[glib: 2/3] genviron: Message if g_setenv()/g_unsetenv() are used after threads spawned

[Philip Withnall <pwithnall src gnome org>]

commit 120e6435c7b6a9f8d411b0edc219fbc0895ea1dd
Author: Philip Withnall <withnall endlessm com>
Date:   Thu Jul 25 15:13:17 2019 +0100

    genviron: Message if g_setenv()/g_unsetenv() are used after threads spawned
    
    g_setenv() and g_unsetenv() can never be thread-safe, so emit a message if
    they are used after any threads have been spawned.
    
    This can’t catch interactions between setenv() and g_thread_new(), or
    between g_setenv() and pthread_create(), but it’ll catch most
    misbehaviour in GLib-centric code.
    
    Currently, the message is a `g_debug()` call. Eventually, I’d like to
    upgrade it to a `g_warning()`, but there are a number of GLib tests
    which call g_setenv() after threads have been created, and they need to
    be fixed first. Emitting a `g_debug()` message gives people an
    opportunity to start fixing their code.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    
    Helps: #715

 glib/genviron.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
---
diff --git a/glib/genviron.c b/glib/genviron.c
index c6edb8354..55e1e750e 100644
--- a/glib/genviron.c
+++ b/glib/genviron.c
@@ -42,6 +42,7 @@
 #include "gunicode.h"
 #include "gconvert.h"
 #include "gquark.h"
+#include "gthreadprivate.h"
 
 /* Environ array functions {{{1 */
 static gboolean
@@ -299,6 +300,13 @@ g_setenv (const gchar *variable,
   g_return_val_if_fail (strchr (variable, '=') == NULL, FALSE);
   g_return_val_if_fail (value != NULL, FALSE);
 
+#ifndef G_DISABLE_CHECKS
+  /* FIXME: This will be upgraded to a g_warning() in a future release of GLib.
+   * See https://gitlab.gnome.org/GNOME/glib/issues/715 */
+  if (g_thread_n_created () > 0)
+    g_debug ("setenv()/putenv() are not thread-safe and should not be used after threads are created");
+#endif
+
 #ifdef HAVE_SETENV
   result = setenv (variable, value, overwrite);
 #else
@@ -355,6 +363,13 @@ g_unsetenv (const gchar *variable)
   g_return_if_fail (variable != NULL);
   g_return_if_fail (strchr (variable, '=') == NULL);
 
+#ifndef G_DISABLE_CHECKS
+  /* FIXME: This will be upgraded to a g_warning() in a future release of GLib.
+   * See https://gitlab.gnome.org/GNOME/glib/issues/715 */
+  if (g_thread_n_created () > 0)
+    g_debug ("unsetenv() is not thread-safe and should not be used after threads are created");
+#endif
+
 #ifdef HAVE_UNSETENV
   unsetenv (variable);
 #else /* !HAVE_UNSETENV */