[debugserver] Add --version/-V command line option to debugserver.

[JDevlieghere]

Summary

When not running under a TTY the output is buffered and not flushed
before debugserver exits which makes it impossible to parse the version
string. This adds a -V/--version command that just prints the version
to stdout and exits with an exit code zero.

[jasonmolenda]

Hm, if the goal is to get -version (an unrecognized cmd line option) to explicitly print to stderr, don't we want to change the lines in show_usage_and_exit? I think this change would result in us not getting the version string in console logs for normal debug sessions, where we want to keep it.

[jasonmolenda]

Awesome.

[aprantl]

Good catch!

lldb/trunk/tools/debugserver/source/debugserver.cpp

void FileLogCallback(void *baton, uint32_t flags, const char *format,
   if (baton == NULL || format == NULL)
     return;
 
   ::vfprintf((FILE *)baton, format, args);
   ::fprintf((FILE *)baton, "\n");
   ::fflush((FILE *)baton);
 }
 
+void show_version_and_exit(int exit_code) {
+  printf("%s-%s for %s.\n", DEBUGSERVER_PROGRAM_NAME, DEBUGSERVER_VERSION_STR,
+         RNB_ARCH);
+  exit(exit_code);
+}
+
 void show_usage_and_exit(int exit_code) {
   RNBLogSTDERR(
       "Usage:\n  %s host:port [program-name program-arg1 program-arg2 ...]\n",
       DEBUGSERVER_PROGRAM_NAME);
   RNBLogSTDERR("  %s /path/file [program-name program-arg1 program-arg2 ...]\n",
                DEBUGSERVER_PROGRAM_NAME);
   RNBLogSTDERR("  %s host:port --attach=<pid>\n", DEBUGSERVER_PROGRAM_NAME);
   RNBLogSTDERR("  %s /path/file --attach=<pid>\n", DEBUGSERVER_PROGRAM_NAME);
   RNBLogSTDERR("  %s host:port --attach=<process_name>\n",
                DEBUGSERVER_PROGRAM_NAME);
   RNBLogSTDERR("  %s /path/file --attach=<process_name>\n",
                DEBUGSERVER_PROGRAM_NAME);
   exit(exit_code);
 }
 
 // option descriptors for getopt_long_only()
 static struct option g_long_options[] = {
     {"attach", required_argument, NULL, 'a'},
     {"arch", required_argument, NULL, 'A'},
     {"debug", no_argument, NULL, 'g'},
     {"kill-on-error", no_argument, NULL, 'K'},
     {"verbose", no_argument, NULL, 'v'},
+    {"version", no_argument, NULL, 'V'},
     {"lockdown", no_argument, &g_lockdown_opt, 1}, // short option "-k"
     {"applist", no_argument, &g_applist_opt, 1},   // short option "-t"
     {"log-file", required_argument, NULL, 'l'},
     {"log-flags", required_argument, NULL, 'f'},
     {"launch", required_argument, NULL, 'x'}, // Valid values are "auto",
                                               // "posix-spawn", "fork-exec",
                                               // "springboard" (arm only)
     {"waitfor", required_argument, NULL,
#endif
 
     case 'R':
       reverse_connect = true;
       break;
     case 'v':
       DNBLogSetVerbose(1);
       break;
 
+    case 'V':
+      show_version_and_exit(0);
+      break;
+
     case 's':
       ctx.GetSTDIN().assign(optarg);
       ctx.GetSTDOUT().assign(optarg);
       ctx.GetSTDERR().assign(optarg);
       break;
 
     case 'I':
       ctx.GetSTDIN().assign(optarg);