On 06/21/11 12:43, Ralf Wildenhues wrote:
> It would be good to make sure GCC 4.6 whole program/link time
> optimization doesn't defeat this
It doesn't, at least, not on my platform (Fedora 14 x86-64 + GCC 4.6.0).
* Paul Eggert wrote on Tue, Jun 21, 2011 at 12:19:25AM CEST:
> Testing this is not something for the fainthearted, as it requires
> access to all sorts of strange hosts. However, it does seem to
> defeat GCC 4.6.0's tail-recursion optimization (-O0 through -O4)
> on my platform, which is what is w
On 06/20/11 10:54, Eric Blake wrote:
> Hmm, we'll need to backport this improved stack-direction testing to
> gnulib and libsigsegv, then,
Makes sense. I just pushed this gnulib patch, to do that part.
Testing this is not something for the fainthearted, as it requires
access to all sorts of str
On 06/17/2011 04:21 AM, Andy Wingo wrote:
> wingo@badger:/tmp$ gcc -O1 -o test foo.c
> wingo@badger:/tmp$ ./test; echo $?
> 1
> wingo@badger:/tmp$ gcc -O3 -o test foo.c
> wingo@badger:/tmp$ ./test; echo $?
> 0
If I understand correctly, 0 is a correct result, just not optimal.
Improve
[adding bug-gnulib]
On 06/19/2011 11:35 PM, Paul Eggert wrote:
> On 06/19/11 12:01, Andy Wingo wrote:
>> No, this program also exhibits the same incorrect behavior, for purposes
>> of stack growth checking.
>
> Thanks, I guess we'll have to turn it up a notch. How about the
> following test prog
On Mon, Jun 20, 2011 at 11:25, Andrew W. Nosenko
wrote:
> On Sun, Jun 19, 2011 at 22:03, Andy Wingo wrote:
>> Hi,
>>
>> On Sat 18 Jun 2011 22:25, "Andrew W. Nosenko"
>> writes:
>>
>>> On Fri, Jun 17, 2011 at 13:21, Andy Wingo wrote:
wingo@badger:/tmp$ cat foo.c
int
find_stack
On Sun, Jun 19, 2011 at 22:03, Andy Wingo wrote:
> Hi,
>
> On Sat 18 Jun 2011 22:25, "Andrew W. Nosenko"
> writes:
>
>> On Fri, Jun 17, 2011 at 13:21, Andy Wingo wrote:
>>> wingo@badger:/tmp$ cat foo.c
>>> int
>>> find_stack_direction ()
>>> {
>>> static char *addr = 0;
>>
>> Try to rewr
On Mon, Jun 20, 2011 at 09:50, Paul Eggert wrote:
> On 06/19/11 23:35, Ralf Wildenhues wrote:
>> If you don't use volatile, the compiler is pretty much free to give you
>> whatever answer it likes today.
>
> It's true that the test relies on undefined behavior, and so the
> compiler is free to do
On Mon 20 Jun 2011 07:35, Paul Eggert writes:
> On 06/19/11 12:01, Andy Wingo wrote:
>> No, this program also exhibits the same incorrect behavior, for purposes
>> of stack growth checking.
>
> Thanks, I guess we'll have to turn it up a notch. How about the
> following test program?
Works for m
On 06/19/11 23:35, Ralf Wildenhues wrote:
> If you don't use volatile, the compiler is pretty much free to give you
> whatever answer it likes today.
It's true that the test relies on undefined behavior, and so the
compiler is free to do whatever it wants, but I don't see how
adding "volatile" hel
Hello Paul,
* Paul Eggert wrote on Mon, Jun 20, 2011 at 07:35:37AM CEST:
> On 06/19/11 12:01, Andy Wingo wrote:
> > No, this program also exhibits the same incorrect behavior, for purposes
> > of stack growth checking.
>
> Thanks, I guess we'll have to turn it up a notch. How about the
> followi
On 06/19/11 12:01, Andy Wingo wrote:
> No, this program also exhibits the same incorrect behavior, for purposes
> of stack growth checking.
Thanks, I guess we'll have to turn it up a notch. How about the
following test program?
int
find_stack_direction (int *addr, int depth)
{
int dir, dummy =
Does it work to use the following test program instead?
int
find_stack_direction (char *addr)
{
char dummy;
return (! addr ? find_stack_direction (&dummy)
: addr < &dummy ? 1 : -1);
}
int
main (void)
{
return find_stack_direction (0) < 0;
}
This, essentially, is the fix I just pu
On Fri, Jun 17, 2011 at 13:21, Andy Wingo wrote:
> Hello,
>
> The following transcript indicates a problem with the stack growth
> direction check, present at functions.m4:328 in autoconf 2.68:
>
> wingo@badger:/tmp$ cat foo.c
> int
> find_stack_direction ()
> {
> static char *addr = 0;
Tr
Hi,
On Sat 18 Jun 2011 22:25, "Andrew W. Nosenko"
writes:
> On Fri, Jun 17, 2011 at 13:21, Andy Wingo wrote:
>> wingo@badger:/tmp$ cat foo.c
>> int
>> find_stack_direction ()
>> {
>> static char *addr = 0;
>
> Try to rewrite this line as
> volatile static char *addr = 0;
> It sh
On Sat 18 Jun 2011 23:42, Paul Eggert writes:
> Does it work to use the following test program instead?
>
> int
> find_stack_direction (char *addr)
> {
> char dummy;
> return (! addr ? find_stack_direction (&dummy)
> : addr < &dummy ? 1 : -1);
> }
>
> int
> main (void)
> {
> retur
Hello,
The following transcript indicates a problem with the stack growth
direction check, present at functions.m4:328 in autoconf 2.68:
wingo@badger:/tmp$ cat foo.c
int
find_stack_direction ()
{
static char *addr = 0;
auto char dummy;
if (addr == 0)
{
addr = &d
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