On Mon, Aug 23 2021, George Koehler <[email protected]> wrote:
> Hi,
>
> When emacs-27.2p1-gtk3 catches a SIGSEGV and is in the foreground of
> its terminal, then I get a printf %n in /var/log/messages:
>
> Aug 23 17:52:26 wisconsin emacs: *printf used %n: Fatal error %d: %n%s
>
> I first found this by accident, on OpenBSD/powerpc64, after I made a
> wrong diff in my X server. I caused a SIGSEGV in libX11; emacs caught
> it and reached the %n in WRKSRC/src/emacs.c:shut_down_emacs()
>
> To reproduce the %n, it is enough to run "emacs" in one terminal and
> "pkill -SEGV emacs" in another terminal.
Indeed. Months ago I misread the #ifndef as #ifdef DOS_NT, as pointed
out earlier by tb@.
The diff below avoids %n and simplifies the code, I'll suggest something
similar upstream. Tests/input/ok welcome.
Index: Makefile
===================================================================
RCS file: /cvs/ports/editors/emacs/Makefile,v
retrieving revision 1.101
diff -u -p -r1.101 Makefile
--- Makefile 15 Jul 2021 19:26:25 -0000 1.101
+++ Makefile 23 Aug 2021 23:08:30 -0000
@@ -4,7 +4,7 @@ COMMENT= GNU editor: extensible, custom
VERSION= 27.2
DISTNAME= emacs-${VERSION}
-REVISION= 1
+REVISION= 2
CATEGORIES= editors
Index: patches/patch-src_emacs_c
===================================================================
RCS file: patches/patch-src_emacs_c
diff -N patches/patch-src_emacs_c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-src_emacs_c 23 Aug 2021 23:08:30 -0000
@@ -0,0 +1,35 @@
+$OpenBSD$
+
+Don't use printf %n.
+
+Index: src/emacs.c
+--- src/emacs.c.orig
++++ src/emacs.c
+@@ -2445,21 +2445,13 @@ shut_down_emacs (int sig, Lisp_Object stuff)
+ reset_all_sys_modes ();
+ if (sig && sig != SIGTERM)
+ {
+- static char const fmt[] = "Fatal error %d: %n%s\n";
+- char buf[max ((sizeof fmt - sizeof "%d%n%s\n"
+- + INT_STRLEN_BOUND (int) + 1),
+- min (PIPE_BUF, MAX_ALLOCA))];
++ static char const fmt[] = "Fatal error %d: ";
++ char buf[sizeof fmt - strlen ("%d") + INT_STRLEN_BOUND (int) + 1];
+ char const *sig_desc = safe_strsignal (sig);
+- int nlen;
+- int buflen = snprintf (buf, sizeof buf, fmt, sig, &nlen, sig_desc);
+- if (0 <= buflen && buflen < sizeof buf)
+- emacs_write (STDERR_FILENO, buf, buflen);
+- else
+- {
+- emacs_write (STDERR_FILENO, buf, nlen);
+- emacs_write (STDERR_FILENO, sig_desc, strlen (sig_desc));
+- emacs_write (STDERR_FILENO, fmt + sizeof fmt - 2, 1);
+- }
++ snprintf (buf, sizeof buf, fmt, sig);
++ emacs_write (STDERR_FILENO, buf, strlen (buf));
++ emacs_write (STDERR_FILENO, sig_desc, strlen (sig_desc));
++ emacs_write (STDERR_FILENO, "\n", 1);
+ }
+ }
+ #else
--
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