Re: [PATCH v3 0/5] fcntl fortification

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 20/06/23 09:53, Sergey Bugaev wrote:
> On Tue, Jun 20, 2023 at 3:38 PM Maxim Kuvyrkov
> <maxim.kuvyrkov@linaro.org> wrote:
>> We don't set _FORTIFY_SOURCE in our CI's glibc build, but, I think, it comes from Ubuntu's GCC, where it may be enabled by default.  Or are you using Ubuntu and not seeing this with default Ubuntu toolchain?
> 
> I'm not using Ubuntu.
> 
> Do they just set _FORTIFY_SOURCE by default -- i.e. not only when
> building OS packages, but for all compilations? That's... unusual :|

It does for any optimized build:

$ gcc -v 2>&1 | grep 'gcc version'
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04.1)
$ gcc -dM -E - < /dev/null | grep -w _FORTIFY_SOURCE
$ gcc -O2 -dM -E - < /dev/null | grep -w _FORTIFY_SOURCE
#define _FORTIFY_SOURCE 2

And I think this is a common configuration for recent distros.

> 
> It's also concerning that check-installed-headers doesn't check this
> configuration (_FORTIFY_SOURCE with non-GNU C standard), and we're
> only finding out about this by accident. There's a comment in
> check-installed-headers.sh that says:
> 
> # An exhaustive test of feature selection macros would take far too long.
> # These are probably the most commonly used three.
> 
> That makes sense when running the testsuite locally since you want it
> to finish in minutes, not days, but wouldn't checking all combinations
> (or at least _a lot_ more of them) make more sense for CI?
> 

I think it is worth to extend check-installed-headers.sh to include 
fortify as well, specially because it is now being enabled as default
on multiple configurations.