ReportManager &rm) {
         });
     };
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         const NFAVertex u = source(e, g);
         const NFAVertex v = target(e, g);
 
@@ -802,7 +802,7 @@ void pruneUnmatchable(NGHolder &g, const vector<DepthMinMax> &depths,
                       const ReportManager &rm, NFAVertex accept) {
     vector<NFAEdge> dead;
 
-    for (const auto &e : in_edges_range(accept, g)) {
+    for (const auto e : in_edges_range(accept, g)) {
         NFAVertex v = source(e, g);
         if (v == g.accept) {
             assert(accept == g.acceptEod); // stylised edge
diff --git a/src/nfagraph/ng_is_equal.cpp b/src/nfagraph/ng_is_equal.cpp
index 35a09d0ea..11da42eaa 100644
--- a/src/nfagraph/ng_is_equal.cpp
+++ b/src/nfagraph/ng_is_equal.cpp
@@ -172,10 +172,10 @@ bool is_equal_i(const NGHolder &a, const NGHolder &b,
     vector<pair<u32, flat_set<u32>>> top_a;
     vector<pair<u32, flat_set<u32>>> top_b;
 
-    for (const auto &e : out_edges_range(a.start, a)) {
+    for (const auto e : out_edges_range(a.start, a)) {
         top_a.emplace_back(a[target(e, a)].index, a[e].tops);
     }
-    for (const auto &e : out_edges_range(b.start, b)) {
+    for (const auto e : out_edges_range(b.start, b)) {
         top_b.emplace_back(b[target(e, b)].index, b[e].tops);
     }
 
diff --git a/src/nfagraph/ng_limex.cpp b/src/nfagraph/ng_limex.cpp
index 2f0a55eab..721238afe 100644
--- a/src/nfagraph/ng_limex.cpp
+++ b/src/nfagraph/ng_limex.cpp
@@ -424,7 +424,7 @@ void makeTopStates(NGHolder &g, map<u32, set<NFAVertex>> &tops_out,
 
     map<u32, flat_set<NFAVertex>> top_succs;
     map<NFAVertex, flat_set<u32>> succ_tops;
-    for (const auto &e : out_edges_range(g.start, g)) {
+    for (const auto e : out_edges_range(g.start, g)) {
         NFAVertex v = target(e, g);
         for (u32 t : g[e].tops) {
             top_succs[t].insert(v);
@@ -510,7 +510,7 @@ set<NFAVertex> findZombies(const NGHolder &h,
     ok:;
     }
 
-    for (const auto &v : inv_adjacent_vertices_range(h.accept, h)) {
+    for (const auto v : inv_adjacent_vertices_range(h.accept, h)) {
         if (state_ids.at(v) != NO_STATE) {
             zombies.insert(v);
         }
@@ -610,7 +610,7 @@ prepareGraph(const NGHolder &h_in, const ReportManager *rm,
 
 static
 void remapReportsToPrograms(NGHolder &h, const ReportManager &rm) {
-    for (const auto &v : vertices_range(h)) {
+    for (const auto v : vertices_range(h)) {
         auto &reports = h[v].reports;
         if (reports.empty()) {
             continue;
diff --git a/src/nfagraph/ng_literal_analysis.cpp b/src/nfagraph/ng_literal_analysis.cpp
index d25ac43e8..594d6cba0 100644
--- a/src/nfagraph/ng_literal_analysis.cpp
+++ b/src/nfagraph/ng_literal_analysis.cpp
@@ -119,7 +119,7 @@ void dumpGraph(const char *filename, const LitGraph &lg) {
         fout << endl;
     }
 
-    for (const auto &e : edges_range(lg)) {
+    for (const auto e : edges_range(lg)) {
         LitVertex u = source(e, lg), v = target(e, lg);
         fout << lg[u].index << " -> " << lg[v].index << "[label=\""
              << lg[e].score << "\"]"
@@ -359,7 +359,7 @@ u64a litUniqueness(const string &s) {
 static
 u64a litCountBits(const ue2_literal &lit) {
     u64a n = 0;
-    for (const auto &c : lit) {
+    for (const auto c : lit) {
         n += c.nocase ? 7 : 8;
     }
     return n;
@@ -488,7 +488,7 @@ vector<LitEdge> add_reverse_edges_and_index(LitGraph &lg) {
     const size_t edge_count = num_edges(lg);
     vector<LitEdge> fwd_edges;
     fwd_edges.reserve(edge_count);
-    for (const auto &e : edges_range(lg)) {
+    for (const auto e : edges_range(lg)) {
         fwd_edges.push_back(e);
     }
 
@@ -547,7 +547,7 @@ void findMinCut(LitGraph &lg, vector<LitEdge> &cutset) {
     vector<LitEdge> white_cut, black_cut;
     u64a white_flow = 0, black_flow = 0;
 
-    for (const auto &e : edges_range(lg)) {
+    for (const auto e : edges_range(lg)) {
         const LitVertex u = source(e, lg), v = target(e, lg);
         const auto ucolor = get(colors, u);
         const auto vcolor = get(colors, v);
@@ -694,7 +694,7 @@ set<ue2_literal> getLiteralSet(const NGHolder &g, const NFAVertex &v,
 
     set<ue2_literal> ls;
 
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         if (source(e, g) == v && only_first_encounter) {
             continue; /* ignore self loop on root vertex as we are interested in
                        * the first time we visit the vertex on the way to
@@ -719,7 +719,7 @@ vector<u64a> scoreEdges(const NGHolder &g, const flat_set<NFAEdge> &known_bad) {
 
     vector<u64a> scores(num_edges(g));
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         u32 eidx = g[e].index;
         assert(eidx < scores.size());
         if (contains(known_bad, e)) {
diff --git a/src/nfagraph/ng_literal_decorated.cpp b/src/nfagraph/ng_literal_decorated.cpp
index 61a31dbf3..ba1b6f9f5 100644
--- a/src/nfagraph/ng_literal_decorated.cpp
+++ b/src/nfagraph/ng_literal_decorated.cpp
@@ -132,7 +132,7 @@ bool findPaths(const NGHolder &g, vector<Path> &paths) {
 
 static
 bool hasLargeDegreeVertex(const NGHolder &g) {
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (is_special(v, g)) { // specials can have large degree
             continue;
         }
diff --git a/src/nfagraph/ng_mcclellan_internal.h b/src/nfagraph/ng_mcclellan_internal.h
index f069d7336..a73568df8 100644
--- a/src/nfagraph/ng_mcclellan_internal.h
+++ b/src/nfagraph/ng_mcclellan_internal.h
@@ -98,7 +98,7 @@ void transition_graph(autom &nfa, const std::vector<NFAVertex> &vByStateId,
     for (size_t i = in.find_first(); i != in.npos; i = in.find_next(i)) {
         NFAVertex u = vByStateId[i];
 
-        for (const auto &v : adjacent_vertices_range(u, graph)) {
+        for (const auto v : adjacent_vertices_range(u, graph)) {
             if (contains(unused, v)) {
                 continue;
             }
diff --git a/src/nfagraph/ng_misc_opt.cpp b/src/nfagraph/ng_misc_opt.cpp
index 8aaaf99fd..e5849dcce 100644
--- a/src/nfagraph/ng_misc_opt.cpp
+++ b/src/nfagraph/ng_misc_opt.cpp
@@ -511,7 +511,7 @@ bool mergeCyclicDotStars(NGHolder &g) {
             vector<NFAEdge> deadEdges;
 
             // check if all adjacent vertices have edges from start
-            for (const auto &e : out_edges_range(v, g)) {
+            for (const auto e : out_edges_range(v, g)) {
                 NFAVertex t = target(e, g);
                 // skip self
                 if (t == v) {
diff --git a/src/nfagraph/ng_netflow.cpp b/src/nfagraph/ng_netflow.cpp
index 780a319f5..066b2ed76 100644
--- a/src/nfagraph/ng_netflow.cpp
+++ b/src/nfagraph/ng_netflow.cpp
@@ -77,7 +77,7 @@ void addReverseEdges(NGHolder &g, vector<NFAEdge> &reverseEdge,
     // To avoid walking the graph for _ages_, we build a temporary map of all
     // edges indexed by vertex pair for existence checks.
     map<pair<size_t, size_t>, NFAEdge> allEdges;
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         NFAVertex u = source(e, g), v = target(e, g);
         size_t uidx = g[u].index, vidx = g[v].index;
         allEdges[make_pair(uidx, vidx)] = e;
@@ -177,7 +177,7 @@ vector<NFAEdge> findMinCut(NGHolder &h, const vector<u64a> &scores) {
     u64a observed_black_flow = 0;
     u64a observed_white_flow = 0;
 
-    for (const auto &e : edges_range(h)) {
+    for (const auto e : edges_range(h)) {
         NFAVertex from = source(e, h);
         NFAVertex to = target(e, h);
         u64a ec = scores[h[e].index];
diff --git a/src/nfagraph/ng_prefilter.cpp b/src/nfagraph/ng_prefilter.cpp
index 04611872a..b2e79edb6 100644
--- a/src/nfagraph/ng_prefilter.cpp
+++ b/src/nfagraph/ng_prefilter.cpp
@@ -215,7 +215,7 @@ map<u32, RegionInfo> findRegionInfo(const NGHolder &h,
 
 static
 void copyInEdges(NGHolder &g, NFAVertex from, NFAVertex to) {
-    for (const auto &e : in_edges_range(from, g)) {
+    for (const auto e : in_edges_range(from, g)) {
         NFAVertex u = source(e, g);
         add_edge_if_not_present(u, to, g[e], g);
     }
@@ -223,7 +223,7 @@ void copyInEdges(NGHolder &g, NFAVertex from, NFAVertex to) {
 
 static
 void copyOutEdges(NGHolder &g, NFAVertex from, NFAVertex to) {
-    for (const auto &e : out_edges_range(from, g)) {
+    for (const auto e : out_edges_range(from, g)) {
         NFAVertex t = target(e, g);
         add_edge_if_not_present(to, t, g[e], g);
 
diff --git a/src/nfagraph/ng_prune.cpp b/src/nfagraph/ng_prune.cpp
index adda70312..f5972d26d 100644
--- a/src/nfagraph/ng_prune.cpp
+++ b/src/nfagraph/ng_prune.cpp
@@ -205,7 +205,7 @@ void pruneHighlanderAccepts(NGHolder &g, const ReportManager &rm) {
         }
 
