[Bug optimization/12324] [3.4 Regression] [unti-at-a-time] not emitting function referenced from a compound statement

["hubicka at ucw dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12324



------- Additional Comments From hubicka at ucw dot cz  2003-09-26 20:13 -------
Subject: Re:  [3.4 Regression] [unti-at-a-time] not emitting function referenced from a compound statement

> PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12324
> 
> 
> 
> ------- Additional Comments From bernie at develer dot com  2003-09-26 16:29 -------
> Subject: Re:  [3.4 Regression] [unti-at-a-time] not
>  emitting function referenced from a compound statement
> 
> hubicka at ucw dot cz wrote:
> 
> >>------- Additional Comments From bernie at develer dot com  2003-09-25 20:48 -------
> >>Not sure if it's the same bug, but 3.4 outputs
> >>nothing for this code with -O2:
> >>
> >>  static int foo __attribute__((unused)) = 42;
> >>
> >>This breaks the Linux kernel (the __setup() macro).
> >>GCC 3.3.1 did the right thing:
> >>
> >>        .data
> >>        .align 4
> >>        .type   foo, @object
> >>        .size   foo, 4
> >>foo:
> >>        .long   42
> > 
> > You shall use attribute used here.  Attribute unused merely supress the
> > warning, while attribute used makes it to be output.
> 
> Yes, I tried and it works. The documentation does not mention attribute
> used for variables. I think it should be fixed.
> 
> > I will look into the other problem.
> 
> Thanks. That one also breaks the Linux kernel (drivers/net/fec.c uses
> an idiom similar to the test case).
> 
> > Note that attribute used did not work for variables for older GCC, so
> > you need ifdef machinery.
> 
> Do you know the exact GCC version that introduced it? I'd like to provide
> a patch for the kernel. I can only confirm that 'used' works in 3.3.1 for
> variables.

I believe it actually is 3.3.1.  It is safe to test for that version as
no earlier version elliminated unused variables.

Honza
> 
> 
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