https://bugs.gentoo.org/916814
https://salsa.debian.org/georgesk/perl-tk/-/blob/master/debian/patches/80-Fix-STRLEN-vs-int-pointer-confusion-in-Tcl_GetByteAr.patch?ref_type=heads

From a26233c844c52f49ef9cca5f88dd9063aac60d0f Mon Sep 17 00:00:00 2001
From: Niko Tyni <ntyni@debian.org>
Date: Thu, 11 Jan 2024 18:28:58 +0000
Subject: [PATCH] Fix STRLEN vs int pointer confusion in
 Tcl_GetByteArrayFromObj()

Perl 5.37.2, more precisely commit

 https://github.com/Perl/perl5/commit/1ef9039bccbfe64f47f201b6cfb7d6d23e0b08a7

changed the implementation of SvPV() et al., breaking t/balloon.t,
t/canvas2.t and t/photo.t on big-endian 64-bit architectures such as
ppc64 and s390x because StringMatchGIF() no longer recognized GIF files.

This is because Tcl_GetByteArrayFromObj() was calling SvPV() with an int
pointer instead of a correct STRLEN pointer, and the new implementation
is more sensitive to this: it assigns the pointers as-is, resulting in
the int pointer pointing at the wrong end of the 64-bit length.

Other functions taking a length pointer, at least Tcl_GetStringFromObj()
already seem to do things correctly, so presumably this is not a
systematic issue.
---
 objGlue.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/objGlue.c b/objGlue.c
index d4927ea..dbd6a50 100644
--- a/objGlue.c
+++ b/objGlue.c
@@ -627,7 +627,10 @@ Tcl_GetByteArrayFromObj(Tcl_Obj * objPtr, int * lengthPtr)
  sv_utf8_downgrade(objPtr, 0);
  if (lengthPtr)
   {
-   return (unsigned char *) SvPV(objPtr, *lengthPtr);
+   STRLEN len;
+   unsigned char *s = SvPV(objPtr, len);
+   *lengthPtr = len;
+   return s;
   }
  else
   {
-- 
2.30.2