Fix a malloc race condition involving strsignal.

A signal can arrive in the middle of a malloc, and Emacs's signal
handler can invoke strsignal, which can invoke malloc, which is
not portable.  This race condition bug makes Emacs hang on GNU/Linux.
Fix it by altering the signal handler so that it does not invoke
strsignal.
* emacs.c (shut_down_emacs): Use safe_strsignal, not strsignal.
* process.c (status_message): Use const pointer, in case strsignal
is #defined to safe_strsignal.
* sysdep.c (sys_siglist, init_signals): Always define and
initialize a substitute sys_siglist if the system does not define
one, even if HAVE_STRSIGNAL.
(safe_strsignal): Rename from strsignal.  Always define,
using sys_siglist.  Return a const pointer.
* syssignal.h (safe_strsignal): New decl.
(strsignal) [!HAVE_STRSIGNAL]: Define in terms of safe_strsignal.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/process.c b/src/process.c
index dfc89809fa5..92bea0d3a27 100644
--- a/src/process.c
+++ b/src/process.c
@@ -570,7 +570,7 @@ status_message (struct Lisp_Process *p)
 
   if (EQ (symbol, Qsignal) || EQ (symbol, Qstop))
     {
-      char *signame;
+      char const *signame;
       synchronize_system_messages_locale ();
       signame = strsignal (code);
       if (signame == 0)