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* [gcc r13-8625] libquadmath: Don't assume the storage for __float128 arguments is aligned [PR114533]
@ 2024-04-21 4:08 Jakub Jelinek
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From: Jakub Jelinek @ 2024-04-21 4:08 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:cc39bd532d4de1ba0b2785246fb6fdd63ec2e92c
commit r13-8625-gcc39bd532d4de1ba0b2785246fb6fdd63ec2e92c
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Apr 3 10:02:35 2024 +0200
libquadmath: Don't assume the storage for __float128 arguments is aligned [PR114533]
With the register_printf_type/register_printf_modifier/register_printf_specifier
APIs the C library is just told the size of the argument and is provided with
a callback to fetch the argument from va_list using va_arg into C library provided
memory. The C library isn't told what alignment requirement it has, but we were
using direct load of a __float128 value from that memory which assumes
__alignof (__float128) alignment.
The following patch fixes that by using memcpy instead.
I haven't been able to reproduce an actual crash, tried
#include <quadmath.h>
#include <stdlib.h>
#include <stdio.h>
int main ()
{
__float128 r;
int prec = 20;
int width = 46;
char buf[128];
r = 2.0q;
r = sqrtq (r);
int n = quadmath_snprintf (buf, sizeof buf, "%+-#*.20Qe", width, r);
if ((size_t) n < sizeof buf)
printf ("%s\n", buf);
/* Prints: +1.41421356237309504880e+00 */
quadmath_snprintf (buf, sizeof buf, "%Qa", r);
if ((size_t) n < sizeof buf)
printf ("%s\n", buf);
/* Prints: 0x1.6a09e667f3bcc908b2fb1366ea96p+0 */
n = quadmath_snprintf (NULL, 0, "%+-#46.*Qe", prec, r);
if (n > -1)
{
char *str = malloc (n + 1);
if (str)
{
quadmath_snprintf (str, n + 1, "%+-#46.*Qe", prec, r);
printf ("%s\n", str);
/* Prints: +1.41421356237309504880e+00 */
}
free (str);
}
printf ("%+-#*.20Qe\n", width, r);
printf ("%Qa\n", r);
printf ("%+-#46.*Qe\n", prec, r);
printf ("%d %Qe %d %Qe %d %Qe\n", 1, r, 2, r, 3, r);
return 0;
}
In any case, I think memcpy for loading from it is right.
2024-04-03 Simon Chopin <simon.chopin@canonical.com>
Jakub Jelinek <jakub@redhat.com>
PR libquadmath/114533
* printf/printf_fp.c (__quadmath_printf_fp): Use memcpy to copy
__float128 out of args.
* printf/printf_fphex.c (__quadmath_printf_fphex): Likewise.
Signed-off-by: Simon Chopin <simon.chopin@canonical.com>
(cherry picked from commit 8455d6f6cd43b7b143ab9ee19437452fceba9cc9)
Diff:
---
libquadmath/printf/printf_fp.c | 2 +-
libquadmath/printf/printf_fphex.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/libquadmath/printf/printf_fp.c b/libquadmath/printf/printf_fp.c
index 8effcee88fa..9968aa5307c 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, *(const void *const *) args[0], sizeof (fpnum));
/* Check for special values: not a number or infinity. */
if (isnanq (fpnum))
diff --git a/libquadmath/printf/printf_fphex.c b/libquadmath/printf/printf_fphex.c
index a40a6b00945..ddb413563c6 100644
--- a/libquadmath/printf/printf_fphex.c
+++ b/libquadmath/printf/printf_fphex.c
@@ -163,7 +163,8 @@ __quadmath_printf_fphex (struct __quadmath_printf_file *fp,
/* Fetch the argument value. */
{
- fpnum.value = **(const __float128 **) args[0];
+ memcpy (&fpnum.value, *(const void *const *) args[0],
+ sizeof (fpnum.value));
/* Check for special values: not a number or infinity. */
if (isnanq (fpnum.value))
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