tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Dirk Gouders]

Hello Borislav,

I am having problems with building liblk, but opposed to the recent
problem that Jiri noticed (commit b28b130719af6 Fix _FORTIFY_SOURCE
builds) I am getting errors because _FORTIFY_SOURCE is redefined:

<command-line>:0:0: error: "_FORTIFY_SOURCE" redefined [-Werror]
debugfs.c:1:0: note: this is the location of the previous definition
cc1: all warnings being treated as errors

I guess this is because of different gcc versions being in use.
With gcc-4.7.2 _FORTIFY_SOURCE is defined as

$ gcc -E -dM - < /dev/null | grep -i fortify
#define _FORTIFY_SOURCE ((defined __OPTIMIZE__ && __OPTIMIZE__ > 0) ? 2 : 0)

gcc-4.6.4 uses

#define _FORTIFY_SOURCE 2

and would complain if we set _FORTIFY_SOURCE to something other than 2.

gcc-4.2.2 seems to use no definition of _FORTIFY_SOURCE, by default.

What probably might help in any case is undefining _FORTIFY_SOURCE before
defining it, because as far as I know, there is no problem with
undefining something that is not yet defined, but I could imagine,
others might have more elegant suggestions:

CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -fPIC

Dirk

Re: tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Borislav Petkov]

Hi,

On Wed, May 22, 2013 at 12:00:21PM +0200, Dirk Gouders wrote:
> CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -fPIC

it seems someone else hit this already and fixed it too:

commit d2f32479e5526a1ab3b4e43910fcb279871524ce
Author: Marcin Slusarz <marcin.slusarz@gmail.com>
Date:   Sun Feb 17 16:03:36 2013 +0100

    perf tools: check if -DFORTIFY_SOURCE=2 is allowed

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--

Re: tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Dirk Gouders]

Borislav Petkov <bp@suse.de> writes:

> Hi,
>
> On Wed, May 22, 2013 at 12:00:21PM +0200, Dirk Gouders wrote:
>> CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6
>> -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS)
>> $(EXTRA_CFLAGS) -fPIC
>
> it seems someone else hit this already and fixed it too:
>
> commit d2f32479e5526a1ab3b4e43910fcb279871524ce
> Author: Marcin Slusarz <marcin.slusarz@gmail.com>
> Date:   Sun Feb 17 16:03:36 2013 +0100
>
>     perf tools: check if -DFORTIFY_SOURCE=2 is allowed

Yes, I should have checked the whole log and not just for one file. 
And please ignore my other mail which I sent just when yours arrived ;-)

Dirk

Re: tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Borislav Petkov]

On Wed, May 22, 2013 at 01:27:29PM +0200, Dirk Gouders wrote:
> Yes, I should have checked the whole log and not just for one file.
> And please ignore my other mail which I sent just when yours arrived
> ;-)

No problem at all - I didn't see the fix either until I started looking
at the Makefile so it was a good exersise for both of us.

:-)

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--

Re: tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Dirk Gouders]

Hi Borislav,

Borislav Petkov <bp@suse.de> writes:

> Hi,
>
> On Wed, May 22, 2013 at 12:00:21PM +0200, Dirk Gouders wrote:
>> CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -fPIC
>
> it seems someone else hit this already and fixed it too:
>
> commit d2f32479e5526a1ab3b4e43910fcb279871524ce
> Author: Marcin Slusarz <marcin.slusarz@gmail.com>
> Date:   Sun Feb 17 16:03:36 2013 +0100
>
>     perf tools: check if -DFORTIFY_SOURCE=2 is allowed

I thought about this _FORTIFY_SOURCE test and how the above commit
could/should be adopted to lib/lk/Makefile, and I thought that if it
were true that recent versions of gcc define _FORTIFY_SOURCE by default,
that test could probably be modified and just check gcc's builtin macros to
find out if _FORTIFY_SOURCE has to be defined explicitely and I tried to
find out when gcc started to use _FORTIFY_SOURCE builtin definitions...

In short: all what I said in my initial post was tested with gcc
versions on gentoo machines and it is gentoo that patches gcc so that
_FORTIFY_SOURCE becomes a builtin definition.  Unfortunately I don't
have access to machines running other distributions and can only report
about gcc on gentoo, but even with this limited information I would say
it depends on the distribution in use if -D_FORTIFY_SOURCE=2 is needed
and not on the gcc version.

Sorry for the noise if you already noticed my fault, I felt I should
correct my initial misleading information.

Dirk

Re: tools/lib/lk: redefinition of _FORTIFY_SOURCE (gcc-4.7.2)

[Dirk Gouders]

Dirk Gouders <dirk@gouders.net> writes:

> What probably might help in any case is undefining _FORTIFY_SOURCE before
> defining it, because as far as I know, there is no problem with
> undefining something that is not yet defined, but I could imagine,
> others might have more elegant suggestions:
>
> CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE
> -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -fPIC

More elegant would probably be to look at tools/perf/Makefile and handle
the problem as is done there:

CFLAGS = -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -fPIC

ifeq ($(call try-cc,$(SOURCE_HELLO),$(CFLAGS) -D_FORTIFY_SOURCE=2,-D_FORTIFY_SOURCE=2),y)
               CFLAGS := $(CFLAGS) -D_FORTIFY_SOURCE=2
endif

I tested it here and it works well.

Dirk