         // We can prune any out-edges that aren't accepts
-        for (const auto &e : out_edges_range(u, g)) {
+        for (const auto e : out_edges_range(u, g)) {
             if (!is_any_accept(target(e, g), g)) {
                 dead.push_back(e);
             }
@@ -304,7 +304,7 @@ void pruneHighlanderDominated(NGHolder &g, const ReportManager &rm) {
     // If a reporter vertex is dominated by another with the same report, we
     // can remove that report; if all reports are removed, we can remove the
     // vertex entirely.
-    for (const auto v : reporters) {
+    for (const auto &v : reporters) {
         const auto reports = g[v].reports; // copy, as we're going to mutate
         for (const auto &report_id : reports) {
             if (!isSimpleExhaustible(rm.getReport(report_id))) {
@@ -329,7 +329,7 @@ void pruneHighlanderDominated(NGHolder &g, const ReportManager &rm) {
     // If a reporter vertex has a self-loop, but otherwise only leads to accept
     // (note: NOT acceptEod) and has simple exhaustible reports, we can delete
     // the self-loop.
-    for (const auto v : reporters) {
+    for (const auto &v : reporters) {
         if (hasOnlySelfLoopAndExhaustibleAccepts(g, rm, v)) {
             remove_edge(v, v, g);
             modified = true;
@@ -353,7 +353,7 @@ void pruneHighlanderDominated(NGHolder &g, const ReportManager &rm) {
 void pruneReport(NGHolder &g, ReportID report) {
     set<NFAEdge> dead;
 
-    for (const auto &e : in_edges_range(g.accept, g)) {
+    for (const auto e : in_edges_range(g.accept, g)) {
         NFAVertex u = source(e, g);
         auto &reports = g[u].reports;
         if (contains(reports, report)) {
@@ -364,7 +364,7 @@ void pruneReport(NGHolder &g, ReportID report) {
         }
     }
 
-    for (const auto &e : in_edges_range(g.acceptEod, g)) {
+    for (const auto e : in_edges_range(g.acceptEod, g)) {
         NFAVertex u = source(e, g);
         if (u == g.accept) {
             continue;
@@ -394,7 +394,7 @@ void pruneReport(NGHolder &g, ReportID report) {
 void pruneAllOtherReports(NGHolder &g, ReportID report) {
     set<NFAEdge> dead;
 
-    for (const auto &e : in_edges_range(g.accept, g)) {
+    for (const auto e : in_edges_range(g.accept, g)) {
         NFAVertex u = source(e, g);
         auto &reports = g[u].reports;
         if (contains(reports, report)) {
@@ -406,7 +406,7 @@ void pruneAllOtherReports(NGHolder &g, ReportID report) {
         }
     }
 
-    for (const auto &e : in_edges_range(g.acceptEod, g)) {
+    for (const auto e : in_edges_range(g.acceptEod, g)) {
         NFAVertex u = source(e, g);
         if (u == g.accept) {
             continue;
diff --git a/src/nfagraph/ng_redundancy.cpp b/src/nfagraph/ng_redundancy.cpp
index 06b9daeec..7adfe2eef 100644
--- a/src/nfagraph/ng_redundancy.cpp
+++ b/src/nfagraph/ng_redundancy.cpp
@@ -768,7 +768,7 @@ void findCyclicDom(NGHolder &g, vector<bool> &cyclic,
 
             // iff all paths through in-edge e of v involve vertices whose
             // reachability is a subset of reach(dom), we can delete edge e.
-            for (const auto &e : in_edges_range(v, g)) {
+            for (const auto e : in_edges_range(v, g)) {
                 if (source(e, g) == dom) {
                     continue;
                 }
@@ -806,7 +806,7 @@ void findCyclicPostDom(NGHolder &g, vector<bool> &cyclic,
 
             // iff all paths through in-edge e of v involve vertices whose
             // reachability is a subset of reach(dom), we can delete edge e.
-            for (const auto &e : out_edges_range(v, g)) {
+            for (const auto e : out_edges_range(v, g)) {
                 if (target(e, g) == postdom) {
                     continue;
                 }
diff --git a/src/nfagraph/ng_region.cpp b/src/nfagraph/ng_region.cpp
index 2675be643..dd033def5 100644
--- a/src/nfagraph/ng_region.cpp
+++ b/src/nfagraph/ng_region.cpp
@@ -389,7 +389,7 @@ void liftSinks(const AcyclicGraph &acyclic_g, vector<NFAVertex> &topoOrder) {
         NFAVertex s = *ri;
         DEBUG_PRINTF("handling sink %zu\n", acyclic_g[s].index);
         unordered_set<NFAVertex> parents;
-        for (const auto &e : in_edges_range(s, acyclic_g)) {
+        for (const auto e : in_edges_range(s, acyclic_g)) {
             parents.insert(NFAVertex(source(e, acyclic_g)));
         }
 
diff --git a/src/nfagraph/ng_region.h b/src/nfagraph/ng_region.h
index a4708a582..fd5f88358 100644
--- a/src/nfagraph/ng_region.h
+++ b/src/nfagraph/ng_region.h
@@ -115,7 +115,7 @@ bool isRegionEntry(const Graph &g, NFAVertex v,
                    const std::unordered_map<NFAVertex, u32> &region_map) {
     // Note that some graph types do not have inv_adjacent_vertices, so we must
     // use in_edges here.
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         if (!inSameRegion(g, v, source(e, g), region_map)) {
             return true;
         }
@@ -141,7 +141,7 @@ bool isRegionExit(const Graph &g, NFAVertex v,
 template <class Graph>
 bool isSingletonRegion(const Graph &g, NFAVertex v,
                        const std::unordered_map<NFAVertex, u32> &region_map) {
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         auto u = source(e, g);
         if (u != v && inSameRegion(g, v, u, region_map)) {
             return false;
@@ -159,7 +159,7 @@ bool isSingletonRegion(const Graph &g, NFAVertex v,
             return false;
         }
 
-        for (const auto &e : in_edges_range(w, g)) {
+        for (const auto e : in_edges_range(w, g)) {
             auto u = source(e, g);
             if (u != v && inSameRegion(g, v, u, region_map)) {
                 return false;
@@ -193,7 +193,7 @@ bool isOptionalRegion(const Graph &g, NFAVertex v,
     // Optional if v has a predecessor in an earlier region that has a
     // successor in a later one.
 
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         auto u = source(e, g);
         if (inSameRegion(g, v, u, region_map)) {
             continue;
diff --git a/src/nfagraph/ng_repeat.cpp b/src/nfagraph/ng_repeat.cpp
index 1f63ad3c6..735466d37 100644
--- a/src/nfagraph/ng_repeat.cpp
+++ b/src/nfagraph/ng_repeat.cpp
@@ -230,7 +230,7 @@ bool hasDifferentTops(const NGHolder &g, const vector<NFAVertex> &verts) {
     const flat_set<u32> *tops = nullptr;
 
     for (auto v : verts) {
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             NFAVertex u = source(e, g);
             if (u != g.start && u != g.startDs) {
                 continue; // Only edges from starts have valid top properties.
@@ -732,7 +732,7 @@ void unpeelNearEnd(NGHolder &g, ReachSubgraph &rsi,
         } else {
             /* Skip edge for the cyclic state; note that we must clone their
              * edge properties as they may include tops. */
-            for (const auto &e : in_edges_range(first, g)) {
+            for (const auto e : in_edges_range(first, g)) {
                 add_edge(source(e, g), d, g[e], g);
             }
         }
@@ -813,7 +813,7 @@ void replaceSubgraphWithSpecial(NGHolder &g, ReachSubgraph &rsi,
         depths[first].fromStartDotStar, depths[last].fromStartDotStar);
 
     // Wire predecessors to positive trigger.
-    for (const auto &e : in_edges_range(first, g)) {
+    for (const auto e : in_edges_range(first, g)) {
         add_edge(source(e, g), pos_trigger, g[e], g);
     }
 
@@ -880,7 +880,7 @@ void replaceSubgraphWithLazySpecial(NGHolder &g, ReachSubgraph &rsi,
         depths[first].fromStartDotStar, depths[last].fromStartDotStar);
 
     // Wire predecessors to positive trigger.
-    for (const auto &e : in_edges_range(first, g)) {
+    for (const auto e : in_edges_range(first, g)) {
         add_edge(source(e, g), pos_trigger, g[e], g);
     }
 
@@ -1159,7 +1159,7 @@ void addTriggers(NGHolder &g,
     vector<NFAEdge> dead;
     map<u32, vector<NFAVertex>> starts_by_top;
 
-    for (const auto &e : out_edges_range(g.start, g)) {
+    for (const auto e : out_edges_range(g.start, g)) {
         const NFAVertex &v = target(e, g);
         if (v == g.startDs) {
             continue;
@@ -1402,7 +1402,7 @@ bool hasSoleEntry(const NGHolder &g, const ReachSubgraph &rsi,
         region_map.emplace(rg_map.at(v), repeat_region);
     }
 
-    for (const auto &v : vertices_range(rg)) {
+    for (const auto v : vertices_range(rg)) {
         if (!contains(region_map, v)) {
             DEBUG_PRINTF("rg vertex %zu in lhs (trigger)\n", rg[v].index);
             region_map.emplace(v, lhs_region);
@@ -2110,7 +2110,7 @@ void populateFixedTopInfo(const map<u32, u32> &fixed_depth_tops,
     unordered_map<NFAVertex, depth> top_depths;
     auto colours = make_small_color_map(g);
 
-    for (const auto &e : out_edges_range(g.start, g)) {
+    for (const auto e : out_edges_range(g.start, g)) {
         NFAVertex v = target(e, g);
         if (v == g.startDs) {
             continue;
@@ -2409,7 +2409,7 @@ void analyseRepeats(NGHolder &g, const ReportManager *rm,
 static
 bool allOneReach(const NGHolder &g) {
     const CharReach *cr = nullptr;
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (is_special(v, g)) {
             continue;
         }
diff --git a/src/nfagraph/ng_restructuring.cpp b/src/nfagraph/ng_restructuring.cpp
index 704697e57..6cda479e5 100644
--- a/src/nfagraph/ng_restructuring.cpp
+++ b/src/nfagraph/ng_restructuring.cpp
@@ -134,7 +134,7 @@ static
 unordered_map<NFAVertex, u32>
 getStateIndices(const NGHolder &h, const vector<NFAVertex> &ordering) {
     unordered_map<NFAVertex, u32> states;
-    for (const auto &v : vertices_range(h)) {
+    for (const auto v : vertices_range(h)) {
         states[v] = NO_STATE;
     }
 
diff --git a/src/nfagraph/ng_som.cpp b/src/nfagraph/ng_som.cpp
index d23ac408b..197b03640 100644
--- a/src/nfagraph/ng_som.cpp
+++ b/src/nfagraph/ng_som.cpp
@@ -1131,7 +1131,7 @@ void expandGraph(NGHolder &g, unordered_map<NFAVertex, u32> &regions,
         for (const auto &m : orig_to_copy) {
             NFAVertex v = m.first, v2 = m.second;
 
