[Python-Dev] what environment variable should contain compiler warning suppression flags?

[Jeffrey Yasskin]

On Sun, Jun 27, 2010 at 1:04 PM, Mark Dickinson <dickinsm at gmail.com> wrote:
> On Sun, Jun 27, 2010 at 6:46 AM, Jeffrey Yasskin <jyasskin at gmail.com> wrote:
>> AC_PROG_CC is the macro that sets CFLAGS to -g -O2 on gcc-based
>> systems (http://www.gnu.org/software/hello/manual/autoconf/C-Compiler.html#index-AC_005fPROG_005fCC-842).
>> If Python's configure.in sets an otherwise-empty CFLAGS to -g before
>> calling AC_PROG_CC, AC_PROG_CC won't change it. Or we could just
>> preserve the users CFLAGS setting across AC_PROG_CC regardless of
>> whether it's set, to let the user set CFLAGS on the configure line
>> without stomping any defaults.
>
> I think saving and restoring CFLAGS across AC_PROG_CC was attempted in
> http://bugs.python.org/issue8211 . It turned out that it broke OS X
> universal builds.

Thanks for the link to the issue. http://bugs.python.org/issue8366
says Ronald Oussoren fixed the universal builds without reverting the
CFLAGS propagation.

> I'm not sure I understand the importance of allowing AC_PROG_CC to set
> CFLAGS (if CFLAGS is undefined at the point of the AC_PROG_CC);  can
> someone give an example of why this is necessary?

Marc-Andre's argument seems to be "it's possible that AC_PROG_CC adds
other flags as well (it currently doesn't, but that may well change in
future versions of autoconf)." That seems a little weak to constrain
fixing actual problems today. If it ever adds more arguments, we'll
need to inspect them anyway to see if they're more like -g or -O2
(wanted or harmful).

Jeffrey