Re: [RFC] Eliminate NESTED_ATTR_FUNC

Re: [RFC] Eliminate NESTED_ATTR_FUNC

[Vladimir 'phcoder' Serbinenko]

> Hi,
>
> Oh, I was wrong previously, gcc does respect __attribute__
> ((__regparm__ (3))) flag (I forget to add -Os so it still uses stack
> to store value). And the bug is still there ! Try this test program:
I confirm with gcc-4.4
This is a grave problem then. This check was added by Marco Gerards
(maintainer) in 2003. He added a workaround but I don't believe such
behaviour to be correct. We're both GNU projects. IMO the correct
action would have been to report the bug to gcc-devel and refuse to
compile unless bug is fixed. This way users would update to newer gcc
patchlevel (e.g. 4.2.(X+1) instead of 4.2.X) instead of compiling with
buggy compiler. One GNU project shouldn't have expensive workaround
(we had bugs because of NESTED_FUNC_ATTR misuse)
Now we're in feature freeze but I hope in the future we'll be able to
change to correct behaviour when freeze is over.
>
> #include <stdio.h>
>
> void foo (int a, int b, void (*hook) (int aa, int bb, int cc))
> {
>  b += a;
>  hook (a, b, a + b);
> }
>
> void qq (int a)
> {
>  auto void q1 (int aa, int bb, int cc);
>  void q1 (int aa, int bb, int cc)
>    {
>      printf ("%d %d %d\n", a, aa + bb, cc);
>    }
>
>  foo (a, a + 1, q1);
> }
>
> int main()
> {
>  qq (10);
> }
>
> Compile with:
> gcc -m32 -mregparm=3 -Os test.c
>
> ./a.out
> 10 31 -6674368
>
> gcc is 4.3.4 from debian.
> ---
> Bean
>
> gitgrub home: http://github.com/grub/grub/
> my fork page: http://github.com/bean123/grub/
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel
>



-- 
Regards
Vladimir 'phcoder' Serbinenko

Personal git repository: http://repo.or.cz/w/grub2/phcoder.git

Re: [RFC] Eliminate NESTED_ATTR_FUNC

[Paolo Bonzini]

>> #include<stdio.h>
>>
>> void foo (int a, int b, void (*hook) (int aa, int bb, int cc))
>> {
>>   b += a;
>>   hook (a, b, a + b);
>> }
>>
>> void qq (int a)
>> {
>>   auto void q1 (int aa, int bb, int cc);
>>   void q1 (int aa, int bb, int cc)
>>     {
>>       printf ("%d %d %d\n", a, aa + bb, cc);
>>     }
>>
>>   foo (a, a + 1, q1);
>> }
>>
>> int main()
>> {
>>   qq (10);
>> }
>>
>> Compile with:
>> gcc -m32 -mregparm=3 -Os test.c
>>
>> ./a.out
>> 10 31 -6674368

Ok, this was the only important part of the message to us GCC hackers. :-)

Can you please report a bug in bugzilla, saying which versions work and 
which fail?  Also can you write in the report what was your analysis 
with respect to regparm?

Thanks!

Paolo

Re: [RFC] Eliminate NESTED_ATTR_FUNC

[Vladimir 'phcoder' Serbinenko]

On Thu, Sep 3, 2009 at 5:54 PM, Paolo Bonzini<bonzini@gnu.org> wrote:
>
>>> #include<stdio.h>
>>>
>>> void foo (int a, int b, void (*hook) (int aa, int bb, int cc))
>>> {
>>>  b += a;
>>>  hook (a, b, a + b);
>>> }
>>>
>>> void qq (int a)
>>> {
>>>  auto void q1 (int aa, int bb, int cc);
>>>  void q1 (int aa, int bb, int cc)
>>>    {
>>>      printf ("%d %d %d\n", a, aa + bb, cc);
>>>    }
>>>
>>>  foo (a, a + 1, q1);
>>> }
>>>
>>> int main()
>>> {
>>>  qq (10);
>>> }
>>>
>>> Compile with:
>>> gcc -m32 -mregparm=3 -Os test.c
>>>
>>> ./a.out
>>> 10 31 -6674368
>
> Ok, this was the only important part of the message to us GCC hackers. :-)
>
> Can you please report a bug in bugzilla, saying which versions work and
> which fail?  Also can you write in the report what was your analysis with
> respect to regparm?
Done by Robert Millan here: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41246
>
> Thanks!
>
> Paolo
>



-- 
Regards
Vladimir 'phcoder' Serbinenko

Personal git repository: http://repo.or.cz/w/grub2/phcoder.git