-            for (const auto &e : out_edges_range(v, g)) {
+            for (const auto e : out_edges_range(v, g)) {
                 NFAVertex t = target(e, g);
                 u32 t_region = regions.at(t);
                 if (t_region >= split_region && !is_special(t, g)) {
@@ -1141,7 +1141,7 @@ void expandGraph(NGHolder &g, unordered_map<NFAVertex, u32> &regions,
                 add_edge_if_not_present(v2, t, g[e], g);
             }
 
-            for (const auto &e : in_edges_range(v, g)) {
+            for (const auto e : in_edges_range(v, g)) {
                 NFAVertex u = source(e, g);
                 if (regions.at(u) >= split_region && !is_special(u, g)) {
                     assert(contains(orig_to_copy, u));
@@ -1653,7 +1653,7 @@ void implementSomPlan(NG &ng, const ExpressionInfo &expr, u32 comp_id,
 static
 void anchorStarts(NGHolder &g) {
     vector<NFAEdge> dead;
-    for (const auto &e : out_edges_range(g.startDs, g)) {
+    for (const auto e : out_edges_range(g.startDs, g)) {
         NFAVertex v = target(e, g);
         if (v == g.startDs) {
             continue;
@@ -1716,7 +1716,7 @@ void makeSomRevNfaReports(ReportManager &rm, NGHolder &g, NFAVertex sink,
 static
 void clearProperInEdges(NGHolder &g, const NFAVertex sink) {
     vector<NFAEdge> dead;
-    for (const auto &e : in_edges_range(sink, g)) {
+    for (const auto e : in_edges_range(sink, g)) {
         if (source(e, g) == g.accept) {
             continue;
         }
@@ -2420,7 +2420,7 @@ bool splitOffBestLiteral(const NGHolder &g,
  * EXTERNAL_CALLBACK_SOM_PASS reports.
  */
 void makeReportsSomPass(ReportManager &rm, NGHolder &g) {
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         const auto &reports = g[v].reports;
         if (reports.empty()) {
             continue;
diff --git a/src/nfagraph/ng_som_add_redundancy.cpp b/src/nfagraph/ng_som_add_redundancy.cpp
index 33544ec17..b3d188a64 100644
--- a/src/nfagraph/ng_som_add_redundancy.cpp
+++ b/src/nfagraph/ng_som_add_redundancy.cpp
@@ -99,7 +99,7 @@ static
 bool forkVertex(NFAVertex v, NGHolder &g, vector<DepthMinMax> &depths,
                 set<NFAVertex> &dead, size_t *numNewVertices) {
     map<depth, vector<NFAEdge>> predGroups;
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         const DepthMinMax &d = getDepth(source(e, g), g, depths);
         assert(d.min == d.max);
         predGroups[d.min].push_back(e);
@@ -126,7 +126,7 @@ bool forkVertex(NFAVertex v, NGHolder &g, vector<DepthMinMax> &depths,
                      clone_depth.str().c_str());
 
         // Add copies of the out-edges from v.
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             add_edge(clone, target(e, g), g[e], g);
         }
 
diff --git a/src/nfagraph/ng_squash.cpp b/src/nfagraph/ng_squash.cpp
index 03495d144..d220a39f5 100644
--- a/src/nfagraph/ng_squash.cpp
+++ b/src/nfagraph/ng_squash.cpp
@@ -602,7 +602,7 @@ void removeEdgesToAccept(NGHolder &g, NFAVertex v) {
 
     set<NFAEdge> dead;
 
-    for (const auto &e : in_edges_range(g.accept, g)) {
+    for (const auto e : in_edges_range(g.accept, g)) {
         NFAVertex u = source(e, g);
         const auto &r = g[u].reports;
         if (!r.empty() && is_subset_of(r, reports)) {
@@ -611,7 +611,7 @@ void removeEdgesToAccept(NGHolder &g, NFAVertex v) {
         }
     }
 
-    for (const auto &e : in_edges_range(g.acceptEod, g)) {
+    for (const auto e : in_edges_range(g.acceptEod, g)) {
         NFAVertex u = source(e, g);
         const auto &r = g[u].reports;
         if (!r.empty() && is_subset_of(r, reports)) {
diff --git a/src/nfagraph/ng_uncalc_components.cpp b/src/nfagraph/ng_uncalc_components.cpp
index 4ad5ff787..9c1fb52d1 100644
--- a/src/nfagraph/ng_uncalc_components.cpp
+++ b/src/nfagraph/ng_uncalc_components.cpp
@@ -289,7 +289,7 @@ void mergeNfaComponent(NGHolder &dest, const NGHolder &vic, size_t common_len) {
 
     /* add edges */
     DEBUG_PRINTF("common_len=%zu\n", common_len);
-    for (const auto &e : edges_range(vic)) {
+    for (const auto e : edges_range(vic)) {
         NFAVertex u_old = source(e, vic);
         NFAVertex v_old = target(e, vic);
         NFAVertex u = vmap[u_old];
diff --git a/src/nfagraph/ng_util.cpp b/src/nfagraph/ng_util.cpp
index cb2b71035..2cf6887c1 100644
--- a/src/nfagraph/ng_util.cpp
+++ b/src/nfagraph/ng_util.cpp
@@ -124,7 +124,7 @@ NFAVertex clone_vertex(NGHolder &g, NFAVertex v) {
 }
 
 void clone_out_edges(NGHolder &g, NFAVertex source, NFAVertex dest) {
-    for (const auto &e : out_edges_range(source, g)) {
+    for (const auto e : out_edges_range(source, g)) {
         NFAVertex t = target(e, g);
         if (edge(dest, t, g).second) {
             continue;
@@ -137,7 +137,7 @@ void clone_out_edges(NGHolder &g, NFAVertex source, NFAVertex dest) {
 }
 
 void clone_in_edges(NGHolder &g, NFAVertex s, NFAVertex dest) {
-    for (const auto &e : in_edges_range(s, g)) {
+    for (const auto e : in_edges_range(s, g)) {
         NFAVertex ss = source(e, g);
         assert(!edge(ss, dest, g).second);
         NFAEdge clone = add_edge(ss, dest, g);
@@ -362,7 +362,7 @@ void mustBeSetBefore_int(NFAVertex u, const NGHolder &g,
     set<NFAEdge> dead; // Edges leading to u or u's successors.
 
     for (auto v : inv_adjacent_vertices_range(u, g)) {
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             NFAVertex t = target(e, g);
             if (t == u || contains(s, t)) {
                 dead.insert(e);
@@ -415,7 +415,7 @@ void appendLiteral(NGHolder &h, const ue2_literal &s) {
         remove_edge(v, h.accept, h);
     }
 
-    for (const auto &c : s) {
+    for (const auto c : s) {
         NFAVertex v = add_vertex(h);
         h[v].char_reach = c;
         for (auto u : tail) {
@@ -432,14 +432,14 @@ void appendLiteral(NGHolder &h, const ue2_literal &s) {
 
 flat_set<u32> getTops(const NGHolder &h) {
     flat_set<u32> tops;
-    for (const auto &e : out_edges_range(h.start, h)) {
+    for (const auto e : out_edges_range(h.start, h)) {
         insert(&tops, h[e].tops);
     }
     return tops;
 }
 
 void setTops(NGHolder &h, u32 top) {
-    for (const auto &e : out_edges_range(h.start, h)) {
+    for (const auto e : out_edges_range(h.start, h)) {
         assert(h[e].tops.empty());
         if (target(e, h) == h.startDs) {
             continue;
@@ -616,21 +616,21 @@ void reverseHolder(const NGHolder &g_in, NGHolder &g) {
     NFAVertex acceptEod = vertexMap[g_in.start];
 
     // Successors of starts.
-    for (const auto &e : out_edges_range(start, g)) {
+    for (const auto e : out_edges_range(start, g)) {
         NFAVertex v = target(e, g);
         add_edge(g.start, v, g[e], g);
     }
-    for (const auto &e : out_edges_range(startDs, g)) {
+    for (const auto e : out_edges_range(startDs, g)) {
         NFAVertex v = target(e, g);
         add_edge(g.startDs, v, g[e], g);
     }
 
     // Predecessors of accepts.
-    for (const auto &e : in_edges_range(accept, g)) {
+    for (const auto e : in_edges_range(accept, g)) {
         NFAVertex u = source(e, g);
         add_edge(u, g.accept, g[e], g);
     }
-    for (const auto &e : in_edges_range(acceptEod, g)) {
+    for (const auto e : in_edges_range(acceptEod, g)) {
         NFAVertex u = source(e, g);
         add_edge(u, g.acceptEod, g[e], g);
     }
@@ -770,13 +770,13 @@ bool allMatchStatesHaveReports(const NGHolder &g) {
 
 bool isCorrectlyTopped(const NGHolder &g) {
     if (is_triggered(g)) {
-        for (const auto &e : out_edges_range(g.start, g)) {
+        for (const auto e : out_edges_range(g.start, g)) {
             if (g[e].tops.empty() != (target(e, g) == g.startDs)) {
                 return false;
             }
         }
     } else {
-        for (const auto &e : out_edges_range(g.start, g)) {
+        for (const auto e : out_edges_range(g.start, g)) {
             if (!g[e].tops.empty()) {
                 return false;
             }
diff --git a/src/nfagraph/ng_violet.cpp b/src/nfagraph/ng_violet.cpp
index 78d73082a..9d26a5199 100644
--- a/src/nfagraph/ng_violet.cpp
+++ b/src/nfagraph/ng_violet.cpp
@@ -737,7 +737,7 @@ void poisonFromSuccessor(const NGHolder &h, const ue2_literal &succ,
     EdgeSet bad_edges(edge_count);
 
     unordered_map<NFAVertex, EdgeSet> curr;
-    for (const auto &e : in_edges_range(h.accept, h)) {
+    for (const auto e : in_edges_range(h.accept, h)) {
         auto &path_set = curr[source(e, h)];
         if (path_set.empty()) {
             path_set.resize(edge_count);
@@ -757,7 +757,7 @@ void poisonFromSuccessor(const NGHolder &h, const ue2_literal &succ,
                 continue;
             }
             if (overlaps(h[u].char_reach, *it)) {
-                for (const auto &e : in_edges_range(u, h)) {
+                for (const auto e : in_edges_range(u, h)) {
                     auto &new_path_set = next[source(e, h)];
                     if (new_path_set.empty()) {
                         new_path_set.resize(edge_count);
@@ -779,7 +779,7 @@ void poisonFromSuccessor(const NGHolder &h, const ue2_literal &succ,
         DEBUG_PRINTF("poisoning %zu vertices\n", path.second.count());
     }
 
