[WIP] Add better C support

include/cppast/compile_config.hpp

@@ -15,7 +15,7 @@
 
 namespace cppast
 {
-/// The C++ standard that should be used.
+/// The C/C++ standard that should be used.
 enum class cpp_standard
 {
     cpp_98,
@@ -26,8 +26,14 @@ enum class cpp_standard
     cpp_17,
     cpp_2a,
     cpp_20,
+    c_89,
+    c_99,
+    c_11,
+    c_17,
+    c_2x,
 
     cpp_latest = cpp_standard::cpp_14, //< The latest supported C++ standard.
+    c_latest = cpp_standard::c_17, //< The latest supported C standard.
 };
 
 /// \returns A human readable string representing the option,
@@ -52,12 +58,82 @@ inline const char* to_string(cpp_standard standard) noexcept
         return "c++2a";
     case cpp_standard::cpp_20:
         return "c++20";
+    case cpp_standard::c_89:
+        return "c89";
+    case cpp_standard::c_99:
+        return "c99";
+    case cpp_standard::c_11:
+        return "c11";
+    case cpp_standard::c_17:
+        return "c17";
+    case cpp_standard::c_2x:
+        return "c2x";
     }
 
     DEBUG_UNREACHABLE(detail::assert_handler{});
     return "ups";
 }
 
+/// \returns The C/C++ standard corresponding to the string, e.g. `cpp_14` for `c++14`
+/// \throws std::invalid_argument for an unknown language standard
+inline cpp_standard to_standard(const std::string& str)
+{
+    if (str == "c++98")
+        return cpp_standard::cpp_98;
+    else if (str == "c++03")
+        return cpp_standard::cpp_03;
+    else if (str == "c++11")
+        return cpp_standard::cpp_11;
+    else if (str == "c++14")
+        return cpp_standard::cpp_14;
+    else if (str == "c++1z")
+        return cpp_standard::cpp_1z;
+    else if (str == "c++17")
+        return cpp_standard::cpp_17;
+    else if (str == "c++2a")
+        return cpp_standard::cpp_2a;
+    else if (str == "c++20")
+        return cpp_standard::cpp_20;
+    else if (str == "c89")
+        return cpp_standard::c_89;
+    else if (str == "c99")
+        return cpp_standard::c_99;
+    else if (str == "c11")
+        return cpp_standard::c_11;
+    else if (str == "c17")
+        return cpp_standard::c_17;
+    else if (str == "c2x")
+        return cpp_standard::c_2x;
+    else
+        throw std::invalid_argument("invalid C/C++ standard '" + str + "'");
+}
+
+/// \returns whether the language standard is a C standard
+inline bool is_c_standard(cpp_standard standard) noexcept
+{
+    switch (standard)
+    {
+    case cpp_standard::cpp_98:
+    case cpp_standard::cpp_03:
+    case cpp_standard::cpp_11:
+    case cpp_standard::cpp_14:
+    case cpp_standard::cpp_1z:
+    case cpp_standard::cpp_17:
+    case cpp_standard::cpp_2a:
+    case cpp_standard::cpp_20:
+        return false;
+    case cpp_standard::c_89:
+    case cpp_standard::c_99:
+    case cpp_standard::c_11:
+    case cpp_standard::c_17:
+    case cpp_standard::c_2x:
+        return true;
+    }
+
+    DEBUG_UNREACHABLE(detail::assert_handler{});
+    return false;
+}
+
 /// Other special compilation flags.
 enum class compile_flag
 {
@@ -114,6 +190,12 @@ class compile_config
         return do_get_name();
     }
 
+    /// \returns Whether to parse files as C rather than C++.
+    bool use_c() const noexcept
+    {
+        return do_use_c();
+    }
+
 protected:
     compile_config(std::vector<std::string> def_flags) : flags_(std::move(def_flags)) {}
 
@@ -157,6 +239,9 @@ class compile_config
     /// \notes This allows detecting mismatches of configurations and parsers.
     virtual const char* do_get_name() const noexcept = 0;
 
+    /// \returns Whether to parse files as C rather than C++.
+    virtual bool do_use_c() const noexcept = 0;
+
     std::vector<std::string> flags_;
 };
 } // namespace cppast

include/cppast/cpp_storage_class_specifiers.hpp

@@ -19,10 +19,16 @@ enum cpp_storage_class_specifiers : int
 
     cpp_storage_class_auto = 1, //< *automatic* storage duration.
 
-    cpp_storage_class_static = 2, //< *static* or *thread* storage duration and *internal* linkage.
-    cpp_storage_class_extern = 4, //< *static* or *thread* storage duration and *external* linkage.
 
