Add predefine macros such as __STDC__

preprocess.c

@@ -783,8 +783,59 @@ static Token *preprocess2(Token *tok) {
   return head.next;
 }
 
+static void define_macro(char *name, char *buf) {
+  Token *tok = tokenize(new_file("<built-in>", 1, buf));
+  add_macro(name, true, tok);
+}
+
+static void init_macros(void) {
+  // Define predefined macros
+  define_macro("_LP64", "1");
+  define_macro("__C99_MACRO_WITH_VA_ARGS", "1");
+  define_macro("__ELF__", "1");
+  define_macro("__LP64__", "1");
+  define_macro("__SIZEOF_DOUBLE__", "8");
+  define_macro("__SIZEOF_FLOAT__", "4");
+  define_macro("__SIZEOF_INT__", "4");
+  define_macro("__SIZEOF_LONG_DOUBLE__", "8");
+  define_macro("__SIZEOF_LONG_LONG__", "8");
+  define_macro("__SIZEOF_LONG__", "8");
+  define_macro("__SIZEOF_POINTER__", "8");
+  define_macro("__SIZEOF_PTRDIFF_T__", "8");
+  define_macro("__SIZEOF_SHORT__", "2");
+  define_macro("__SIZEOF_SIZE_T__", "8");
+  define_macro("__SIZE_TYPE__", "unsigned long");
+  define_macro("__STDC_HOSTED__", "1");
+  define_macro("__STDC_NO_ATOMICS__", "1");
+  define_macro("__STDC_NO_COMPLEX__", "1");
+  define_macro("__STDC_NO_THREADS__", "1");
+  define_macro("__STDC_NO_VLA__", "1");
+  define_macro("__STDC_VERSION__", "201112L");
+  define_macro("__STDC__", "1");
+  define_macro("__USER_LABEL_PREFIX__", "");
+  define_macro("__alignof__", "_Alignof");
+  define_macro("__amd64", "1");
+  define_macro("__amd64__", "1");
+  define_macro("__chibicc__", "1");
+  define_macro("__const__", "const");
+  define_macro("__gnu_linux__", "1");
+  define_macro("__inline__", "inline");
+  define_macro("__linux", "1");
+  define_macro("__linux__", "1");
+  define_macro("__signed__", "signed");
+  define_macro("__typeof__", "typeof");
+  define_macro("__unix", "1");
+  define_macro("__unix__", "1");
+  define_macro("__volatile__", "volatile");
+  define_macro("__x86_64", "1");
+  define_macro("__x86_64__", "1");
+  define_macro("linux", "1");
+  define_macro("unix", "1");
+}
+
 // Entry point function of the preprocessor.
 Token *preprocess(Token *tok) {
+  init_macros();
   tok = preprocess2(tok);
   if (cond_incl)
     error_tok(cond_incl->tok, "unterminated conditional directive");

test/macro.c

@@ -322,6 +322,8 @@ int main() {
 
 #undef foo
 
+  ASSERT(1, __STDC__);
+
   printf("OK\n");
   return 0;
 }