Make void* arithmetic fail the build for debug builds

Author: bmatherly

CMakeLists.txt

@@ -149,7 +149,7 @@ endif()
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_BUILD_TYPE STREQUAL "Debug")
   # Treat warnings as errors with some exceptions
-  set(GCC_FLAGS "-Wall -Werror -Wno-deprecated-declarations")
+  set(GCC_FLAGS "-Wall -Werror -Wno-deprecated-declarations -Werror=pointer-arith")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_FLAGS} -Wno-class-memaccess -Wno-array-compare -Wno-unused-result -Wno-maybe-uninitialized")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_FLAGS} -Wno-discarded-qualifiers")
   # The following showed up in GCC 14, which I am using via msys2 on Windows.