-    for (const auto &e : edges_range(h)) {
+    for (const auto e : edges_range(h)) {
         if (bad_edges.test(h[e].index)) {
             bad.insert(e);
         }
@@ -790,7 +790,7 @@ static
 void poisonForGoodPrefix(const NGHolder &h,
                          const vector<NFAVertexDepth> &depths,
                          flat_set<NFAEdge> &bad, const Grey &grey) {
-    for (const auto &v : vertices_range(h)) {
+    for (const auto v : vertices_range(h)) {
         if (!createsAnchoredLHS(h, {v}, depths, grey)
             && !createsTransientLHS(h, {v}, depths, grey)) {
             insert(&bad, in_edges_range(v, h));
@@ -1503,7 +1503,7 @@ static
 void removeRedundantPrefixes(RoseInGraph &g) {
     STAGE_DEBUG_PRINTF("REMOVING REDUNDANT PREFIXES\n");
 
-    for (const RoseInEdge &e : edges_range(g)) {
+    for (const RoseInEdge e : edges_range(g)) {
         RoseInVertex s = source(e, g);
         RoseInVertex t = target(e, g);
 
@@ -1545,7 +1545,7 @@ void removeRedundantLiteralsFromPrefixes(RoseInGraph &g,
     STAGE_DEBUG_PRINTF("REMOVING LITERALS FROM PREFIXES\n");
 
     vector<RoseInEdge> to_anchor;
-    for (const RoseInEdge &e : edges_range(g)) {
+    for (const RoseInEdge e : edges_range(g)) {
         RoseInVertex s = source(e, g);
         RoseInVertex t = target(e, g);
 
@@ -1755,7 +1755,7 @@ void removeRedundantLiteralsFromInfixes(RoseInGraph &g,
                                         const CompileContext &cc) {
     insertion_ordered_map<NGHolder *, vector<RoseInEdge>> infixes;
 
-    for (const RoseInEdge &e : edges_range(g)) {
+    for (const RoseInEdge e : edges_range(g)) {
         RoseInVertex s = source(e, g);
         RoseInVertex t = target(e, g);
 
@@ -2105,7 +2105,7 @@ void findBetterPrefixes(RoseInGraph &vg, const CompileContext &cc) {
         prefixes.clear();
 
         /* find prefixes */
-        for (const RoseInEdge &e : out_edges_range(start, vg)) {
+        for (const RoseInEdge e : out_edges_range(start, vg)) {
             /* outfixes shouldn't have made it this far */
             assert(vg[target(e, vg)].type == RIV_LITERAL);
             if (vg[e].graph) {
@@ -2167,7 +2167,7 @@ void extractStrongLiterals(RoseInGraph &vg, const CompileContext &cc) {
         changed = false;
 
         edges_by_graph.clear();
-        for (const RoseInEdge &ve : edges_range(vg)) {
+        for (const RoseInEdge ve : edges_range(vg)) {
             if (vg[source(ve, vg)].type != RIV_LITERAL) {
                 continue;
             }
@@ -2247,7 +2247,7 @@ void improveWeakInfixes(RoseInGraph &vg, const CompileContext &cc) {
             continue;
         }
 
-        for (const RoseInEdge &e : out_edges_range(vv, vg)) {
+        for (const RoseInEdge e : out_edges_range(vv, vg)) {
             if (vg[target(e, vg)].type != RIV_LITERAL || !vg[e].graph) {
                 continue;
             }
@@ -2259,7 +2259,7 @@ void improveWeakInfixes(RoseInGraph &vg, const CompileContext &cc) {
     }
 
     insertion_ordered_map<NGHolder *, vector<RoseInEdge>> weak_edges;
-    for (const RoseInEdge &ve : edges_range(vg)) {
+    for (const RoseInEdge ve : edges_range(vg)) {
         NGHolder *h = vg[ve].graph.get();
         if (contains(weak, h)) {
             weak_edges[h].push_back(ve);
@@ -2429,7 +2429,7 @@ void avoidSuffixes(RoseInGraph &vg, const CompileContext &cc) {
     insertion_ordered_map<const NGHolder *, vector<RoseInEdge>> suffixes;
 
     /* find suffixes */
-    for (const RoseInEdge &e : in_edges_range(accept, vg)) {
+    for (const RoseInEdge e : in_edges_range(accept, vg)) {
         /* outfixes shouldn't have made it this far */
         assert(vg[source(e, vg)].type == RIV_LITERAL);
         assert(vg[e].graph); /* non suffix paths should be wired to other
@@ -2527,7 +2527,7 @@ void lookForDoubleCut(RoseInGraph &vg, const CompileContext &cc) {
     }
 
     insertion_ordered_map<const NGHolder *, vector<RoseInEdge>> right_edges;
-    for (const RoseInEdge &ve : edges_range(vg)) {
+    for (const RoseInEdge ve : edges_range(vg)) {
         if (vg[ve].graph && vg[source(ve, vg)].type == RIV_LITERAL) {
             const NGHolder *h = vg[ve].graph.get();
             right_edges[h].push_back(ve);
@@ -2668,7 +2668,7 @@ void decomposeLiteralChains(RoseInGraph &vg, const CompileContext &cc) {
         changed = false;
 
         right_edges.clear();
-        for (const RoseInEdge &ve : edges_range(vg)) {
+        for (const RoseInEdge ve : edges_range(vg)) {
             if (vg[ve].graph && vg[source(ve, vg)].type == RIV_LITERAL) {
                 const NGHolder *h = vg[ve].graph.get();
                 right_edges[h].push_back(ve);
@@ -2718,7 +2718,7 @@ void lookForCleanEarlySplits(RoseInGraph &vg, const CompileContext &cc) {
 
         insertion_ordered_map<const NGHolder *, vector<RoseInEdge>> rightfixes;
         for (RoseInVertex v : curr) {
-            for (const RoseInEdge &e : out_edges_range(v, vg)) {
+            for (const RoseInEdge e : out_edges_range(v, vg)) {
                 if (vg[e].graph) {
                     NGHolder *h = vg[e].graph.get();
                     rightfixes[h].push_back(e);
@@ -2742,7 +2742,7 @@ void rehomeEodSuffixes(RoseInGraph &vg) {
     // Find edges to accept with EOD-anchored graphs that we can move over to
     // acceptEod.
     vector<RoseInEdge> acc_edges;
-    for (const auto &e : edges_range(vg)) {
+    for (const auto e : edges_range(vg)) {
         if (vg[target(e, vg)].type != RIV_ACCEPT) {
             continue;
         }
@@ -2908,7 +2908,7 @@ bool ensureImplementable(RoseBuild &rose, RoseInGraph &vg, bool allow_changes,
         DEBUG_PRINTF("added %u\n", added_count);
         insertion_ordered_map<shared_ptr<NGHolder>,
                               vector<RoseInEdge>> edges_by_graph;
-        for (const RoseInEdge &ve : edges_range(vg)) {
+        for (const RoseInEdge ve : edges_range(vg)) {
             if (vg[ve].graph && !vg[ve].dfa) {
                 auto &h = vg[ve].graph;
                 edges_by_graph[h].push_back(ve);
diff --git a/src/rose/rose_build_add.cpp b/src/rose/rose_build_add.cpp
index aa043fade..4f850ccee 100644
--- a/src/rose/rose_build_add.cpp
+++ b/src/rose/rose_build_add.cpp
@@ -179,7 +179,7 @@ RoseVertex duplicate(RoseBuildImpl *build, RoseVertex v) {
         build->literal_info[lit_id].vertices.insert(w);
     }
 
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         RoseVertex s = source(e, g);
         add_edge(s, w, g[e], g);
         DEBUG_PRINTF("added edge (%zu,%zu)\n", g[s].index, g[w].index);
@@ -600,7 +600,7 @@ void doRoseLiteralVertex(RoseBuildImpl *tbi, bool use_eod_table,
 
         /* need to check if putting iv into the anchored table would create
          * any bad_overlap relationships with its successor literals */
-        for (const auto &e : out_edges_range(iv, ig)) {
+        for (const auto e : out_edges_range(iv, ig)) {
             RoseInVertex t = target(e, ig);
             u32 overlap = findRoseAnchorFloatingOverlap(ig[e], ig[t]);
             DEBUG_PRINTF("found overlap of %u\n", overlap);
@@ -650,7 +650,7 @@ unique_ptr<NGHolder> makeRoseEodPrefix(const NGHolder &h, RoseBuildImpl &build,
 
     // Move acceptEod edges over to accept.
     vector<NFAEdge> dead;
-    for (const auto &e : in_edges_range(g.acceptEod, g)) {
+    for (const auto e : in_edges_range(g.acceptEod, g)) {
         NFAVertex u = source(e, g);
         if (u == g.accept) {
             continue;
@@ -834,7 +834,7 @@ bool suitableForEod(const RoseInGraph &ig, vector<RoseInVertex> topo,
 
         if (ig[v].type == RIV_ACCEPT) {
             DEBUG_PRINTF("[ACCEPT]\n");
-            for (const auto &e : in_edges_range(v, ig)) {
+            for (const auto e : in_edges_range(v, ig)) {
                 if (!ig[e].graph || !can_only_match_at_eod(*ig[e].graph)) {
                     DEBUG_PRINTF("floating accept\n");
                     return false;
@@ -863,7 +863,7 @@ bool suitableForEod(const RoseInGraph &ig, vector<RoseInVertex> topo,
             return false;
         }
 
-        for (const auto &e : out_edges_range(v, ig)) {
+        for (const auto e : out_edges_range(v, ig)) {
             RoseInVertex t = target(e, ig);
 
             assert(contains(max_depth_from_eod, t));
@@ -976,7 +976,7 @@ void populateRoseGraph(RoseBuildImpl *tbi, RoseBuildData &bd) {
         }
 
         vector<pair<RoseVertex, RoseInEdge> > parents;
-        for (const auto &e : in_edges_range(iv, ig)) {
+        for (const auto e : in_edges_range(iv, ig)) {
             RoseInVertex u = source(e, ig);
             assert(contains(vertex_map, u));
             const vector<RoseVertex> &images = vertex_map[u];
@@ -1058,7 +1058,7 @@ static
 bool predsAreDelaySensitive(const RoseInGraph &ig, RoseInVertex v) {
     assert(in_degree(v, ig));
 
