Try to avoid malloc SEGVs on Cygwin.

* callproc.c, process.h (block_child_signal, unblock_child_signal):
Now extern.
* emacs.c (main): Catch SIGCHLD just before initializing gfilenotify.
* process.c (catch_child_signal): Block SIGCHLD while futzing with
the SIGCHLD handler, since the code is not atomic and (due to glib)
signals may be arriving now.
* sysdep.c (init_signals): Do not catch child signals here;
'main' now does that later, at a safer time.

Fixes: debbugs:14569

1 files changed, 7 insertions, 0 deletions

diff --git a/src/emacs.c b/src/emacs.c
index 13f6d117ebc..c5b32c7c0e7 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1257,6 +1257,13 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
     tzset ();
 #endif /* MSDOS */
 
+  /* Do this after initializing the memory allocator, since it uses
+     glib and glib uses malloc.  And do it before anything else that
+     invokes glib, to avoid potential races among glib subthreads in
+     Cygwin glib.  gfilenotify invokes glib, so this can't be delayed
+     further.  */
+  catch_child_signal ();
+
 #ifdef HAVE_GFILENOTIFY
   globals_of_gfilenotify ();
 #endif