Add -Wextra compiler flag

SConstruct

@@ -41,7 +41,7 @@ test_lib_includes = ["third-party/unity/src/"]
 VariantDir(variant_dir, ".", duplicate=0)
 # Minimization flags for later:
 # CCFLAGS = ["-Oz", "-flto", "-ffunction-sections", "-fdata-sections", "-Wl,--gc-sections", "-lreadline"]
-CCFLAGS = ["-ggdb", "-O0", "-Werror", "-Wall"]
+CCFLAGS = ["-ggdb", "-O0", "-Werror", "-Wall", "-Wextra", "-Wno-unused-parameter"]
 env = Environment(
     CPPPATH=lib_includes, COMPILATIONDB_USE_ABSPATH=True, CCFLAGS=CCFLAGS
 )

src/arena.c

@@ -36,7 +36,7 @@ struct ucl_arena *ucl_arena_create(size_t object_size, size_t capacity) {
 void ucl_arena_map(struct ucl_arena *arena, void (*map_function)(struct ucl_arena * arena, void *object)) {
     size_t used_map_ints = DIV_ROUND_UP(arena->capacity, INT_BITS);
 
-    for (int i = 0; i < used_map_ints; i++ ) {
+    for (unsigned int i = 0; i < used_map_ints; i++ ) {
         // TODO: Allow for 'put' in map
         int map = arena->used_map[i];
         while (map) {
@@ -60,8 +60,8 @@ void *ucl_arena_get(struct ucl_arena *arena) {
             continue;
         }
 
-        int bit_index = __builtin_ffs(~map) - 1;
-        int index = bit_index + INT_BITS * i;
+        unsigned int bit_index = __builtin_ffs(~map) - 1;
+        unsigned int index = bit_index + INT_BITS * i;
         if (index >= arena->capacity) {
             // This might happen in the last used_map_int when (capacity % int_bits != 0)
             return NULL;
@@ -88,7 +88,6 @@ void ucl_arena_put(struct ucl_arena *arena, void *object) {
     unsigned int bit_index = index % INT_BITS;
 
     assert(offset % arena->object_size == 0);
-    assert(index >= 0);
     assert(index < arena->capacity);
 
     assert(arena->used_map[int_index] & (1 << bit_index));

src/parse.c

@@ -127,7 +127,7 @@ struct ucl_object *ucl_parse_token_atom(struct ucl_object *maybe_atom) {
             break;
         case UCL_TYPE_SYMBOL: {
             // Check for reserved tokens first, which indicate special, non-atom behavior
-            for (int i = 0; i < ARRAY_SIZE(reserved_symbols); i++) {
+            for (unsigned int i = 0; i < ARRAY_SIZE(reserved_symbols); i++) {
                 if (!strcmp(maybe_atom->string, reserved_symbols[i])) {
                     return NULL;
                 }