-    for (const auto &e : in_edges_range(v, ig)) {
+    for (const auto e : in_edges_range(v, ig)) {
         if (ig[e].graph || ig[e].haig) {
             DEBUG_PRINTF("edge graph\n");
             return true;
@@ -1126,7 +1126,7 @@ u32 findMaxSafeDelay(const RoseInGraph &ig, RoseInVertex u, RoseInVertex v) {
     DEBUG_PRINTF("max safe delay for this edge: %zu\n", max_delay);
 
     // Now consider the predecessors of u.
-    for (const auto &e : in_edges_range(u, ig)) {
+    for (const auto e : in_edges_range(u, ig)) {
         RoseInVertex w = source(e, ig);
         if (ig[w].type == RIV_START) {
             continue;
@@ -1342,7 +1342,7 @@ void transformAnchoredLiteralOverlap(RoseInGraph &ig, RoseBuildData &bd,
         return;
     }
 
-    for (const auto &e : edges_range(ig)) {
+    for (const auto e : edges_range(ig)) {
         const RoseInVertex u = source(e, ig);
         const RoseInVertex v = target(e, ig);
 
@@ -1494,7 +1494,7 @@ void transformSuffixDelay(RoseInGraph &ig, const CompileContext &cc) {
 #ifndef NDEBUG
 static
 bool validateKinds(const RoseInGraph &g) {
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (g[e].graph && g[e].graph->kind != whatRoseIsThis(g, e)) {
             return false;
         }
@@ -1528,7 +1528,7 @@ bool RoseBuildImpl::addRose(const RoseInGraph &ig, bool prefilter) {
 
     insertion_ordered_map<NGHolder *, vector<RoseInEdge>> graphs;
 
-    for (const auto &e : edges_range(in)) {
+    for (const auto e : edges_range(in)) {
         if (!in[e].graph) {
             assert(!in[e].dfa);
             assert(!in[e].haig);
@@ -1589,7 +1589,7 @@ bool RoseBuildImpl::addSombeRose(const RoseInGraph &ig) {
 
     RoseBuildData bd(ig, true);
 
-    for (const auto &e : edges_range(ig)) {
+    for (const auto e : edges_range(ig)) {
         if (!ig[e].graph) {
             continue; // no graph
         }
@@ -1614,7 +1614,7 @@ bool roseCheckRose(const RoseInGraph &ig, bool prefilter,
 
     vector<NGHolder *> graphs;
 
-    for (const auto &e : edges_range(ig)) {
+    for (const auto e : edges_range(ig)) {
         if (!ig[e].graph) {
             continue; // no graph
         }
diff --git a/src/rose/rose_build_bytecode.cpp b/src/rose/rose_build_bytecode.cpp
index df464c280..01f03de1f 100644
--- a/src/rose/rose_build_bytecode.cpp
+++ b/src/rose/rose_build_bytecode.cpp
@@ -485,7 +485,7 @@ bool nfaStuckOn(const NGHolder &g) {
     set<u32> tops;
     set<u32> done_tops;
 
-    for (const auto &e : out_edges_range(g.start, g)) {
+    for (const auto e : out_edges_range(g.start, g)) {
         insert(&tops, g[e].tops);
         if (!g[target(e, g)].char_reach.all()) {
             continue;
@@ -736,7 +736,7 @@ void findInfixTriggers(const RoseBuildImpl &build,
 
         set<PredTopPair> &triggers = (*infixTriggers)[left_id(g[v].left)];
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             RoseVertex u = source(e, g);
             if (build.isAnyStart(u)) {
                 continue;
@@ -1212,7 +1212,7 @@ unique_ptr<TamaInfo> constructTamaInfo(const RoseGraph &g,
             if (is_suffix) {
                 tops.insert(g[v].suffix.top);
             } else {
-                for (const auto &e : in_edges_range(v, g)) {
+                for (const auto e : in_edges_range(v, g)) {
                     tops.insert(g[e].rose_top);
                 }
             }
@@ -1235,7 +1235,7 @@ void updateTops(const RoseGraph &g, const TamaInfo &tamaInfo,
             if (is_suffix) {
                 tamaProto.add(n, g[v].index, g[v].suffix.top, out_top_remap);
             } else {
-                for (const auto &e : in_edges_range(v, g)) {
+                for (const auto e : in_edges_range(v, g)) {
                     tamaProto.add(n, g[v].index, g[e].rose_top, out_top_remap);
                 }
             }
@@ -2374,7 +2374,7 @@ void recordResources(RoseResources &resources, const RoseBuildImpl &build,
     resources.has_literals = !fragments.empty();
 
     const auto &g = build.g;
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (g[v].eod_accept) {
             resources.has_eod = true;
             break;
@@ -2607,7 +2607,7 @@ unordered_map<RoseVertex, u32> assignStateIndices(const RoseBuildImpl &build) {
         // We only need a state index if we have successors that are not
         // eagerly-reported EOD vertices.
         bool needs_state_index = false;
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             if (!canEagerlyReportAtEod(build, e)) {
                 needs_state_index = true;
                 break;
@@ -2768,7 +2768,7 @@ vector<vector<RoseEdge>> findEdgesByLiteral(const RoseBuildImpl &build) {
     vector<vector<RoseEdge>> lit_edge_map(build.literals.size());
 
     const auto &g = build.g;
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         for (const auto &lit_id : g[v].literals) {
             assert(lit_id < lit_edge_map.size());
             auto &edge_list = lit_edge_map.at(lit_id);
@@ -3266,7 +3266,7 @@ void addEodAnchorProgram(const RoseBuildImpl &build, const build_context &bc,
                      in_degree(v, g));
 
         vector<RoseEdge> edge_list;
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             RoseVertex u = source(e, g);
             if (build.isInETable(u) != in_etable) {
                 DEBUG_PRINTF("pred %zu %s in etable\n", g[u].index,
@@ -3310,7 +3310,7 @@ void addEodEventProgram(const RoseBuildImpl &build, build_context &bc,
     // Collect all edges leading into EOD event literal vertices.
     vector<RoseEdge> edge_list;
     for (const auto &v : lit_info.vertices) {
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             edge_list.push_back(e);
         }
     }
diff --git a/src/rose/rose_build_castle.cpp b/src/rose/rose_build_castle.cpp
index 59bab3b1f..1a81807bf 100644
--- a/src/rose/rose_build_castle.cpp
+++ b/src/rose/rose_build_castle.cpp
@@ -328,7 +328,7 @@ void remapCastleTops(RoseBuildImpl &tbi) {
 
         // Update the tops on the edges leading into vertices in v.
         for (auto v : verts) {
-            for (const auto &e : in_edges_range(v, g)) {
+            for (const auto e : in_edges_range(v, g)) {
                 g[e].rose_top = top_map.at(g[e].rose_top);
             }
         }
@@ -372,7 +372,7 @@ bool triggerKillsRoseCastle(const RoseBuildImpl &tbi, const left_id &left,
         DEBUG_PRINTF("s=%s, castle reach=%s\n", dumpString(s).c_str(),
                       describeClass(cr).c_str());
 
-        for (const auto &s_cr : s) {
+        for (const auto s_cr : s) {
             if (!overlaps(cr, s_cr)) {
                 DEBUG_PRINTF("reach %s kills castle\n",
                              describeClass(s_cr).c_str());
diff --git a/src/rose/rose_build_compile.cpp b/src/rose/rose_build_compile.cpp
index 1cf3bbe69..2ac3ea672 100644
--- a/src/rose/rose_build_compile.cpp
+++ b/src/rose/rose_build_compile.cpp
@@ -94,7 +94,7 @@ static
 bool limited_explosion(const ue2_literal &s) {
     u32 nc_count = 0;
 
-    for (const auto &e : s) {
+    for (const auto e : s) {
         if (e.nocase) {
             nc_count++;
         }
@@ -268,7 +268,7 @@ bool RoseBuildImpl::isPseudoStarOrFirstOnly(const RoseEdge &e) const {
 }
 
 bool RoseBuildImpl::hasOnlyPseudoStarInEdges(RoseVertex v) const {
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         if (!isPseudoStar(e)) {
             return false;
         }
@@ -369,7 +369,7 @@ RoseRoleHistory findHistoryScheme(const RoseBuildImpl &tbi, const RoseEdge &e) {
 
 static
 void assignHistories(RoseBuildImpl &tbi) {
-    for (const auto &e : edges_range(tbi.g)) {
+    for (const auto e : edges_range(tbi.g)) {
         if (tbi.g[e].history == ROSE_ROLE_HISTORY_INVALID) {
             tbi.g[e].history = findHistoryScheme(tbi, e);
         }
@@ -622,7 +622,7 @@ bool promoteEodToAnchored(RoseBuildImpl &tbi, const vector<u32> &eodLiterals) {
         auto &eod_verts = tbi.literal_info[eod_id].vertices;
 
         for (auto v : eod_verts) {
-            for (const auto &e : in_edges_range(v, tbi.g)) {
+            for (const auto e : in_edges_range(v, tbi.g)) {
                 assert(tbi.g[e].maxBound != ROSE_BOUND_INF);
                 tbi.g[e].minBound += lit.s.length();
                 tbi.g[e].maxBound += lit.s.length();
@@ -1011,7 +1011,7 @@ void packInfixTops(NGHolder &h, RoseGraph &g,
     for (auto v : verts) {
         assert(g[v].left.graph.get() == &h);
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             u32 top = g[e].rose_top;
             used_tops.insert(top);
         }
@@ -1026,13 +1026,13 @@ void packInfixTops(NGHolder &h, RoseGraph &g,
     for (auto v : verts) {
         assert(g[v].left.graph.get() == &h);
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             g[e].rose_top = top_mapping.at(g[e].rose_top);
         }
     }
 
     vector<NFAEdge> dead;
-    for (const auto &e : out_edges_range(h.start, h)) {
+    for (const auto e : out_edges_range(h.start, h)) {
         NFAVertex v = target(e, h);
         if (v == h.startDs) {
             continue; // stylised edge, leave it alone.
@@ -1157,7 +1157,7 @@ void findTopTriggerCancels(RoseBuildImpl &build) {
         set<u32> pred_lit_ids;
 
         for (auto v : succs) {
-            for (const auto &e : in_edges_range(v, build.g)) {
+            for (const auto e : in_edges_range(v, build.g)) {
                 RoseVertex u = source(e, build.g);
                 tops_seen.insert(build.g[e].rose_top);
                 insert(&pred_lit_ids, build.g[u].literals);
@@ -1620,7 +1620,7 @@ void addAnchoredSmallBlockLiterals(RoseBuildImpl &tbi) {
 #ifndef NDEBUG
 static
 bool historiesAreValid(const RoseGraph &g) {
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         if (g[e].history == ROSE_ROLE_HISTORY_INVALID) {
             DEBUG_PRINTF("edge [%zu,%zu] has invalid history\n",
                          g[source(e, g)].index, g[target(e, g)].index);
diff --git a/src/rose/rose_build_convert.cpp b/src/rose/rose_build_convert.cpp
index 33351099f..0d4a54c70 100644
--- a/src/rose/rose_build_convert.cpp
+++ b/src/rose/rose_build_convert.cpp
@@ -117,7 +117,7 @@ unique_ptr<NGHolder> makeRosePrefix(const ue2_literal &s) {
     unique_ptr<NGHolder> h = ue2::make_unique<NGHolder>(NFA_PREFIX);
 
