Use AX_ADD_FORTIFY_SOURCE to avoid redefining _FORTIFY_SOURCE

[thesamesam]

Some distributions are now setting -D_FORTIFY_SOURCE=3 by default in their toolchains rather than _F_S=2. By forcing _F_S=2, this causes both a warning and a downgrade in the effective protection.

Use the autoconf-archive macro for this purpose (AX_ADD_FORTIFY_SOURCE) to add the fortification at the highest supported level if the compiler doesn't already default to it.

[legionus]

@thesamesam This seems generally correct and useful. But your change breaks distcheck:

./configure: line 17217: syntax error near unexpected token `-Werror,CFLAGS="$CFLAGS -Werror"'
checking for library containing timer_create... none required
./configure: line 17217: `    AX_CHECK_COMPILE_FLAG(-Werror,CFLAGS="$CFLAGS -Werror")'

[thesamesam]

Thanks. I can't seem to reproduce it locally yet, although I think I can see how it might happen with the -Werror mangling.

I'm going to switch to AS_IF as well given bare if is now recommended against. Let's see if that does the job...

[legionus]

I found the problem. The problem is not that -Werror is used, but that the AX_CHECK_COMPILE_FLAG macro is not expanded. We must also copy /usr/share/aclocal/ax_check_compile_flag.m4 to the m4 directory.

[thesamesam]

Thanks for the help - sorry it wasn't as straightforward as it was supposed to be.

[legionus]

Thank you! Applied.