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Re: how to adjust default CFLAGS="-g -O2"?
From: |
Ralf Wildenhues |
Subject: |
Re: how to adjust default CFLAGS="-g -O2"? |
Date: |
Thu, 21 Aug 2008 22:42:18 +0200 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
Hello,
* Eric Blake wrote on Thu, Aug 07, 2008 at 03:20:53AM CEST:
> According to Bruno Haible on 8/6/2008 4:41 PM:
> | Could this be made customizable somehow? Either through a variable that the
> | developer could set in his configure.ac before the invocation of AC_PROG_CC,
> | or through a macro which he could redefine in his configure.ac?
>
> Hmm. This is an interesting request, and seems doable. I think it would
> be reasonable to see this in the user's configure.ac, just prior to
> AC_PROG_CC:
>
> AC_PROG_GCC_DEFAULT_FLAGS([-O2 -g -Wall])
> at which point, that string becomes the first set of CFLAGS tried for the
> compiler (if $CFLAGS is undefined), before falling back on "-g -O2" if it
> didn't work.
Oh, the ugliness of checking compiler flags.
One interesting aspect of implementing this is that the next GCC version
will ignore and may warn but will not fail upon unknown -Wno-* flags. [1]
Coping with this nicely in such a test isn't exactly trivial; as first
approximation, one could just ignore that issue. Of course, there are
other compilers that even ignore all kinds of unknown switches (but do
warn about them).
> Anyone care to contribute a patch, even if only to add a line in the TODO
> file pointing to this thread?
I've pushed the patch below.
Cheers,
Ralf
[1] <http://thread.gmane.org/gmane.comp.gcc.patches/164070/focus=164077>
2008-08-21 Ralf Wildenhues <address@hidden>
* TODO: Add item for compiler default flags.
Suggested by Bruno Haible.
diff --git a/TODO b/TODO
index 6993dce..368268c 100644
--- a/TODO
+++ b/TODO
@@ -42,6 +42,10 @@ even if they are slightly incompatible with C99. The basic
idea here
is that AC_PROG_CC should disable pedanticisms and should enable
extensions.
+Have a way to specify different default flags to try; see this thread
+for more information:
+<http://lists.gnu.org/archive/html/bug-autoconf/2008-08/msg00009.html>.
+
* Later