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From d98de0bb0b627772625c1acf050ba0dd4b5ac9df Mon Sep 17 00:00:00 2001
From: David Seifert <soap@gentoo.org>
Date: Tue, 5 Jul 2022 11:35:28 +0200
Subject: [PATCH] Perform type punning via union without undefined behavior
* The previous code from c3d7f491e2daebda2413fb3d2935c51df1c50ac7
still contains undefined behavior, since it just creates
temporary pointer variables.
---
src/cmsplugin.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
This patch slightly differs from the upstream commit, because
the lcms2 version used in mupdf is slightly behind the upstream
version.
See: https://github.com/mm2/Little-CMS/commit/d98de0bb0b627772625c1acf050ba0dd4b5ac9df.patch
diff --git a/src/cmsplugin.c b/src/cmsplugin.c
index 556fbc28..b34e3aab 100644
--- a/thirdparty/lcms2/src/cmsplugin.c
+++ b/thirdparty/lcms2/src/cmsplugin.c
@@ -167,17 +167,20 @@ cmsBool CMSEXPORT _cmsReadUInt32Number(cmsContext ContextID, cmsIOHANDLER* io,
cmsBool CMSEXPORT _cmsReadFloat32Number(cmsContext ContextID, cmsIOHANDLER* io, cmsFloat32Number* n)
{
- cmsUInt32Number tmp;
+ union typeConverter {
+ cmsUInt32Number integer;
+ cmsFloat32Number floating_point;
+ } tmp;
_cmsAssert(io != NULL);
- if (io->Read(ContextID, io, &tmp, sizeof(cmsUInt32Number), 1) != 1)
+ if (io->Read(ContextID, io, &tmp.integer, sizeof(cmsUInt32Number), 1) != 1)
return FALSE;
if (n != NULL) {
- tmp = _cmsAdjustEndianess32(tmp);
- *n = *(cmsFloat32Number*)(void*)&tmp;
+ tmp.integer = _cmsAdjustEndianess32(tmp.integer);
+ *n = tmp.floating_point;
// Safeguard which covers against absurd values
if (*n > 1E+20 || *n < -1E+20) return FALSE;
@@ -304,13 +307,14 @@ cmsBool CMSEXPORT _cmsWriteUInt32Number(cmsContext ContextID, cmsIOHANDLER* io,
cmsBool CMSEXPORT _cmsWriteFloat32Number(cmsContext ContextID, cmsIOHANDLER* io, cmsFloat32Number n)
{
- cmsUInt32Number tmp;
-
- _cmsAssert(io != NULL);
-
- tmp = *(cmsUInt32Number*) (void*) &n;
- tmp = _cmsAdjustEndianess32(tmp);
- if (io -> Write(ContextID, io, sizeof(cmsUInt32Number), &tmp) != 1)
+ union typeConverter {
+ cmsUInt32Number integer;
+ cmsFloat32Number floating_point;
+ } tmp;
+
+ tmp.floating_point = n;
+ tmp.integer = _cmsAdjustEndianess32(tmp.integer);
+ if (io -> Write(ContextID, io, sizeof(cmsUInt32Number), &tmp.integer) != 1)
return FALSE;
return TRUE;
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