gdesktopappinfo: Use sh rather than gio-launch-desktop

There were some problems about where to install `gio-launch-desktop` to
support multiarch systems without circular dependencies. Simon McVittie
suggested that, actually, given the current set of platforms supported
by `GDesktopAppInfo` (they’re all POSIX), we could just use `sh`.

That simplifies things nicely. `gio-launch-desktop` can always be
resurrected (and the multiarch debate continued and resolved) if needed
in future.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Fixes: #1633

gio/gdesktopappinfo.c

@@ -160,7 +160,6 @@ static const gchar    *desktop_file_dirs_config_dir = NULL;
 static DesktopFileDir *desktop_file_dir_user_config = NULL;  /* (owned) */
 static DesktopFileDir *desktop_file_dir_user_data = NULL;  /* (owned) */
 static GMutex          desktop_file_dir_lock;
-static const gchar    *gio_launch_desktop_path = NULL;
 
 /* Monitor 'changed' signal handler {{{2 */
 static void desktop_file_dir_reset (DesktopFileDir *dir);
@@ -2737,6 +2736,14 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo            *info,
       char *sn_id = NULL;
       char **wrapped_argv;
       int i;
+      const gchar * const wrapper_argv[] =
+        {
+          "/bin/sh",
+          "-e",
+          "-u",
+          "-c", "export GIO_LAUNCHED_DESKTOP_FILE_PID=$$; exec \"$@\"",
+          "sh",  /* argv[0] for sh */
+        };
 
       old_uris = dup_uris;
       if (!expand_application_parameters (info, exec_line, &dup_uris, &argc, &argv, error))
@@ -2778,26 +2785,26 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo            *info,
           g_list_free_full (launched_files, g_object_unref);
         }
 
-      if (g_once_init_enter (&gio_launch_desktop_path))
+      /* Wrap the @argv in a command which will set the
-        {
+       * `GIO_LAUNCHED_DESKTOP_FILE_PID` environment variable. We can’t set this
-          const gchar *tmp;
+       * in @envp along with `GIO_LAUNCHED_DESKTOP_FILE` because we need to know
-
+       * the PID of the new forked process. We can’t use setenv() between fork()
-          /* Allow test suite to specify path to gio-launch-desktop */
+       * and exec() because we’d rather use posix_spawn() for speed.
-          tmp = g_getenv ("GIO_LAUNCH_DESKTOP");
+       *
-
+       * `sh` should be available on all the platforms that `GDesktopAppInfo`
-          /* Fall back on usual searching in $PATH */
+       * currently supports (since they are all POSIX). If additional platforms
-          if (tmp == NULL)
+       * need to be supported in future, it will probably have to be replaced
-            tmp = "gio-launch-desktop";
+       * with a wrapper program (grep the GLib git history for
-          g_once_init_leave (&gio_launch_desktop_path, tmp);
+       * `gio-launch-desktop` for an example of this which could be
-        }
+       * resurrected). */
-
+      wrapped_argv = g_new (char *, argc + G_N_ELEMENTS (wrapper_argv) + 1);
-      wrapped_argv = g_new (char *, argc + 2);
-      wrapped_argv[0] = g_strdup (gio_launch_desktop_path);
 
+      for (i = 0; i < G_N_ELEMENTS (wrapper_argv); i++)
+        wrapped_argv[i] = g_strdup (wrapper_argv[i]);
       for (i = 0; i < argc; i++)
-        wrapped_argv[i + 1] = g_steal_pointer (&argv[i]);
+        wrapped_argv[i + G_N_ELEMENTS (wrapper_argv)] = g_steal_pointer (&argv[i]);
 
-      wrapped_argv[i + 1] = NULL;
+      wrapped_argv[i + G_N_ELEMENTS (wrapper_argv)] = NULL;
       g_free (argv);
       argv = NULL;
 

gio/gio-launch-desktop.c

@@ -1,52 +0,0 @@
-/* GIO - GLib Input, Output and Streaming Library
- *
- * Copyright (C) 2018 Endless Mobile, Inc.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General
- * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
- *
- * Author: Daniel Drake <drake@endlessm.com>
- */
-
-/*
- * gio-launch-desktop: GDesktopAppInfo helper
- * Executable wrapper to set GIO_LAUNCHED_DESKTOP_FILE_PID
- * There are complications when doing this in a fork()/exec() codepath,
- * and it cannot otherwise be done with posix_spawn().
- * This wrapper is designed to be minimal and lightweight.
- * It does not even link against glib.
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-int
-main (int argc, char *argv[])
-{
-  pid_t pid = getpid ();
-  char buf[50];
-  int r;
-
-  if (argc < 2)
-    return -1;
-
-  r = snprintf (buf, sizeof (buf), "GIO_LAUNCHED_DESKTOP_FILE_PID=%ld", (long) pid);
-  if (r >= sizeof (buf))
-    return -1;
-
-  putenv (buf);
-
-  return execvp (argv[1], argv + 1);
-}

gio/meson.build

@@ -416,12 +416,6 @@ if host_system != 'windows'
     contenttype_sources += files('gcontenttype.c')
     appinfo_sources += files('gdesktopappinfo.c')
     gio_unix_include_headers += files('gdesktopappinfo.h')
-
-    executable('gio-launch-desktop', 'gio-launch-desktop.c',
-      install : true,
-      c_args : gio_c_args,
-      # intl.lib is not compatible with SAFESEH
-      link_args : noseh_link_args)
   endif
 
   subdir('xdgmime')

gio/tests/meson.build

@@ -96,7 +96,6 @@ test_env = environment()
 test_env.set('G_TEST_SRCDIR', meson.current_source_dir())
 test_env.set('G_TEST_BUILDDIR', meson.current_build_dir())
 test_env.set('GIO_MODULE_DIR', '')
-test_env.set('GIO_LAUNCH_DESKTOP', meson.build_root() + '/gio/gio-launch-desktop')
 
 # Check for libdbus1 - Optional - is only used in the GDBus test cases
 # 1.2.14 required for dbus_message_set_serial