From 368ac47cccd4ffca6e83a26289c152a32c2ea385 Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Wed, 17 Apr 2019 15:45:15 +1000
Subject: [PATCH] (perl #134035) ensure sv_gets() handles a signal handler
 modifying sv
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At a very basic level at least.

In the ticket cases, a signal handler is modifying (and reallocating
PVX) the sv, while sv_gets() retained a pointer to the inside of the
SV.

This still has some problems, like if the signal handler ends up
shortening SV, there may be old data left between the old position
and the new position, but I think that's a case of user error.

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 sv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sv.c b/sv.c
index 8bc0af0c16..83de536ad7 100644
--- a/sv.c
+++ b/sv.c
@@ -8755,7 +8755,10 @@ Perl_sv_gets(pTHX_ SV *const sv, PerlIO *const fp, I32 append)
 
             Note we have to deal with the char in 'i' if we are not at EOF
         */
+        bpx = bp - (STDCHAR*)SvPVX_const(sv);
+        /* signals might be called here, possibly modifying sv */
 	i   = PerlIO_getc(fp);		/* get more characters */
+        bp = (STDCHAR*)SvPVX_const(sv) + bpx;
 
 	DEBUG_Pv(PerlIO_printf(Perl_debug_log,
 	   "Screamer: post: FILE * thinks ptr=%" UVuf ", cnt=%" IVdf ", base=%" UVuf "\n",
-- 
2.20.1