     NFAVertex u = h->startDs;
-    for (const auto &c : s) {
+    for (const auto c : s) {
         NFAVertex v = addHolderVertex(c, *h);
         add_edge(u, v, *h);
         u = v;
@@ -628,7 +628,7 @@ void convertPrefixToBounds(RoseBuildImpl &tbi) {
 
     /* graphs with prefixes produced by rose are wired to tbi.root */
 
-    for (const auto &e : out_edges_range(tbi.root, g)) {
+    for (const auto e : out_edges_range(tbi.root, g)) {
         RoseVertex v = target(e, g);
 
         if (in_degree(v, g) != 1) {
@@ -673,7 +673,7 @@ void convertPrefixToBounds(RoseBuildImpl &tbi) {
         handleMixedPrefixCliche(h, g, v, e, ar, &to_delete, tbi.cc);
     }
 
-    for (const auto &e : out_edges_range(ar, g)) {
+    for (const auto e : out_edges_range(ar, g)) {
         RoseVertex v = target(e, g);
 
         /* note: vertices that we have rehomed will currently have an in-degree
diff --git a/src/rose/rose_build_dump.cpp b/src/rose/rose_build_dump.cpp
index dbc938a5c..6538875e4 100644
--- a/src/rose/rose_build_dump.cpp
+++ b/src/rose/rose_build_dump.cpp
@@ -441,7 +441,7 @@ void dumpRoseLiterals(const RoseBuildImpl &build,
             os << ", min_offset=" << g[v].min_offset;
             os << ", max_offset=" << g[v].max_offset << endl;
             // pred info
-            for (const auto &ie : in_edges_range(v, g)) {
+            for (const auto ie : in_edges_range(v, g)) {
                 const auto &u = source(ie, g);
                 os << "    Predecessor index=";
                 if (u == build.root) {
diff --git a/src/rose/rose_build_exclusive.cpp b/src/rose/rose_build_exclusive.cpp
index 6a5a710d0..4d2f0efe5 100644
--- a/src/rose/rose_build_exclusive.cpp
+++ b/src/rose/rose_build_exclusive.cpp
@@ -53,7 +53,7 @@ struct RoleChunk {
 static
 CharReach getReachability(const NGHolder &h) {
     CharReach cr;
-    for (const auto &v : vertices_range(h)) {
+    for (const auto v : vertices_range(h)) {
         if (!is_special(v, h)) {
             cr |= h[v].char_reach;
         }
diff --git a/src/rose/rose_build_groups.cpp b/src/rose/rose_build_groups.cpp
index 209889e55..699fda855 100644
--- a/src/rose/rose_build_groups.cpp
+++ b/src/rose/rose_build_groups.cpp
@@ -611,7 +611,7 @@ bool isGroupSquasher(const RoseBuildImpl &build, const u32 id /* literal id */,
         }
 
         // Out-edges must have inf max bound, + no other shenanigans */
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             if (g[e].maxBound != ROSE_BOUND_INF) {
                 return false;
             }
@@ -650,7 +650,7 @@ bool isGroupSquasher(const RoseBuildImpl &build, const u32 id /* literal id */,
 
         // Out-edges must have inf max bound and not directly lead to another
         // vertex with this group, e.g. 'foobar.*foobar'.
-        for (const auto &e : out_edges_range(v, g)) {
+        for (const auto e : out_edges_range(v, g)) {
             if (g[e].maxBound != ROSE_BOUND_INF) {
                 return false;
             }
@@ -671,7 +671,7 @@ bool isGroupSquasher(const RoseBuildImpl &build, const u32 id /* literal id */,
         // In-edges must all be dot-stars with no overlap at all, as overlap
         // also causes history to be used.
         /* Different tables are already forbidden by previous checks */
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             if (!(g[e].minBound == 0 && g[e].maxBound == ROSE_BOUND_INF)) {
                 return false;
             }
diff --git a/src/rose/rose_build_infix.cpp b/src/rose/rose_build_infix.cpp
index 80e125423..2c083a2ed 100644
--- a/src/rose/rose_build_infix.cpp
+++ b/src/rose/rose_build_infix.cpp
@@ -150,7 +150,7 @@ u32 findMaxLiteralMatches(const NGHolder &h, const set<ue2_literal> &lits) {
     // The set of all edges in the graph is used for existence checks in
     // contractVertex.
     EdgeCache all_edges;
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         all_edges.emplace(source(e, g), target(e, g));
     }
 
diff --git a/src/rose/rose_build_lookaround.cpp b/src/rose/rose_build_lookaround.cpp
index d0540d79b..83c439fe8 100644
--- a/src/rose/rose_build_lookaround.cpp
+++ b/src/rose/rose_build_lookaround.cpp
@@ -82,7 +82,7 @@ void getForwardReach(const NGHolder &g, u32 top, map<s32, CharReach> &look) {
     flat_set<NFAVertex> curr, next;
 
     // Consider only successors of start with the required top.
-    for (const auto &e : out_edges_range(g.start, g)) {
+    for (const auto e : out_edges_range(g.start, g)) {
         NFAVertex v = target(e, g);
         if (v == g.startDs) {
             continue;
@@ -273,7 +273,7 @@ void findForwardReach(const RoseGraph &g, const RoseVertex v,
     // Non-leaf vertices can pick up a mask per successor prefix rose
     // engine.
     vector<map<s32, CharReach>> rose_look;
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         RoseVertex t = target(e, g);
         if (!g[t].left) {
             DEBUG_PRINTF("successor %zu has no leftfix\n", g[t].index);
@@ -476,7 +476,7 @@ vector<LookProto> findLiteralReach(const rose_literal_id &lit) {
     look.reserve(lit.s.length());
 
     s32 i = 0 - lit.s.length() - lit.delay;
-    for (const auto &c : lit.s) {
+    for (const auto c : lit.s) {
         look.emplace_back(i, c);
         i++;
     }
diff --git a/src/rose/rose_build_matchers.cpp b/src/rose/rose_build_matchers.cpp
index 4fde4c441..72b934817 100644
--- a/src/rose/rose_build_matchers.cpp
+++ b/src/rose/rose_build_matchers.cpp
@@ -493,7 +493,7 @@ bool isNoRunsVertex(const RoseBuildImpl &build, RoseVertex u) {
         return false;
     }
 
-    for (const auto &oe : out_edges_range(u, g)) {
+    for (const auto oe : out_edges_range(u, g)) {
         RoseVertex v = target(oe, g);
         if (g[oe].maxBound != ROSE_BOUND_INF) {
             DEBUG_PRINTF("edge (%zu,%zu) has max bound\n", g[u].index,
diff --git a/src/rose/rose_build_merge.cpp b/src/rose/rose_build_merge.cpp
index 5066dbd57..3c76ffa48 100644
--- a/src/rose/rose_build_merge.cpp
+++ b/src/rose/rose_build_merge.cpp
@@ -1018,7 +1018,7 @@ bool mergeLeftfixPair(RoseBuildImpl &build, left_id &r1, left_id &r2,
         const shared_ptr<CastleProto> &c = g[verts2.front()].left.castle;
         for (RoseVertex v : verts1) {
             g[v].left.castle = c;
-            for (const auto &e : in_edges_range(v, g)) {
+            for (const auto e : in_edges_range(v, g)) {
                 g[e].rose_top = top_map.at(g[e].rose_top);
             }
         }
@@ -1549,7 +1549,7 @@ struct DedupeLeftKey {
 static
 flat_set<pair<size_t, u32>> get_pred_tops(RoseVertex v, const RoseGraph &g) {
     flat_set<pair<size_t, u32>> preds;
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         preds.emplace(g[source(e, g)].index, g[e].rose_top);
     }
     return preds;
@@ -1683,7 +1683,7 @@ u32 findUnusedTop(const flat_set<u32> &tops) {
 // Replace top 't' on edges with new top 'u'.
 static
 void replaceTops(NGHolder &h, const map<u32, u32> &top_mapping) {
-    for (const auto &e : out_edges_range(h.start, h)) {
+    for (const auto e : out_edges_range(h.start, h)) {
         NFAVertex v = target(e, h);
         if (v == h.startDs) {
             continue;
@@ -1741,7 +1741,7 @@ bool setDistinctRoseTops(RoseGraph &g, NGHolder &h1, const NGHolder &h2,
         DEBUG_PRINTF("vertex %zu\n", g[v].index);
         assert(!g[v].left.haig);
         assert(!g[v].left.dfa);
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             u32 t = g[e].rose_top;
             DEBUG_PRINTF("t=%u\n", t);
             assert(contains(top_mapping, t));
@@ -1843,7 +1843,7 @@ void mergeNfaLeftfixes(RoseBuildImpl &tbi, LeftfixBouquet &roses) {
             // back.
             map<RoseEdge, RoseEdgeProps> edge_props;
             for (auto v : verts2) {
-                for (const auto &e : in_edges_range(v, g)) {
+                for (const auto e : in_edges_range(v, g)) {
                     edge_props[e] = g[e];
                 }
             }
@@ -2009,7 +2009,7 @@ void mergeCastleChunk(RoseBuildImpl &build, vector<left_id> &cands,
             for (auto v : verts_2) {
                 assert(g[v].left.castle.get() == cand_2.castle());
                 g[v].left.castle = winner;
-                for (const auto &e : in_edges_range(v, g)) {
+                for (const auto e : in_edges_range(v, g)) {
                     g[e].rose_top = top_map.at(g[e].rose_top);
                 }
             }
diff --git a/src/rose/rose_build_misc.cpp b/src/rose/rose_build_misc.cpp
index 0b0e689c9..f3e1cfc05 100644
--- a/src/rose/rose_build_misc.cpp
+++ b/src/rose/rose_build_misc.cpp
@@ -125,7 +125,7 @@ bool RoseBuildImpl::isNonRootSuccessor(const RoseVertex &v) const {
 }
 
