generator: Acquire lock to prevent two parallel runs of the generator.

[libguestfs.git] / src / generator.ml

diff --git a/src/generator.ml b/src/generator.ml
old mode 100644 (file)
new mode 100755 (executable)
index 2317541..e3584cc
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -5398,20 +5398,20 @@ check_state (guestfs_h *g, const char *caller)
            pr "  /* caller will free this */\n";
            pr "  return safe_memdup (g, &ret.%s, sizeof (ret.%s));\n" n n
        | RBufferOut n ->
-          pr "  /* RBufferOut is tricky: If the buffer is zero-length, then\n";
-          pr "   * _val might be NULL here.  To make the API saner for\n";
-          pr "   * callers, we turn this case into a unique pointer (using\n";
-          pr "   * malloc(1)).\n";
-          pr "   */\n";
-          pr "  if (ret.%s.%s_len > 0) {\n" n n;
+           pr "  /* RBufferOut is tricky: If the buffer is zero-length, then\n";
+           pr "   * _val might be NULL here.  To make the API saner for\n";
+           pr "   * callers, we turn this case into a unique pointer (using\n";
+           pr "   * malloc(1)).\n";
+           pr "   */\n";
+           pr "  if (ret.%s.%s_len > 0) {\n" n n;
            pr "    *size_r = ret.%s.%s_len;\n" n n;
            pr "    return ret.%s.%s_val; /* caller will free */\n" n n;
-          pr "  } else {\n";
-          pr "    free (ret.%s.%s_val);\n" n n;
-          pr "    char *p = safe_malloc (g, 1);\n";
+           pr "  } else {\n";
+           pr "    free (ret.%s.%s_val);\n" n n;
+           pr "    char *p = safe_malloc (g, 1);\n";
            pr "    *size_r = ret.%s.%s_len;\n" n n;
            pr "    return p;\n";
-          pr "  }\n";
+           pr "  }\n";
       );
 
       pr "}\n\n"
@@ -5592,18 +5592,18 @@ and generate_daemon_actions () =
        | RConstString _ | RConstOptString _
        | RString _ | RStringList _ | RHashtable _
        | RStruct (_, _) | RStructList (_, _) ->
-          pr "  if (r == %s)\n" error_code;
-          pr "    /* do_%s has already called reply_with_error */\n" name;
-          pr "    goto done;\n";
-          pr "\n"
+           pr "  if (r == %s)\n" error_code;
+           pr "    /* do_%s has already called reply_with_error */\n" name;
+           pr "    goto done;\n";
+           pr "\n"
        | RBufferOut _ ->
-          pr "  /* size == 0 && r == NULL could be a non-error case (just\n";
-          pr "   * an ordinary zero-length buffer), so be careful ...\n";
-          pr "   */\n";
-          pr "  if (size == 1 && r == %s)\n" error_code;
-          pr "    /* do_%s has already called reply_with_error */\n" name;
-          pr "    goto done;\n";
-          pr "\n"
+           pr "  /* size == 0 && r == NULL could be a non-error case (just\n";
+           pr "   * an ordinary zero-length buffer), so be careful ...\n";
+           pr "   */\n";
+           pr "  if (size == 1 && r == %s)\n" error_code;
+           pr "    /* do_%s has already called reply_with_error */\n" name;
+           pr "    goto done;\n";
+           pr "\n"
       );
 
       (* If there are any FileOut parameters, then the impl must
@@ -6684,8 +6684,8 @@ and generate_fish_cmds () =
       pr "    pod2text (\"%s\", _(\"%s\"), %S);\n"
         name2 shortdesc
         ("=head1 SYNOPSIS\n\n " ^ synopsis ^ "\n\n" ^
-        "=head1 DESCRIPTION\n\n" ^
-        longdesc ^ warnings ^ describe_alias);
+         "=head1 DESCRIPTION\n\n" ^
+         longdesc ^ warnings ^ describe_alias);
       pr "  else\n"
   ) all_functions;
   pr "    display_builtin_command (cmd);\n";
@@ -10176,18 +10176,39 @@ let output_to filename =
   in
   close
 
+let perror msg = function
+  | Unix.Unix_error (err, _, _) ->
+      eprintf "%s: %s\n" msg (Unix.error_message err)
+  | exn ->
+      eprintf "%s: %s\n" msg (Printexc.to_string exn)
+
 (* Main program. *)
 let () =
-  check_functions ();
-
-  if not (Sys.file_exists "HACKING") then (
-    eprintf "\
+  let lock_fd =
+    try Unix.openfile "HACKING" [Unix.O_RDWR] 0
+    with
+    | Unix.Unix_error (Unix.ENOENT, _, _) ->
+       eprintf "\
 You are probably running this from the wrong directory.
 Run it from the top source directory using the command
   src/generator.ml
 ";
-    exit 1
-  );
+       exit 1
+    | exn ->
+       perror "open: HACKING" exn;
+       exit 1 in
+
+  (* Acquire a lock so parallel builds won't try to run the generator
+   * twice at the same time.  Subsequent builds will wait for the first
+   * one to finish.  Note the lock is released implicitly when the
+   * program exits.
+   *)
+  (try Unix.lockf lock_fd Unix.F_LOCK 1
+   with exn ->
+     perror "lock: HACKING" exn;
+     exit 1);
+
+  check_functions ();
 
   let close = output_to "src/guestfs_protocol.x" in
   generate_xdr ();