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