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

[M.-A. Lemburg]

Brett Cannon wrote:
> On Sun, Jun 27, 2010 at 13:37, Jeffrey Yasskin <jyasskin at gmail.com> wrote:
>> 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).

Please see the discussion on the ticket for details.

AC_PROG_CC provides the basic defaults for the CFLAGS compiler
settings depending on which compiler is chosen/found:

http://www.gnu.org/software/hello/manual/autoconf/C-Compiler.html

> I went ahead and reverted the change, but it does seem like the build
> environment could use a cleanup.

Thanks and, indeed, the build system environment variable usage does
need a cleanup. It's a larger project, though, and one that will likely
break existing build setups.

-- 
Marc-Andre Lemburg
eGenix.com

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