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From f97e07ea807cc6d38774a3888a15091b20645ac6 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 9 Mar 2021 11:22:59 -0800
Subject: [PATCH] Port alternate signal stack to upcoming glibc 2.34
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* src/sysdep.c (sigsegv_stack): Increase size to 64 KiB and align
it to max_align_t. This copies from Gnulib’s c-stack.c, and works
around a portability bug in draft glibc 2.34, which no longer
defines SIGSTKSZ when _GNU_SOURCE is defined.
---
src/sysdep.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/src/sysdep.c b/src/sysdep.c
index 941b4e2fa2..24d8832b2f 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1785,7 +1785,15 @@ handle_arith_signal (int sig)
/* Alternate stack used by SIGSEGV handler below. */
-static unsigned char sigsegv_stack[SIGSTKSZ];
+/* Storage for the alternate signal stack.
+ 64 KiB is not too large for Emacs, and is large enough
+ for all known platforms. Smaller sizes may run into trouble.
+ For example, libsigsegv 2.6 through 2.8 have a bug where some
+ architectures use more than the Linux default of an 8 KiB alternate
+ stack when deciding if a fault was caused by stack overflow. */
+static max_align_t sigsegv_stack[(64 * 1024
+ + sizeof (max_align_t) - 1)
+ / sizeof (max_align_t)];
/* Return true if SIGINFO indicates a stack overflow. */
--
2.29.2
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