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Use CFLAGS/CXXFLAGS related macros as soon as possible.
AC_CHECK_CC_OPT(flag, cachevarname)
AC_CHECK_CC_OPT(-fvomit-frame,vomitframe) would show a message as like "checking wether gcc accepts -fvomit-frame ... no" and sets the shell-variable $vomitframe to either "-fvomit-frame" or (in this case) just a simple "". In many cases you would then call AC_SUBST(_fvomit_frame_,$vomitframe) to create a substitution that could be fed as "CFLAGS = @_funsigned_char_@ @_fvomit_frame_@.
In consequence this function is much more general than their specific counterparts like ac_cxx_rtti.m4 that will test for -fno-rtti -fno-exceptions.
This macro will be obsolete in the very near future - there should be two macros AX_CFLAGS_OPTION and AX_CXXFLAGS_OPTION that will add directly to the CFLAGS/CXXFLAGS unless a ac_subst-variable was given. Remind me of doing so if I forget about writing it all up - to use $CC-cc directly in here instead of ac_compile macro is bad anyway.
Guido Draheim <guidod@gmx.de>
2005-01-25
AC_DEFUN([AC_CHECK_CC_OPT], [AC_CACHE_CHECK(whether ${CC-cc} accepts [$1], [$2], [AC_SUBST($2) echo 'void f(){}' > conftest.c if test -z "`${CC-cc} -c $1 conftest.c 2>&1`"; then $2="$1" else $2="" fi rm -f conftest* ])])