Fix compiler warnings

Makefile

@@ -1,7 +1,9 @@
 DOCS_DIR := docs
+# Default compiler flags (override with: make CFLAGS="...").
+CFLAGS ?= -Wall -Wextra -Wsign-compare -Werror
 
 build:
-	luarocks --local make
+	CFLAGS="$(CFLAGS)" luarocks --local make
 
 spec: test
 

src/luaharfbuzz/buffer.c

@@ -143,7 +143,7 @@ static int buffer_add_codepoints(lua_State *L) {
   item_offset = luaL_optinteger(L, 3, 0);
   item_length = luaL_optinteger(L, 4, -1);
 
-  int n = lua_rawlen(L, 2);
+  unsigned int n = lua_rawlen(L, 2);
 
   hb_codepoint_t *text = (hb_codepoint_t *) malloc(n * sizeof(hb_codepoint_t));
 

src/luaharfbuzz/face.c

@@ -492,7 +492,7 @@ static int face_var_get_axis_infos(lua_State *L) {
     hb_ot_var_get_axis_infos(*face, start, &count, axis_infos);
 
     lua_createtable(L, count, 0);
-    for (int i = 0; i != count; i++) {
+    for (unsigned int i = 0; i != count; i++) {
       push_axis_info(L, axis_infos + i);
       lua_seti(L, -2, i + 1);
     }
@@ -549,7 +549,7 @@ static int face_var_named_instance_get_design_coords(lua_State *L) {
   unsigned int count = STATIC_ARRAY_SIZE;
   count = hb_ot_var_named_instance_get_design_coords(*face, index, &count, coords);
 
-  for (int i = 0; i != count; i++) {
+  for (unsigned int i = 0; i != count; i++) {
     lua_pushnumber(L, coords[i]);
   }
   return count;
@@ -570,7 +570,7 @@ static int face_var_normalize_variations(lua_State *L) {
   int normalized[STATIC_ARRAY_SIZE];
   hb_ot_var_normalize_variations(*face, variations, count, normalized, coord_count);
 
-  for (int i = 0; i != coord_count; i++) {
+  for (unsigned int i = 0; i != coord_count; i++) {
     lua_pushinteger(L, normalized[i]);
   }
   return coord_count;
@@ -590,7 +590,7 @@ static int face_var_normalize_coords(lua_State *L) {
   int normalized[STATIC_ARRAY_SIZE];
   hb_ot_var_normalize_coords(*face, count, coords, normalized);
 
-  for (int i = 0; i != count; i++) {
+  for (unsigned int i = 0; i != count; i++) {
     lua_pushinteger(L, normalized[i]);
   }
   return count;

src/luaharfbuzz/font.c

@@ -249,7 +249,7 @@ static int font_set_variations(lua_State *L) {
   if (count > 128)
     count = 128;
   Variation variations[128];
-  for (int i = 0; i != count; i++)
+  for (unsigned int i = 0; i != count; i++)
     variations[i] = *(Variation *)luaL_checkudata(L, i + 2, "harfbuzz.Variation");
 
   hb_font_set_variations(*f, variations, count);
@@ -262,7 +262,7 @@ static int font_set_var_coords_design(lua_State *L) {
   if (count > 128)
     count = 128;
   float coords[128];
-  for (int i = 0; i != count; i++)
+  for (unsigned int i = 0; i != count; i++)
     coords[i] = luaL_checknumber(L, i + 2);
 
   hb_font_set_var_coords_design(*f, coords, count);
@@ -275,7 +275,7 @@ static int font_set_var_coords_normalized(lua_State *L) {
   if (count > 128)
     count = 128;
   int coords[128];
-  for (int i = 0; i != count; i++)
+  for (unsigned int i = 0; i != count; i++)
     coords[i] = luaL_checkinteger(L, i + 2);
 
   hb_font_set_var_coords_normalized(*f, coords, count);
@@ -294,7 +294,7 @@ static int font_get_var_coords_normalized(lua_State *L) {
   Font *f = (Font *)luaL_checkudata(L, 1, "harfbuzz.Font");
   unsigned int count;
   const int *coords = hb_font_get_var_coords_normalized(*f, &count);
-  for (int i = 0; i != count; i++)
+  for (unsigned int i = 0; i != count; i++)
     lua_pushinteger(L, coords[i]);
   return count;
 }