-    cpp_storage_class_thread_local = 8, //< *thread* storage duration.
+    cpp_storage_class_register = 2, //< *automatic* storage duration.
+    /// Hints to the compiler to keep this in a register.
+    /// \notes In C a register variable cannot have its address taken. For C++ `register` is
+    /// deprecated in C++11 and removed in C++17.
+
+    cpp_storage_class_static = 4, //< *static* or *thread* storage duration and *internal* linkage.
+    cpp_storage_class_extern = 8, //< *static* or *thread* storage duration and *external* linkage.
+
+    cpp_storage_class_thread_local = 16, //< *thread* storage duration.
     /// \notes This is the only one that can be combined with the others.
 };
 
@@ -49,6 +55,13 @@ inline bool is_extern(cpp_storage_class_specifiers spec) noexcept
 {
     return (spec & cpp_storage_class_extern) != 0;
 }
+
+/// \returns Whether the [cppast::cpp_storage_class_specifiers]() contain `register`.
+inline bool is_register(cpp_storage_class_specifiers spec) noexcept
+{
+    return (spec & cpp_storage_class_register) != 0;
+}
 } // namespace cppast
 
+
 #endif // CPPAST_CPP_STORAGE_CLASS_SPECIFIERS_HPP_INCLUDED

include/cppast/cpp_type.hpp

@@ -286,25 +286,47 @@ class cpp_dependent_type final : public cpp_type
     std::unique_ptr<cpp_type> dependee_;
 };
 
-/// The kinds of C++ cv qualifiers.
-enum cpp_cv : int
+/// Flags for the kinds of C/C++ qualifiers.
+enum cpp_cv_flags : int
 {
-    cpp_cv_none,
-    cpp_cv_const,
-    cpp_cv_volatile,
-    cpp_cv_const_volatile,
+    cpp_cv_const, //< constant type
+    cpp_cv_volatile, //< volatile type
+    cpp_cv_restrict, //< restrict pointer type (C-only)
+    cpp_cv_atomic, //< atomic type (C-only)
+
+    _flag_set_size, //< \exclude
 };
 
+/// Flag set for the kinds for C/C++ qualifiers.
+using cpp_cv = type_safe::flag_set<cpp_cv_flags>;
+
+/// Represents a const volatile qualified type
+constexpr cpp_cv cpp_cv_const_volatile = cpp_cv(cpp_cv_const) | cpp_cv_volatile;
+/// Represents an unqualified type
+constexpr cpp_cv cpp_cv_none = cpp_cv();
+
 /// \returns `true` if the qualifier contains `const`.
-inline bool is_const(cpp_cv cv) noexcept
+inline bool is_const(const cpp_cv& cv) noexcept
 {
-    return cv == cpp_cv_const || cv == cpp_cv_const_volatile;
+    return (cv & cpp_cv_const) != 0;
 }
 
 /// \returns `true` if the qualifier contains `volatile`.
-inline bool is_volatile(cpp_cv cv) noexcept
+inline bool is_volatile(const cpp_cv& cv) noexcept
+{
+    return (cv & cpp_cv_volatile) != 0;
+}
+
+/// \returns `true` if the qualifier contains `restrict`.
+inline bool is_restrict(const cpp_cv& cv) noexcept
 {
-    return cv == cpp_cv_volatile || cv == cpp_cv_const_volatile;
+    return (cv & cpp_cv_restrict) != 0;
+}
+
+/// \returns `true` if the qualifier contains `atomic`.
+inline bool is_atomic(const cpp_cv& cv) noexcept
+{
+    return (cv & cpp_cv_atomic) != 0;
 }
 
 /// A [cppast::cpp_cv]() qualified [cppast::cpp_type]().
@@ -355,6 +377,12 @@ const cpp_type& remove_const(const cpp_type& type) noexcept;
 /// \returns The type without top-level volatile qualifiers.
 const cpp_type& remove_volatile(const cpp_type& type) noexcept;
 
+/// \returns The type without top-level restrict qualifiers.
+const cpp_type& remove_restrict(const cpp_type& type) noexcept;
+
+/// \returns The type without top-level atomic qualifiers.
+const cpp_type& remove_atomic(const cpp_type& type) noexcept;
+
 /// A pointer to a [cppast::cpp_type]().
 class cpp_pointer_type final : public cpp_type
 {

include/cppast/cpp_type_alias.hpp

@@ -18,26 +18,35 @@ class cpp_type_alias final : public cpp_entity
 
     /// \returns A newly created and registered type alias.
     static std::unique_ptr<cpp_type_alias> build(const cpp_entity_index& idx, cpp_entity_id id,
-                                                 std::string name, std::unique_ptr<cpp_type> type);
+                                                 std::string name, std::unique_ptr<cpp_type> type,
+                                                 bool use_c_style = false);
 
     /// \returns A newly created type alias that isn't registered.
     /// \notes This function is intendend for templated type aliases.
-    static std::unique_ptr<cpp_type_alias> build(std::string name, std::unique_ptr<cpp_type> type);
+    static std::unique_ptr<cpp_type_alias> build(std::string name, std::unique_ptr<cpp_type> type,
+                                                 bool use_c_style = false);
 
     /// \returns A reference to the aliased [cppast::cpp_type]().
     const cpp_type& underlying_type() const noexcept
     {
         return *type_;
     }
 
