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| author | Jakub Jelinek <jakub@redhat.com> | 2024-04-03 10:02:35 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2024-06-11 12:35:34 +0200 |
| commit | 9987fe67cf6211515d8ebf6528cc83c77dfb5bf3 (patch) | |
| tree | a709fe7be0ab101561e9d7b2f9d9876480f089b9 | |
| parent | 81c300bf6836505ef1df1c4430972863c732fc14 (diff) | |
| download | gcc-9987fe67cf6211515d8ebf6528cc83c77dfb5bf3.zip gcc-9987fe67cf6211515d8ebf6528cc83c77dfb5bf3.tar.gz gcc-9987fe67cf6211515d8ebf6528cc83c77dfb5bf3.tar.bz2 | |
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)
| -rw-r--r-- | libquadmath/printf/printf_fp.c | 2 | ||||
| -rw-r--r-- | 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 8effcee..9968aa5 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 a40a6b0..ddb4135 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)) |