MDEV-31727: pcre stack size not functioning on clang-16

[grooverdan]

Thanks Zhixu Liu for the great bug report.

• The Jira issue number for this PR is: MDEV-31727

Description

noinline attribute was being ignored by clang-16 and reporting 32 stack size on Gentoo, 16 locally on Fedora 38.

Based on https://stackoverflow.com/questions/54481855/clang-ignoring-attribute-noinline changed the noinline to noopt.

After that the -pcre_exec(NULL, NULL, NULL, -999, -999, 0, NULL, 0) returned 1056, simlar to gcc.

From https://bugs.gentoo.org/910188.

How can this PR be tested?

Manual compile against bundled pcre with code per gentoo bug report.

Basing the PR against the correct MariaDB version

• This is a new feature and the PR is based against the latest MariaDB development branch.
• [ X ] This is a bug fix and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• [ X ] I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• [ X ] For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

[clan]

Does gcc support attribute((optnone)) ?
If not, maybe we should add a compiler check?

[grooverdan]

gcc-13.1.1 doesn't support the optnone, and clang didn't support the noclone, but both seem to ignore the ones they don't support.

[vuvova]

ideally, the fix should work with the system pcre too. If we patch the bundled version, MariaDB will not be able to use system pcre anymore

UPD: ok, it's 10.4-only, and we check whether system pcre is usable or not, then I suppose we can fix only bundled. It'll be up to Gentoo/Fedora to patch their distro version of pcre if they want to.

[grooverdan]

And luckily for the most part system builds are still gcc based.

@vuvova still got an account to update https://bugs.exim.org/show_bug.cgi?id=2173, apparently other's had trouble registering.

[thesamesam]

ideally, the fix should work with the system pcre too. If we patch the bundled version, MariaDB will not be able to use system pcre anymore

UPD: ok, it's 10.4-only, and we check whether system pcre is usable or not, then I suppose we can fix only bundled. It'll be up to Gentoo/Fedora to patch their distro version of pcre if they want to.

Done for Gentoo, thanks!

[dr-m]

I wonder if this is in any way related to MDEV-31605, which involves JSON functions.

I was thinking of adding the following to include/my_compiler.h:

#ifdef __clang__
# define ATTRIBUTE_OPTNONE __attribute__((optnone))
#elif defined __GNUC__
# define ATTRIBUTE_OPTNONE __attribute__((optimize(0)))
#else
# define ATTRIBUTE_OPTNONE /* empty */
#endif

As you probably know, Clang defines __GNUC__ (as 4), so we would need the checks in that order. The oldest GCC version that we currently support is 4.8.5, and it does recognize the optimize attribute.