 bool hasAnchHistorySucc(const RoseGraph &g, RoseVertex v) {
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         if (g[e].history == ROSE_ROLE_HISTORY_ANCH) {
             return true;
         }
@@ -135,7 +135,7 @@ bool hasAnchHistorySucc(const RoseGraph &g, RoseVertex v) {
 }
 
 bool hasLastByteHistorySucc(const RoseGraph &g, RoseVertex v) {
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         if (g[e].history == ROSE_ROLE_HISTORY_LAST_BYTE) {
             return true;
         }
@@ -338,7 +338,7 @@ void RoseBuildImpl::removeVertices(const vector<RoseVertex> &dead) {
 // those via infixes.
 u32 RoseBuildImpl::calcSuccMaxBound(RoseVertex u) const {
     u32 maxBound = 0;
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         RoseVertex v = target(e, g);
 
         if (g[v].left) {
@@ -510,7 +510,7 @@ bool roseHasTops(const RoseBuildImpl &build, RoseVertex v) {
 
     set<u32> graph_tops;
     if (!build.isRootSuccessor(v)) {
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             graph_tops.insert(g[e].rose_top);
         }
     }
@@ -1008,7 +1008,7 @@ bool hasOrphanedTops(const RoseBuildImpl &build) {
             set<u32> &tops = leftfixes[g[v].left];
             if (!build.isRootSuccessor(v)) {
                 // Tops for infixes come from the in-edges.
-                for (const auto &e : in_edges_range(v, g)) {
+                for (const auto e : in_edges_range(v, g)) {
                     tops.insert(g[e].rose_top);
                 }
             }
diff --git a/src/rose/rose_build_program.cpp b/src/rose/rose_build_program.cpp
index 96c95dbf0..2888e312f 100644
--- a/src/rose/rose_build_program.cpp
+++ b/src/rose/rose_build_program.cpp
@@ -904,7 +904,7 @@ void makeRoleGroups(const RoseGraph &g, ProgramBuild &prog_build,
     // intersection of the groups set by our predecessors.
     assert(in_degree(v, g) > 0);
     rose_group already_on = ~rose_group{0};
-    for (const auto &u : inv_adjacent_vertices_range(v, g)) {
+    for (const auto u : inv_adjacent_vertices_range(v, g)) {
         already_on &= prog_build.vertex_group_map.at(u);
     }
 
@@ -1152,7 +1152,7 @@ static really_inline
 void nibUpdate(map<u32, u16> &nib, u32 hi_lo) {
     u16 hi = hi_lo >> 16;
     u16 lo = hi_lo & 0xffff;
-    for (const auto pairs : nib) {
+    for (const auto &pairs : nib) {
         u32 old = pairs.first;
         if ((old >> 16) == hi || (old & 0xffff) == lo) {
             if (!nib[old | hi_lo]) {
@@ -1958,7 +1958,7 @@ void makeRoleInfixTriggers(const RoseBuildImpl &build,
 
     vector<TriggerInfo> triggers;
 
-    for (const auto &e : out_edges_range(u, g)) {
+    for (const auto e : out_edges_range(u, g)) {
         RoseVertex v = target(e, g);
         if (!g[v].left) {
             continue;
@@ -2011,7 +2011,7 @@ bool onlyAtEod(const RoseBuildImpl &tbi, RoseVertex v) {
         return false;
     }
 
-    for (const auto &e : out_edges_range(v, g)) {
+    for (const auto e : out_edges_range(v, g)) {
         RoseVertex w = target(e, g);
         if (!g[w].eod_accept) {
             return false;
@@ -2049,7 +2049,7 @@ void makeRoleEagerEodReports(const RoseBuildImpl &build,
                          RoseProgram &program) {
     RoseProgram eod_program;
 
-    for (const auto &e : out_edges_range(v, build.g)) {
+    for (const auto e : out_edges_range(v, build.g)) {
         if (canEagerlyReportAtEod(build, e)) {
             RoseProgram block;
             makeRoleReports(build, leftfix_info, needs_catchup,
diff --git a/src/rose/rose_build_role_aliasing.cpp b/src/rose/rose_build_role_aliasing.cpp
index 359550e11..03ff433ae 100644
--- a/src/rose/rose_build_role_aliasing.cpp
+++ b/src/rose/rose_build_role_aliasing.cpp
@@ -194,11 +194,11 @@ bool sameSuccessors(RoseVertex a, RoseVertex b, const RoseGraph &g) {
 
     set<AliasOutEdge> succs_a, succs_b;
 
-    for (const auto &e : out_edges_range(a, g)) {
+    for (const auto e : out_edges_range(a, g)) {
         succs_a.insert(AliasOutEdge(e, g));
     }
 
-    for (const auto &e : out_edges_range(b, g)) {
+    for (const auto e : out_edges_range(b, g)) {
         succs_b.insert(AliasOutEdge(e, g));
     }
 
@@ -241,11 +241,11 @@ bool samePredecessors(RoseVertex a, RoseVertex b, const RoseGraph &g) {
 
     set<AliasInEdge> preds_a, preds_b;
 
-    for (const auto &e : in_edges_range(a, g)) {
+    for (const auto e : in_edges_range(a, g)) {
         preds_a.insert(AliasInEdge(e, g));
     }
 
-    for (const auto &e : in_edges_range(b, g)) {
+    for (const auto e : in_edges_range(b, g)) {
         preds_b.insert(AliasInEdge(e, g));
     }
 
@@ -258,7 +258,7 @@ bool samePredecessors(RoseVertex a, RoseVertex b, const RoseGraph &g) {
             return false;
         }
 
-        for (const auto &e_a : in_edges_range(a, g)) {
+        for (const auto e_a : in_edges_range(a, g)) {
             RoseEdge e = edge(source(e_a, g), b, g);
             if (!e || g[e].rose_top != g[e_a].rose_top) {
                 DEBUG_PRINTF("bad tops\n");
@@ -273,7 +273,7 @@ bool samePredecessors(RoseVertex a, RoseVertex b, const RoseGraph &g) {
 static
 bool hasCommonSuccWithBadBounds(RoseVertex a, RoseVertex b,
                                 const RoseGraph &g) {
-    for (const auto &e_a : out_edges_range(a, g)) {
+    for (const auto e_a : out_edges_range(a, g)) {
         if (RoseEdge e = edge(b, target(e_a, g), g)) {
             if (g[e_a].maxBound < g[e].minBound
                 || g[e].maxBound < g[e_a].minBound) {
@@ -292,7 +292,7 @@ bool hasCommonSuccWithBadBounds(RoseVertex a, RoseVertex b,
 static
 bool hasCommonPredWithBadBounds(RoseVertex a, RoseVertex b,
                                 const RoseGraph &g) {
-    for (const auto &e_a : in_edges_range(a, g)) {
+    for (const auto e_a : in_edges_range(a, g)) {
         if (RoseEdge e = edge(source(e_a, g), b, g)) {
             if (g[e_a].maxBound < g[e].minBound
                 || g[e].maxBound < g[e_a].minBound) {
@@ -482,7 +482,7 @@ void mergeEdges(RoseVertex a, RoseVertex b, RoseGraph &g) {
     EdgeCache b_edges;
 
     // Cache b's in-edges so we can look them up by source quickly.
-    for (const auto &e : in_edges_range(b, g)) {
+    for (const auto e : in_edges_range(b, g)) {
         RoseVertex u = source(e, g);
         b_edges.emplace(u, e);
     }
@@ -501,7 +501,7 @@ void mergeEdges(RoseVertex a, RoseVertex b, RoseGraph &g) {
 
     // Cache b's out-edges so we can look them up by target quickly.
     b_edges.clear();
-    for (const auto &e : out_edges_range(b, g)) {
+    for (const auto e : out_edges_range(b, g)) {
         RoseVertex v = target(e, g);
         b_edges.emplace(v, e);
     }
@@ -699,7 +699,7 @@ bool hasCommonPredWithDiffRoses(RoseVertex a, RoseVertex b,
 
     const bool equal_roses = hasEqualLeftfixes(a, b, g);
 
-    for (const auto &e_a : in_edges_range(a, g)) {
+    for (const auto e_a : in_edges_range(a, g)) {
         if (RoseEdge e = edge(source(e_a, g), b, g)) {
             DEBUG_PRINTF("common pred, e_r=%d r_t %u,%u\n",
                          (int)equal_roses, g[e].rose_top, g[e_a].rose_top);
@@ -784,7 +784,7 @@ void setReports(CastleProto &castle, ReportID report) {
 
 static
 void updateEdgeTops(RoseGraph &g, RoseVertex v, const map<u32, u32> &top_map) {
-    for (const auto &e : in_edges_range(v, g)) {
+    for (const auto e : in_edges_range(v, g)) {
         g[e].rose_top = top_map.at(g[e].rose_top);
     }
 }
@@ -796,7 +796,7 @@ void pruneUnusedTops(CastleProto &castle, const RoseGraph &g,
     for (auto v : verts) {
         assert(g[v].left.castle.get() == &castle);
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             u32 top = g[e].rose_top;
             assert(contains(castle.repeats, top));
             used_tops.insert(top);
@@ -827,14 +827,14 @@ void pruneUnusedTops(NGHolder &h, const RoseGraph &g,
     for (auto v : verts) {
         assert(g[v].left.graph.get() == &h);
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             u32 top = g[e].rose_top;
             used_tops.insert(top);
         }
     }
 
     vector<NFAEdge> dead;
-    for (const auto &e : out_edges_range(h.start, h)) {
+    for (const auto e : out_edges_range(h.start, h)) {
         NFAVertex v = target(e, h);
         if (v == h.startDs) {
             continue; // stylised edge, leave it alone.
@@ -1068,7 +1068,7 @@ bool attemptRoseCastleMerge(RoseBuildImpl &build, bool preds_same, RoseVertex a,
     // Merge in the relevant repeats from b with the new report. Note that
     // we'll have to remap tops appropriately.
     map<u32, u32> b_top_map;
-    for (const auto &e : in_edges_range(b, g)) {
+    for (const auto e : in_edges_range(b, g)) {
         u32 top = g[e].rose_top;
         assert(contains(b_castle.repeats, top));
 
@@ -1288,7 +1288,7 @@ bool attemptRoseGraphMerge(RoseBuildImpl &build, bool preds_same, RoseVertex a,
     pruneAllOtherReports(victim, new_report);
 
     map<RoseVertex, RoseEdgeProps> a_props;
-    for (const auto &e : in_edges_range(a, g)) {
+    for (const auto e : in_edges_range(a, g)) {
         a_props[source(e, g)] = g[e];
     }
 
