Adds a --help option and usage message listing all flags to V8.

Review URL: http://codereview.chromium.org/9420

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@702 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

samples/shell.cc

@@ -72,7 +72,7 @@ int main(int argc, char* argv[]) {
       // alone JavaScript engines.
       continue;
     } else if (strncmp(str, "--", 2) == 0) {
-      printf("Warning: unknown flag %s.\n", str);
+      printf("Warning: unknown flag %s.\nTry --help for options\n", str);
     } else if (strcmp(str, "-e") == 0 && i + 1 < argc) {
       // Execute argument given to -e option directly
       v8::HandleScope handle_scope;

src/d8.cc

@@ -318,6 +318,9 @@ void Shell::RunShell() {
 
 int Shell::Main(int argc, char* argv[]) {
   i::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
+  if (i::FLAG_help) {
+    return 1;
+  }
   Initialize();
   bool run_shell = (argc == 1);
   Context::Scope context_scope(evaluation_context_);

src/flag-definitions.h

@@ -200,6 +200,7 @@ DEFINE_string(testing_serialization_file, "/tmp/serdes",
 // Dev shell flags
 //
 
+DEFINE_bool(help, false, "Print usage message, including flags, on console")
 DEFINE_bool(dump_counters, false, "Dump counters on exit")
 
 //

src/flags.cc

@@ -317,7 +317,8 @@ int FlagList::SetFlagsFromCommandLine(int* argc,
           // sense there.
           continue;
         } else {
-          fprintf(stderr, "Error: unrecognized flag %s\n", arg);
+          fprintf(stderr, "Error: unrecognized flag %s\n"
+                  "Try --help for options\n", arg);
           return j;
         }
       }
@@ -327,7 +328,8 @@ int FlagList::SetFlagsFromCommandLine(int* argc,
         if (i < *argc) {
           value = argv[i++];
         } else {
-          fprintf(stderr, "Error: missing value for flag %s of type %s\n",
+          fprintf(stderr, "Error: missing value for flag %s of type %s\n"
+                  "Try --help for options\n",
                   arg, Type2String(flag->type()));
           return j;
         }
@@ -354,7 +356,8 @@ int FlagList::SetFlagsFromCommandLine(int* argc,
       if ((flag->type() == Flag::TYPE_BOOL && value != NULL) ||
           (flag->type() != Flag::TYPE_BOOL && is_bool) ||
           *endp != '\0') {
-        fprintf(stderr, "Error: illegal value for flag %s of type %s\n",
+        fprintf(stderr, "Error: illegal value for flag %s of type %s\n"
+                "Try --help for options\n",
                 arg, Type2String(flag->type()));
         return j;
       }
@@ -376,6 +379,9 @@ int FlagList::SetFlagsFromCommandLine(int* argc,
     *argc = j;
   }
 
+  if (FLAG_help) {
+    PrintHelp();
+  }
   // parsed all flags successfully
   return 0;
 }
@@ -447,10 +453,22 @@ void FlagList::ResetAllFlags() {
 
 // static
 void FlagList::PrintHelp() {
+  printf("Usage:\n");
+  printf("  shell [options] -e string\n");
+  printf("    execute string in V8\n");
+  printf("  shell [options] file1 file2 ... filek\n");
+  printf("    run JavaScript scripts in file1, file2, ..., filek\n");
+  printf("  shell [options]\n");
+  printf("  shell [options] --shell\n");
+  printf("    run an interactive JavaScript shell");
+  printf("  d8 [options] file\n");
+  printf("  d8 [options]\n");
+  printf("    run the new debugging shell\n\n");
+  printf("Options:\n");
   for (size_t i = 0; i < num_flags; ++i) {
     Flag* f = &flags[i];
     char* value = ToString(f);
-    printf("  --%s (%s)  type: %s  default: %s\n",
+    printf("  --%s (%s)\n        type: %s  default: %s\n",
            f->name(), f->comment(), Type2String(f->type()), value);
     DeleteArray(value);
   }

src/mksnapshot.cc

@@ -150,10 +150,10 @@ int main(int argc, char** argv) {
   // Print the usage if an error occurs when parsing the command line
   // flags or if the help flag is set.
   int result = i::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
-  if (result > 0 || argc != 2 || i::FLAG_h) {
+  if (result > 0 || argc != 2 || i::FLAG_help) {
     ::printf("Usage: %s [flag] ... outfile\n", argv[0]);
     i::FlagList::PrintHelp();
-    return !i::FLAG_h;
+    return !i::FLAG_help;
   }
 
   v8::V8::SetCounterFunction(counter_callback);