+    /// \returns Whether to generate C-style typedefs instead of C++ using statements
+    bool use_c_style() const noexcept
+    {
+        return use_c_style_;
+    }
+
 private:
-    cpp_type_alias(std::string name, std::unique_ptr<cpp_type> type)
-    : cpp_entity(std::move(name)), type_(std::move(type))
+    cpp_type_alias(std::string name, std::unique_ptr<cpp_type> type, bool use_c_style)
+    : cpp_entity(std::move(name)), type_(std::move(type)), use_c_style_(use_c_style)
     {}
 
     cpp_entity_kind do_get_entity_kind() const noexcept override;
 
     std::unique_ptr<cpp_type> type_;
+    bool                      use_c_style_;
 };
 } // namespace cppast
 

include/cppast/cppast_fwd.hpp

@@ -102,7 +102,7 @@ enum class visit_filter;
 
 enum cpp_access_specifier_kind : int;
 enum cpp_builtin_type_kind : int;
-enum cpp_cv : int;
+enum cpp_cv_flags : int;
 enum cpp_function_body_kind : int;
 enum cpp_reference : int;
 enum cpp_storage_class_specifiers : int;

include/cppast/libclang_parser.hpp

@@ -166,10 +166,13 @@ class libclang_compile_config final : public compile_config
         return "libclang";
     }
 
+    bool do_use_c() const noexcept override;
+
     std::string clang_binary_;
     bool        write_preprocessed_ : 1;
     bool        fast_preprocessing_ : 1;
     bool        remove_comments_in_macro_ : 1;
+    bool        use_c_     : 1;
 
     friend detail::libclang_compile_config_access;
 };

src/code_generator.cpp

@@ -1,6 +1,7 @@
 // Copyright (C) 2017-2022 Jonathan Müller and cppast contributors
 // SPDX-License-Identifier: MIT
 
+#include "cppast/cpp_type.hpp"
 #include <cppast/code_generator.hpp>
 
 #include <cppast/cpp_alias_template.hpp>
@@ -241,13 +242,25 @@ bool generate_type_alias(code_generator& generator, const cpp_type_alias& alias,
     code_generator::output output(type_safe::ref(generator), type_safe::ref(alias), cur_access);
     if (output)
     {
-        output << keyword("using") << whitespace << identifier(alias.name()) << operator_ws
-               << punctuation("=") << operator_ws;
-        if (output.options() & code_generator::exclude_target)
-            output.excluded(alias);
+        if (alias.use_c_style())
+        {
+            output << keyword("typedef") << whitespace;
+            if (output.options() & code_generator::exclude_target)
+                output.excluded(alias);
+            else
+                detail::write_type(output, alias.underlying_type(), "");
+            output << whitespace << identifier(alias.name()) << punctuation(";") << newl;
+        }
         else
-            detail::write_type(output, alias.underlying_type(), "");
-        output << punctuation(";") << newl;
+        {
+            output << keyword("using") << whitespace << identifier(alias.name()) << operator_ws
+                << punctuation("=") << operator_ws;
+            if (output.options() & code_generator::exclude_target)
+                output.excluded(alias);
+            else
+                detail::write_type(output, alias.underlying_type(), "");
+            output << punctuation(";") << newl;
+        }
     }
     return static_cast<bool>(output);
 }
@@ -471,6 +484,8 @@ void write_storage_class(code_generator::output& output, cpp_storage_class_speci
         output << keyword("extern") << whitespace;
     if (is_thread_local(storage))
         output << keyword("thread_local") << whitespace;
+    if (is_register(storage))
+        output << keyword("register") << whitespace;
     if (is_constexpr)
         output << keyword("constexpr") << whitespace;
     else if (is_consteval)
@@ -658,22 +673,28 @@ void write_suffix_virtual(code_generator::output& output, const cpp_virtual& vir
 bool write_cv_ref(code_generator::output& output, const cpp_member_function_base& base)
 {
     auto need_ws = false;
-    switch (base.cv_qualifier())
+    auto cv = base.cv_qualifier();
+
+    std::vector<const char*> qualifiers;
+    if (is_const(cv))
+        qualifiers.push_back("const");
+    if (is_volatile(cv))
+        qualifiers.push_back("volatile");
+    if (is_atomic(cv))
+        qualifiers.push_back("_Atomic");
+    if (is_restrict(cv))
+        qualifiers.push_back("restrict");
+
+    bool first = true;
+    for (auto& q : qualifiers)
     {
-    case cpp_cv_none:
-        break;
-    case cpp_cv_const:
-        output << operator_ws << keyword("const");
-        need_ws = true;
-        break;
-    case cpp_cv_volatile:
-        output << operator_ws << keyword("volatile");
-        need_ws = true;
-        break;
-    case cpp_cv_const_volatile:
-        output << operator_ws << keyword("const") << whitespace << keyword("volatile");
+        if (first)
+            output << operator_ws;
+        else
+            output << whitespace;
+        output << keyword(std::move(q));
+        first = false;
         need_ws = true;
-        break;
     }
 
     switch (base.ref_qualifier())