@@ -1307,7 +1307,7 @@ bool attemptRoseGraphMerge(RoseBuildImpl &build, bool preds_same, RoseVertex a,
     if (!mergeNfaPair(victim, *b_h, nullptr, build.cc)) {
         DEBUG_PRINTF("merge failed\n");
         // Restore in-edge properties.
-        for (const auto &e : in_edges_range(a, g)) {
+        for (const auto e : in_edges_range(a, g)) {
             g[e] = a_props[source(e, g)];
         }
         assert(roseHasTops(build, a));
@@ -1941,7 +1941,7 @@ static
 bool hasNoDiamondSiblings(const RoseGraph &g, RoseVertex v) {
     if (has_successor(v, g)) {
         bool only_succ = true;
-        for (const auto &w : adjacent_vertices_range(v, g)) {
+        for (const auto w : adjacent_vertices_range(v, g)) {
             if (in_degree(w, g) > 1) {
                 only_succ = false;
                 break;
@@ -1957,7 +1957,7 @@ bool hasNoDiamondSiblings(const RoseGraph &g, RoseVertex v) {
     assert(in_edges(v, g).first != in_edges(v, g).second);
 
     bool only_pred = true;
-    for (const auto &u : inv_adjacent_vertices_range(v, g)) {
+    for (const auto u : inv_adjacent_vertices_range(v, g)) {
         if (out_degree(u, g) > 1) {
             only_pred = false;
             break;
@@ -2066,7 +2066,7 @@ struct DupeLeafKey {
 struct UncalcLeafKey {
     UncalcLeafKey(const RoseGraph &g, RoseVertex v)
         : literals(g[v].literals), rose(g[v].left) {
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             RoseVertex u = source(e, g);
             preds.insert(make_pair(u, g[e]));
         }
@@ -2138,7 +2138,7 @@ void mergeDupeLeaves(RoseBuildImpl &build) {
                      g[t].index);
 
         vector<RoseEdge> deadEdges;
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             RoseVertex u = source(e, g);
             DEBUG_PRINTF("u index=%zu\n", g[u].index);
             if (RoseEdge et = edge(u, t, g)) {
diff --git a/src/rose/rose_in_dump.cpp b/src/rose/rose_in_dump.cpp
index 5266e9d7d..df93c8d47 100644
--- a/src/rose/rose_in_dump.cpp
+++ b/src/rose/rose_in_dump.cpp
@@ -99,7 +99,7 @@ void dumpPreRoseGraph(const RoseInGraph &ig, const Grey &grey,
 
     map<NGHolder *, size_t> graph_ids;
 
-    for (const auto &e : edges_range(ig)) {
+    for (const auto e : edges_range(ig)) {
         u32 u = i_map[source(e, ig)];
         u32 v = i_map[target(e, ig)];
         fprintf(f, "%u -> %u [label=\"", u, v);
diff --git a/src/rose/rose_in_util.cpp b/src/rose/rose_in_util.cpp
index 9fe47c276..93589b61e 100644
--- a/src/rose/rose_in_util.cpp
+++ b/src/rose/rose_in_util.cpp
@@ -98,7 +98,7 @@ unique_ptr<RoseInGraph> cloneRoseGraph(const RoseInGraph &ig) {
     unordered_map<const NGHolder *, shared_ptr<NGHolder>> graph_map;
     unordered_map<const raw_som_dfa *, shared_ptr<raw_som_dfa>> haig_map;
 
-    for (const auto &e : edges_range(ig)) {
+    for (const auto e : edges_range(ig)) {
         const RoseInEdgeProps &ep = ig[e];
         if (ep.graph && !contains(graph_map, ep.graph.get())) {
             graph_map[ep.graph.get()] = cloneHolder(*ep.graph);
@@ -133,7 +133,7 @@ void calcVertexOffsets(RoseInGraph &g) {
         u32 min_d = ROSE_BOUND_INF;
         u32 max_d = 0;
 
-        for (const auto &e : in_edges_range(v, g)) {
+        for (const auto e : in_edges_range(v, g)) {
             RoseInVertex u = source(e, g);
             u32 e_min = g[u].min_offset;
             u32 e_max = g[u].max_offset;
diff --git a/src/smallwrite/smallwrite_build.cpp b/src/smallwrite/smallwrite_build.cpp
index 4eb4801db..07995c5b6 100644
--- a/src/smallwrite/smallwrite_build.cpp
+++ b/src/smallwrite/smallwrite_build.cpp
@@ -329,7 +329,7 @@ void SmallWriteBuildImpl::add(const NGHolder &g, const ExpressionInfo &expr) {
 static
 bool add_to_trie(const ue2_literal &literal, ReportID report, LitTrie &trie) {
     auto u = trie.root;
-    for (const auto &c : literal) {
+    for (const auto c : literal) {
         auto next = LitTrie::null_vertex();
         for (auto v : adjacent_vertices_range(u, trie)) {
             if (trie[v].c == (u8)c.c) {
diff --git a/src/util/clique.cpp b/src/util/clique.cpp
index c2befea49..7ad1317e4 100644
--- a/src/util/clique.cpp
+++ b/src/util/clique.cpp
@@ -49,7 +49,7 @@ vector<u32> getNeighborInfo(const CliqueGraph &g,
     u32 id = g[cv].stateId;
     vector<u32> neighbor;
     // find neighbors for cv
-    for (const auto &v : adjacent_vertices_range(cv, g)) {
+    for (const auto v : adjacent_vertices_range(cv, g)) {
         if (g[v].stateId != id && contains(group, g[v].stateId)){
             neighbor.push_back(g[v].stateId);
             DEBUG_PRINTF("Neighbor:%u\n", g[v].stateId);
diff --git a/src/util/graph.h b/src/util/graph.h
index 3e18dae55..c7e381790 100644
--- a/src/util/graph.h
+++ b/src/util/graph.h
@@ -138,7 +138,7 @@ void find_unreachable(const Graph &g, const SourceCont &sources, OutCont *out) {
 
     find_reachable(g, sources, &reachable);
 
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (!contains(reachable, v)) {
             out->insert(v);
         }
@@ -186,7 +186,7 @@ bool has_parallel_edge(const Graph &g) {
     using vertex_descriptor = typename Graph::vertex_descriptor;
     ue2_unordered_set<std::pair<vertex_descriptor, vertex_descriptor>> seen;
 
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         auto u = source(e, g);
         auto v = target(e, g);
         if (!seen.emplace(u, v).second) {
@@ -304,7 +304,7 @@ template <class Graph>
 bool hasCorrectlyNumberedEdges(const Graph &g) {
     auto count = num_edges(g);
     std::vector<bool> ids(count, false);
-    for (const auto &e : edges_range(g)) {
+    for (const auto e : edges_range(g)) {
         auto id = g[e].index;
         if (id >= count || ids[id]) {
             return false; // duplicate
diff --git a/src/util/ue2_graph.h b/src/util/ue2_graph.h
index b8e2e935d..2fe9972d0 100644
--- a/src/util/ue2_graph.h
+++ b/src/util/ue2_graph.h
@@ -615,13 +615,13 @@ class ue2_graph : graph_detail::graph_base {
     std::pair<edge_descriptor, bool> edge_impl(vertex_descriptor u,
                                                vertex_descriptor v) const {
         if (in_degree_impl(v) < out_degree_impl(u)) {
-            for (const edge_descriptor &e : in_edges_range(v, *this)) {
+            for (const edge_descriptor e : in_edges_range(v, *this)) {
                 if (source_impl(e) == u) {
                     return {e, true};
                 }
             }
         } else {
-            for (const edge_descriptor &e : out_edges_range(u, *this)) {
+            for (const edge_descriptor e : out_edges_range(u, *this)) {
                 if (target_impl(e) == v) {
                     return {e, true};
                 }
diff --git a/src/util/ue2string.cpp b/src/util/ue2string.cpp
index 50b2bbcc8..a3eba3d9c 100644
--- a/src/util/ue2string.cpp
+++ b/src/util/ue2string.cpp
@@ -340,7 +340,7 @@ size_t ue2_literal::hash() const {
 void make_nocase(ue2_literal *lit) {
     ue2_literal rv;
 
-    for (const auto &elem: *lit) {
+    for (const auto elem: *lit) {
         rv.push_back(elem.c, ourisalpha(elem.c));
     }
 
diff --git a/unit/internal/graph_undirected.cpp b/unit/internal/graph_undirected.cpp
index 73d3e3570..736fc3254 100644
--- a/unit/internal/graph_undirected.cpp
+++ b/unit/internal/graph_undirected.cpp
@@ -56,7 +56,7 @@ using SimpleVertex = SimpleG::vertex_descriptor;
 template<typename Graph, typename Range>
 vector<size_t> to_indices(const Range &range, const Graph &g) {
     vector<size_t> indices;
-    for (const auto &elem : range) {
+    for (const auto elem : range) {
         indices.push_back(g[elem].index);
     }
     sort(indices.begin(), indices.end());
diff --git a/unit/internal/rose_build_merge.cpp b/unit/internal/rose_build_merge.cpp
index 5029f0a53..de206b4a7 100644
--- a/unit/internal/rose_build_merge.cpp
+++ b/unit/internal/rose_build_merge.cpp
@@ -85,7 +85,7 @@ static
 size_t numUniqueSuffixGraphs(const RoseGraph &g) {
     unordered_set<const NGHolder *> seen;
 
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (g[v].suffix) {
             assert(g[v].suffix.graph);
             seen.insert(g[v].suffix.graph.get());
diff --git a/util/ng_corpus_generator.cpp b/util/ng_corpus_generator.cpp
index e5e8e06cd..350fb2756 100644
--- a/util/ng_corpus_generator.cpp
+++ b/util/ng_corpus_generator.cpp
@@ -81,12 +81,12 @@ string pathToString(const NGHolder &g, const VertexPath &p) {
 /** True if this graph has no non-special successors of start or startDs. */
 static
 bool graph_is_empty(const NGHolder &g) {
-    for (const auto &v : adjacent_vertices_range(g.start, g)) {
+    for (const auto v : adjacent_vertices_range(g.start, g)) {
         if (!is_special(v, g)) {
             return false;
         }
     }
-    for (const auto &v : adjacent_vertices_range(g.start, g)) {
+    for (const auto v : adjacent_vertices_range(g.start, g)) {
         if (!is_special(v, g)) {
             return false;
         }
@@ -144,7 +144,7 @@ void findPaths(const NGHolder &g, CorpusProperties &cProps,
     open.push_back(ue2::make_unique<VertexPath>(1, g.start));
 
     unordered_set<NFAVertex> one_way_in;
-    for (const auto &v : vertices_range(g)) {
+    for (const auto v : vertices_range(g)) {
         if (in_degree(v, g) <= 1) {
             one_way_in.insert(v);
         }