[glib: 4/6] gspawn, win32: fix child stderr when coverage enabled

[Philip Withnall <pwithnall src gnome org>]

commit f7f597c8414f1da9bd5842a8fb26ee6631c18f45
Author: Vasily Galkin <galkin-vv yandex ru>
Date:   Thu Dec 27 00:00:50 2018 +0300

    gspawn, win32: fix child stderr when coverage enabled
    
    This fixes test that were added in previous commit:
    checking for empty stderr failed with coverage enabled, since
    coverage warnings printed from gspawn-win32-helper process were treated
    as child output. This is fixed by removing redirection after child
    finishes execution.
    
    The dup_noninherited renamed to reopen_noninherited,
    since it actually always closes passed file descriptor.

 glib/gspawn-win32-helper.c | 13 ++++++++++---
 glib/gspawn-win32.c        |  8 ++++----
 2 files changed, 14 insertions(+), 7 deletions(-)
---
diff --git a/glib/gspawn-win32-helper.c b/glib/gspawn-win32-helper.c
index 045d90f71..bbb6161ef 100644
--- a/glib/gspawn-win32-helper.c
+++ b/glib/gspawn-win32-helper.c
@@ -179,6 +179,7 @@ main (int ignored_argc, char **ignored_argv)
 {
   int child_err_report_fd = -1;
   int helper_sync_fd = -1;
+  int saved_stderr_fd = -1;
   int i;
   int fd;
   int mode;
@@ -280,6 +281,7 @@ main (int ignored_argc, char **ignored_argv)
        }
     }
 
+  saved_stderr_fd = reopen_noninherited (dup (2), _O_WRONLY);
   if (argv[ARG_STDERR][0] == '-')
     ; /* Nothing */
   else if (argv[ARG_STDERR][0] == 'z')
@@ -315,15 +317,15 @@ main (int ignored_argc, char **ignored_argv)
    */
   if (argv[ARG_CLOSE_DESCRIPTORS][0] == 'y')
     for (i = 3; i < 1000; i++) /* FIXME real limit? */
-      if (i != child_err_report_fd && i != helper_sync_fd)
+      if (i != child_err_report_fd && i != helper_sync_fd && i != saved_stderr_fd)
         if (_get_osfhandle (i) != -1)
           close (i);
 
   /* We don't want our child to inherit the error report and
    * helper sync fds.
    */
-  child_err_report_fd = dup_noninherited (child_err_report_fd, _O_WRONLY);
-  helper_sync_fd = dup_noninherited (helper_sync_fd, _O_RDONLY);
+  child_err_report_fd = reopen_noninherited (child_err_report_fd, _O_WRONLY);
+  helper_sync_fd = reopen_noninherited (helper_sync_fd, _O_RDONLY);
 
   /* argv[ARG_WAIT] is "w" to wait for the program to exit */
   if (argv[ARG_WAIT][0] == 'w')
@@ -351,6 +353,11 @@ main (int ignored_argc, char **ignored_argv)
 
   saved_errno = errno;
 
+  /* Some coverage warnings may be printed on stderr during this process exit.
+   * Remove redirection so that they would go to original stderr
+   * instead of being treated as part of stderr of child process.
+   */
+  dup2 (saved_stderr_fd, 2);
   if (handle == -1 && saved_errno != 0)
     {
       int ec = (saved_errno == ENOENT)
diff --git a/glib/gspawn-win32.c b/glib/gspawn-win32.c
index 3a746914b..c4cc8593b 100644
--- a/glib/gspawn-win32.c
+++ b/glib/gspawn-win32.c
@@ -105,8 +105,8 @@ enum {
 };
 
 static int
-dup_noninherited (int fd,
-                 int mode)
+reopen_noninherited (int fd,
+                    int mode)
 {
   HANDLE filehandle;
 
@@ -606,7 +606,7 @@ do_spawn_with_fds (gint                 *exit_status,
    * helper process, and the started actual user process. As such that
    * shouldn't harm, but it is unnecessary.
    */
-  child_err_report_pipe[0] = dup_noninherited (child_err_report_pipe[0], _O_RDONLY);
+  child_err_report_pipe[0] = reopen_noninherited (child_err_report_pipe[0], _O_RDONLY);
 
   if (flags & G_SPAWN_FILE_AND_ARGV_ZERO)
     {
@@ -625,7 +625,7 @@ do_spawn_with_fds (gint                 *exit_status,
    * process won't read but won't get any EOF either, as it has the
    * write end open itself.
    */
-  helper_sync_pipe[1] = dup_noninherited (helper_sync_pipe[1], _O_WRONLY);
+  helper_sync_pipe[1] = reopen_noninherited (helper_sync_pipe[1], _O_WRONLY);
 
   if (stdin_fd != -1)
     {