disable fork-malloc-exec for non-glibc-systems

Calling malloc() after fork is undefined behaviour if the process is
multi-threaded. locks held by a thread on fork() will never be released.
malloc() is usally protected by a lock and can therefore deadlock. glibc
is known not to deadlock in this case.

This commit does not rule out other problems on glibc-systems, but fixes an
issue on musl-libc-systems. Only restricting to async-signal safe functions
between fork() and exec() prevents undefined behaviour for sure. See
signal-safety(7).

(cherry picked from commit 3fab06d68f5940cde89fb9c7e647bdc48bc7b253)

diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index e511afc..06cea5a 100644 (file)
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -4471,7 +4471,7 @@ _dbus_close_all (void)
 {
   int maxfds, i;
 
-#ifdef __linux__
+#if defined(__linux__) && defined(__GLIBC__)
   DIR *d;
 
   /* On Linux we can optimize this a bit if /proc is available. If it