Get command line options only if necessary

Rename `main` function according to argument count:

  * 0: `__main_void`
  * 2: `__main_argc_argv`

The entry point (`_start` function) calls `__main_void` function.
If user defines `main` as zero arguments, then it is called.
If user defines `main` as two arguments,
`__main_void` defined in library code is called
then user defined `main` function is called.

# Conflicts:
#	src/wcc/traverse.c

libsrc/_wasm/crt0/__main_void.c

@@ -0,0 +1,24 @@
+#include "alloca.h"
+
+#include "../wasi.h"
+
+extern int __main_argc_argv(int, char**);
+
+__attribute__((weak))
+int __main_void(void) {
+  char **argv;
+  int argc, len;
+  int r = args_sizes_get(&argc, &len);
+  if (r == 0) {
+    argv = alloca(sizeof(char*) * (argc + 1) + len);
+    char *str = ((char*)argv) + sizeof(char*) * (argc + 1);
+    args_get(argv, str);
+  } else {  // Ignore error.
+    argc = 1;
+    argv = alloca(sizeof(char*) * (argc + 1));
+    argv[0] = "*";
+  }
+  argv[argc] = NULL;
+
+  return __main_argc_argv(argc, argv);
+}

libsrc/_wasm/crt0/_start.c

@@ -1,30 +1,15 @@
-#include "alloca.h"  // alloca
 #include "stdlib.h"  // exit
 
 #include "../wasi.h"
 
 extern void __wasm_call_ctors(void);
 
 void _start(void) {
-#define main  __main_argc_argv
-  extern int main(int, char**);
-  char **argv;
-  int argc, len;
-  int r = args_sizes_get(&argc, &len);
-  if (r == 0) {
-    argv = alloca(sizeof(char*) * (argc + 1) + len);
-    char *str = ((char*)argv) + sizeof(char*) * (argc + 1);
-    args_get(argv, str);
-  } else {  // Ignore error.
-    argc = 1;
-    argv = alloca(sizeof(char*) * (argc + 1));
-    argv[0] = "*";
-  }
-  argv[argc] = NULL;
+  extern int __main_void(void);
 
   __wasm_call_ctors();
 
-  int ec = main(argc, argv);
+  int ec = __main_void();
   exit(ec);
 #undef main
 }

src/wcc/traverse.c

@@ -709,36 +709,23 @@ static void modify_func_name(Function *func) {
   const Name *newname = NULL;
   switch (func->params->len) {
   case 0:
-    {  // Add two parameters.
-      assert(func->scopes->len > 0);
-      Scope *scope = func->scopes->data[0];
-      const Name *name1 = alloc_label();
-      Type *type1 = &tyInt;
-      vec_push((Vector*)func->params, scope_add(scope, name1, type1, 0));
-      vec_push((Vector*)functype->func.params, type1);
-
-      Type *type2 = ptrof(ptrof(&tyChar));
-      const Name *name2 = alloc_label();
-      vec_push((Vector*)func->params, scope_add(scope, name2, type2, 0));
-      vec_push((Vector*)functype->func.params, type2);
-    }
-    // Fallthrough.
+    newname = alloc_name("__main_void", NULL, false);
+    break;
   case 2:
-    {
-      newname = alloc_name("__main_argc_argv", NULL, false);
-      VarInfo *vi = scope_find(global_scope, newname, NULL);
-      if (vi != NULL) {
-        const Token *token = func->body_block != NULL ? func->body_block->token : NULL;
-        parse_error(PE_NOFATAL, token, "`%.*s' function already defined", NAMES(newname));
-        return;
-      }
-    }
+    newname = alloc_name("__main_argc_argv", NULL, false);
     break;
   default:
     error("main function must take no argument or two arguments");
     break;
   }
 
+  VarInfo *vi = scope_find(global_scope, newname, NULL);
+  if (vi != NULL) {
+    const Token *token = func->body_block != NULL ? func->body_block->token : NULL;
+    parse_error(PE_NOFATAL, token, "`%.*s' function already defined", NAMES(newname));
+    return;
+  }
+
   // Rename two arguments `main` to `__main_argc_argv`.
   VarInfo *org_varinfo = scope_find(global_scope, main_name, NULL);
   assert(org_varinfo != NULL);