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

From: Dirk Gouders
Date: Thu May 23 2013 - 16:33:28 EST

Hi Borislav,

Borislav Petkov <bp@xxxxxxx> 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@xxxxxxxxx>
> 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.

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