signal: Move sys_siglist to a compat symbol

The symbol was deprecated by strsignal and its usage imposes issues
such as copy relocations.

Its internal name is changed to __sys_siglist and __sys_sigabbrev to
avoid static linking usage.  The compat code is also refactored, since
both Linux and Hurd usage the same strategy: export the same array with
different object sizes.

The libSegfault change avoids calling strsignal on the SIGFAULT signal
handler (the current usage is already sketchy, adding a call that
potentially issue locale internal function is even sketchier).

Checked on x86_64-linux-gnu and i686-linux-gnu. I also run a check-abi
on all affected platforms.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 7 insertions, 11 deletions

diff --git a/debug/segfault.c b/debug/segfault.c
index 14c64cd..8b59783 100644
--- a/debug/segfault.c
+++ b/debug/segfault.c
@@ -49,20 +49,16 @@
 static const char *fname;
 
 
-/* We better should not use `strerror' since it can call far too many
-   other functions which might fail.  Do it here ourselves.  */
+/* Print the signal number SIGNAL.  Either strerror or strsignal might
+   call local internal functions and these in turn call far too many
+   other functions and might even allocate memory which might fail.  */
 static void
 write_strsignal (int fd, int signal)
 {
-  if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL)
-    {
-      char buf[30];
-      char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
-      WRITE_STRING ("signal ");
-      write (fd, buf, &buf[sizeof (buf)] - ptr);
-    }
-  else
-    WRITE_STRING (_sys_siglist[signal]);
+  char buf[30];
+  char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
+  WRITE_STRING ("signal ");
+  write (fd, buf, &buf[sizeof (buf)] - ptr);
 }