Unfortunately Debian Stable (i.e. Etch), which is relatively popular for server

use, is still using 4.1.1  :-(  (The current gcc package is gcc-4.1.1-21)
   I have not looked to see if Debian Stable's gcc-4.1.1-21 has been patched for

the currently discussed __weak bug.
   -- Chris
Chris Knadle

Chris.Knadle@coredump.us

--

Hi Chris,
(I fixed the corrupted CC and Reply-to: address from your email.)
I checked and it has been patched in 4.1.1-21. This would make checking for

4.1.1 via __GNUC_PATCHLEVEL__ potentially invalid, as patched distro

compilers may (and in this case do) have this fixed.
--

Cheers,

Alistair.
137/1 Warrender Park Road, Edinburgh, UK.

--

Not a problem for the Debian Stable Version, as someone already wrote, it

gcc (GCC) 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

Copyright (C) 2006 Free Software Foundation, Inc.

This is free software; see the source for copying conditions.  There is NO

warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
c'ya

sven
-- 
The Internet treats censorship as a routing problem, and routes around

it. (John Gilmore on http://www.cygnus.com/~gnu/)

--

Is it possible to cook up a small sample file we could build as part

of the kernel build. If it fails => error out.

If someone comes up with the code I shall try to integrate it

in the build system.
	Sam

--

On Friday 02 May 2008 11:43:48 Sam Ravnborg wrote:
The GCC PR has a test case for this regression which might be usable.
http://gcc.gnu.org/viewcvs/branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/...
--

Cheers,

Alistair.
137/1 Warrender Park Road, Edinburgh, UK.

--

OK, can anyone confirm that this fails to build which a

buggy gcc:
void __attribute__((weak)) func(void)

{

    /* no code */

}
int main()

{

    func();

    return 0;

}
	Sam

--

I think the problem is that main() would have no call to func(), not

that it wouldn't build.
Does making func noinline fix it?  I wonder if we should make __weak

implicitly make the function noinline too.
    J

--

Of course it doesn't fail to build.  With buggy gcc it will be optimized

to

void __attribute__((weak)) func (void)

{

}
int main ()

{

  return 0;

}
(similarly how all recent gccs optimize this without the weak attribute)

while non-buggy gcc keeps the func call.

So, you either need to grep the assembly (that's what e.g. the GCC testcase

does), or you can e.g. use a runtime testcase:

extern void abort (void);

void __attribute__((weak)) func (void) { }

int main () { func (); abort (); }

in one compilation unit and

extern void exit (int);

void func (void) { exit (0); }

in another one.  I doubt a runtime testcase is acceptable though for the

kernel, as the cross compiler used to build the kernel might not be able to

create userland executables (missing C library, etc.).
	Jakub

--

I assume the GCC testsuite has the same generic problem, which is probably why

it uses the -fdump-tree-optimized parameter to gcc. For example:
alistair@just:~$ cat test.c

void __attribute__((weak)) func(void)

{

    /* no code */

}
int main()

{

    func();

    return 0;

}
alistair@just:~$ gcc -O2 -fdump-tree-optimized test.c

alistair@just:~$ rm -f a.out

alistair@just:~$ cat test.c*.optimized | egrep "func \\(\\);"

  func ();
Ergo, my compiler isn't buggy. As this doesn't require a runtime test I think

it would be OK for the kernel.
Of course, whether or not it's worth it is now debatable, given the

information Sven-Haegar Koch provided (Debian's GCC version number is

actually 4.1.2).
--

Cheers,

Alistair.
137/1 Warrender Park Road, Edinburgh, UK.

--

Well the package version string is 4.1.1, but the compiler thinks it's

4.1.2, at least on i386, amd64 and ia64:
$ cc -v

gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
A small test program agrees:
        printf("%d\n", __GNUC_PATCHLEVEL__);

$ ./a.out

2
Mike.
--