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Re: Conditionally set CXXFLAGS based on directory via 1

From: Eric Blake
Subject: Re: Conditionally set CXXFLAGS based on directory via 1
Date: Wed, 27 Jul 2011 17:01:07 -0600
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On 07/27/2011 04:13 PM, Xochitl Lunde wrote:
Is there a nice way to conditionally add -fno-exceptions to CXXFLAGS for the "Source Dir" 
from or elsewhere?  I am sure I can go to each library under "Source Dir" 
and put -fno-exceptions in AM_CXXFLAGS, but is there a correct way to do it in

The nicest way to to this is to not change CXXFLAGS, but to instead AC_SUBST two different variables for the difference in which compiler options you want (you _did_ test that $CXX supports -fno-exceptions before blindly adding it to CXXFLAGS, right? Not all the world is g++). Then, in the appropriate files, modify AM_CXXFLAGS to include the appropriate substituted variables.

See how coreutils does things: in the top level, it does an AC_SUBST of WERROR_CFLAGS, WARN_CFLAGS, and GNULIB_WARN_CFLAGS - three distinct subsets of flags that were all tested on whether they were supported by the current compiler, and where WERROR_CFLAGS is conditional on whether you requested configure --enable-gcc-warnings. Then, src/ sets AM_CFLAGS to $(WARN_CFLAGS) $(WERROR_CFLAGS), while lib/ uses the less-strict AM_CFLAGS += $(GNULIB_WARN_CFLAGS) $(WERROR_CFLAGS).

Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library

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