[glib: 2/4] gsubprocess: Clear std buf outputs to NULL on failure

[Philip Withnall <pwithnall src gnome org>]

commit 4795dadde49dac18a7260044a74bf2236c188595
Author: Philip Withnall <withnall endlessm com>
Date:   Thu Oct 11 11:29:48 2018 +1300

    gsubprocess: Clear std buf outputs to NULL on failure
    
    Instead of sometimes returning a non-NULL buffer, always return NULL.
    However, keep the documentation as explicitly returning undefined values
    on failure, so that we can change the behaviour in future if needed.
    
    The return values weren’t defined for failure before, so were
    implicitly returning undefined values.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 gio/gsubprocess.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)
---
diff --git a/gio/gsubprocess.c b/gio/gsubprocess.c
index 23bfbddf2..dcdb84d58 100644
--- a/gio/gsubprocess.c
+++ b/gio/gsubprocess.c
@@ -1784,6 +1784,9 @@ g_subprocess_communicate_finish (GSubprocess   *subprocess,
  *
  * Like g_subprocess_communicate(), but validates the output of the
  * process as UTF-8, and returns it as a regular NUL terminated string.
+ *
+ * On error, @stdout_buf and @stderr_buf will be set to undefined values and
+ * should not be used.
  */
 gboolean
 g_subprocess_communicate_utf8 (GSubprocess   *subprocess,
@@ -1868,6 +1871,7 @@ communicate_result_validate_utf8 (const char            *stream_name,
       if (!g_utf8_validate (*return_location, -1, &end))
         {
           g_free (*return_location);
+          *return_location = NULL;
           g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
                        "Invalid UTF-8 in child %s at offset %lu",
                        stream_name,
@@ -1900,6 +1904,7 @@ g_subprocess_communicate_utf8_finish (GSubprocess   *subprocess,
 {
   gboolean ret = FALSE;
   CommunicateState *state;
+  gchar *local_stdout_buf = NULL, *local_stderr_buf = NULL;
 
   g_return_val_if_fail (G_IS_SUBPROCESS (subprocess), FALSE);
   g_return_val_if_fail (g_task_is_valid (result, subprocess), FALSE);
@@ -1913,11 +1918,11 @@ g_subprocess_communicate_utf8_finish (GSubprocess   *subprocess,
 
   /* TODO - validate UTF-8 while streaming, rather than all at once.
    */
-  if (!communicate_result_validate_utf8 ("stdout", stdout_buf,
+  if (!communicate_result_validate_utf8 ("stdout", &local_stdout_buf,
                                          state->stdout_buf,
                                          error))
     goto out;
-  if (!communicate_result_validate_utf8 ("stderr", stderr_buf,
+  if (!communicate_result_validate_utf8 ("stderr", &local_stderr_buf,
                                          state->stderr_buf,
                                          error))
     goto out;
@@ -1925,5 +1930,14 @@ g_subprocess_communicate_utf8_finish (GSubprocess   *subprocess,
   ret = TRUE;
  out:
   g_object_unref (result);
+
+  if (ret && stdout_buf != NULL)
+    *stdout_buf = g_steal_pointer (&local_stdout_buf);
+  if (ret && stderr_buf != NULL)
+    *stderr_buf = g_steal_pointer (&local_stderr_buf);
+
+  g_free (local_stderr_buf);
+  g_free (local_stdout_buf);
+
   return ret;
 }