$ gcc-4.3 --version
| gcc (GCC) 4.3.0 20061215 (experimental)
$ gnulib-tool --with-tests --test
[ interrupt at a convenient location ]
$ .../configure CC=gcc-test
[...]
| checking for working mktime...
This test hangs, because the newer GCC exploits at -O2 the fact that
integer overflow produces undefined behavior: the loop stopping
criterion is never fulfilled:
| for (j = 1; 0 < j; j *= 2)
The patch below fixes that. OK to apply to gnulib/Autoconf?
FYI, here's a short program to expose the issue: it never prints
"isnull" with 'gcc-4.3 -O2'. This isn't the case with 4.1.2, I
haven't tested any other intermediate versions.
Cheers,
Ralf
#include <stdio.h>
int main()
{
int i = 1, j;
for (j=1; j<128; j++) {
i = i + i;
printf("%d %s\n", j, i == 0 ? "isnull" : "nonnull");
}
return 0;
}
2006-12-19 Ralf Wildenhues <[EMAIL PROTECTED]>
Sync from Autoconf:
* m4/mktime.m4 (AC_FUNC_MKTIME): Avoid undefined behavior due to
integer overflow in runtime test, exposed with unreleased GCC
4.3.0.
Index: m4/mktime.m4
===================================================================
RCS file: /cvsroot/gnulib/gnulib/m4/mktime.m4,v
retrieving revision 1.25
diff -u -r1.25 mktime.m4
--- m4/mktime.m4 8 Sep 2006 22:48:25 -0000 1.25
+++ m4/mktime.m4 18 Dec 2006 23:08:35 -0000
@@ -171,7 +171,8 @@
main ()
{
time_t t, delta;
- int i, j;
+ int i;
+ unsigned int j;
/* This test makes some buggy mktime implementations loop.
Give up after 60 seconds; a mktime slower than that
2006-12-19 Ralf Wildenhues <[EMAIL PROTECTED]>
* lib/autoconf/functions.m4 (AC_FUNC_MKTIME): Avoid undefined
behavior due to integer overflow in runtime test, exposed with
unreleased GCC 4.3.0.
Index: lib/autoconf/functions.m4
===================================================================
RCS file: /cvsroot/autoconf/autoconf/lib/autoconf/functions.m4,v
retrieving revision 1.118
diff -u -r1.118 functions.m4
--- lib/autoconf/functions.m4 16 Dec 2006 05:38:41 -0000 1.118
+++ lib/autoconf/functions.m4 18 Dec 2006 23:08:08 -0000
@@ -1125,7 +1125,8 @@
main ()
{
time_t t, delta;
- int i, j;
+ int i;
+ unsigned int j;
/* This test makes some buggy mktime implementations loop.
Give up after 60 seconds; a mktime slower than that
