Add -std=c11 option which sets __STDC_VERSION__ to 201112L and allows to implement c11 features conditionally

libtcc.c

@@ -733,6 +733,7 @@ LIBTCCAPI TCCState *tcc_new(void)
     ++nb_states;
 
     s->nocommon = 1;
+    s->cversion = 199901; /* default unless -std=c11 is supplied */
     s->warn_implicit_function_declaration = 1;
     s->ms_extensions = 1;
 
@@ -1790,8 +1791,16 @@ reparse:
             s->static_link = 1;
             break;
         case TCC_OPTION_std:
-    	    /* silently ignore, a current purpose:
-    	       allow to use a tcc as a reference compiler for "make test" */
+            if (*optarg == '=') {
+                ++optarg;
+                if (strcmp(optarg, "c11") == 0) {
+                   tcc_undefine_symbol(s, "__STDC_VERSION__");
+                   tcc_define_symbol(s, "__STDC_VERSION__", "201112L");
+                   s->cversion = 201112;
+                }
+            }
+    	      /* silently ignore other values, a current purpose:
+    	         allow to use a tcc as a reference compiler for "make test" */
             break;
         case TCC_OPTION_shared:
             x = TCC_OUTPUT_DLL;

tcc.c

@@ -33,6 +33,8 @@ static const char help[] =
     "  -o outfile  set output filename\n"
     "  -run        run compiled source\n"
     "  -fflag      set or reset (with 'no-' prefix) 'flag' (see tcc -hh)\n"
+    "  -std=c99    Conform to the ISO 1999 C standard (default).\n"
+    "  -std=c11    Conform to the ISO 2011 C standard.\n"
     "  -Wwarning   set or reset (with 'no-' prefix) 'warning' (see tcc -hh)\n"
     "  -w          disable all warnings\n"
     "  -v -vv      show version, show search paths or loaded files\n"

tcc.h

@@ -651,6 +651,7 @@ struct TCCState {
     int rdynamic; /* if true, all symbols are exported */
     int symbolic; /* if true, resolve symbols in the current module first */
     int filetype; /* file type for compilation (NONE,C,ASM) */
+    int cversion; /* supported C ISO version, 199901 (the default), 201112, ... */
 
     char *tcc_lib_path; /* CONFIG_TCCDIR or -B option */
     char *soname; /* as specified on the command line (-soname) */