Fix warnings with g++-11 compilation

CMakeLists.txt

@@ -166,7 +166,10 @@ endif()
 
 # Compiler flags
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU")
-  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -Wstrict-prototypes -fvisibility=hidden)
+  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden)
+  if(NOT MI_USE_CXX)
+    list(APPEND mi_cflags -Wstrict-prototypes)
+  endif()
   if(CMAKE_C_COMPILER_ID MATCHES "GNU")
     list(APPEND mi_cflags -Wno-invalid-memory-model)
   endif()

src/arena.c

@@ -310,7 +310,7 @@ bool mi_manage_os_memory(void* start, size_t size, bool is_committed, bool is_la
   // the bitmaps are already zero initialized due to os_alloc
   // initialize committed bitmap?
   if (arena->blocks_committed != NULL && is_committed) {
-    memset(arena->blocks_committed, 0xFF, fields*sizeof(mi_bitmap_field_t));
+    memset((void*)arena->blocks_committed, 0xFF, fields*sizeof(mi_bitmap_field_t)); // cast to void* to avoid atomic warning
   }
   // and claim leftover blocks if needed (so we never allocate there)
   ptrdiff_t post = (fields * MI_BITMAP_FIELD_BITS) - bcount;

src/region.c

@@ -463,7 +463,7 @@ void _mi_mem_collect(mi_os_tld_t* tld) {
         uint8_t* start = (uint8_t*)mi_atomic_load_ptr_acquire(uint8_t,&regions[i].start);
         size_t arena_memid = mi_atomic_load_relaxed(&regions[i].arena_memid);
         uintptr_t commit = mi_atomic_load_relaxed(&regions[i].commit);
-        memset(&regions[i], 0, sizeof(mem_region_t));
+        memset((void*)&regions[i], 0, sizeof(mem_region_t));  // cast to void* to avoid atomic warning
         // and release the whole region
         mi_atomic_store_release(&region->info, (uintptr_t)0);
         if (start != NULL) { // && !_mi_os_is_huge_reserved(start)) {