https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114533
Bug ID: 114533
Summary: libquadmath: printf: fix misaligned access on args
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libquadmath
Assignee: unassigned at gcc dot gnu.org
Reporter: doko at gcc dot gnu.org
Target Milestone: ---
reported at
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/647635.html
On x86, this compiles into movdqa which segfaults on unaligned access.
This kind of failure has been seen when running against glibc 2.39,
which incidentally changed the printf implementation to move away from
alloca() for this data to instead append it at the end of an existing
"scratch buffer", with arbitrary alignment, whereas alloca() was
probably more likely to be naturally aligned.
Tested by adding the patch to the Ubuntu gcc-14 package in
https://launchpad.net/~schopin/+archive/ubuntu/libquadmath
Signed-off-by: Simon Chopin <simon.cho...@canonical.com>
---
libquadmath/printf/printf_fp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libquadmath/printf/printf_fp.c b/libquadmath/printf/printf_fp.c
index 8effcee88fa..d86aa650d38 100644
--- a/libquadmath/printf/printf_fp.c
+++ b/libquadmath/printf/printf_fp.c
@@ -363,7 +363,7 @@ __quadmath_printf_fp (struct __quadmath_printf_file *fp,
/* Fetch the argument value. */
{
- fpnum = **(const __float128 **) args[0];
+ memcpy(&fpnum, *(void* const *) args[0], sizeof(fpnum));
/* Check for special values: not a number or infinity. */
if (isnanq (fpnum))
