I have a need to force three files to not be optimized. I've followed the instructions in the manual for setting them up in their own library, and then using LIBADD to combine it with the original library.
If I use AM_CXXFLAGS, the -O0 is superceded by a -O2. The same occurs if I use libx_la_CXXFLAGS. I am not allowed to override CXXFLAGS (and don't want to). Makefile.am <http://Makefile.am> sample (one or the other): - libx_la_CXXFLAGS = -O0 - AM_CXXFLAGS = -O0 Resultant commands: - g++ [...] -O0 -g -O2 - /bin/sh ../../libtool --tag=CXX --mode=link g++ -O0 -g -O2 -o [...] Here's the relevant libtool rules in the generated makefile: - CXXFLAGS = -g -O2 - LTCXXCOMPILE = $(LIBTOOL) --tag=CXX --mode=compile $(CXX) $(DEFS) \ $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) \ $(AM_CXXFLAGS) $(CXXFLAGS) - .cpp.lo: if $(LTCXXCOMPILE) -MT $@ -MD -MP -MF "$(DEPDIR)/$*.Tpo" -c -o $@ $<; \ then mv -f "$(DEPDIR)/$*.Tpo" "$(DEPDIR)/$*.Plo"; else rm -f "$(DEPDIR)/$*.Tpo"; exit 1; fi As you can see, CXXFLAGS comes dead last in line in the variables, and I am never allowed to override that. I have copied the relevant section of the manual below for reference. Thanks for your comments. Brian Mingus 26.7 Per-Object Flags Emulation One of my source files needs to be compiled with different flags. How do I do? Automake supports per-program and per-library compilation flags (see Program and Library Variables<http://sources.redhat.com/automake/automake.html#Program-and-Library-Variables>and Flag Variables Ordering<http://sources.redhat.com/automake/automake.html#Flag-Variables-Ordering>). With this you can define compilation flags that apply to all files compiled for a target. For instance, in bin_PROGRAMS = foo foo_SOURCES = foo.c foo.h bar.c bar.h main.c foo_CFLAGS = -some -flags foo-foo.o, foo-bar.o, and foo-main.o will all be compiled with -some -flags. (If you wonder about the names of these object files, see renamed objects<http://sources.redhat.com/automake/automake.html#renamed-objects>.) Note that foo_CFLAGS gives the flags to use when compiling all the C sources of the *program* foo, it has nothing to do with foo.c or foo-foo.ospecifically. What if foo.c needs to be compiled into foo.o using some specific flags, that none of the other files require? Obviously per-program flags are not directly applicable here. Something like per-object flags are expected, i.e., flags that would be used only when creating foo-foo.o. Automake does not support that, however this is easy to simulate using a library that contains only that object, and compiling this library with per-library flags. bin_PROGRAMS = foo foo_SOURCES = bar.c bar.h main.c foo_CFLAGS = -some -flags foo_LDADD = libfoo.a noinst_LIBRARIES = libfoo.a libfoo_a_SOURCES = foo.c foo.h libfoo_a_CFLAGS = -some -other -flags Here foo-bar.o and foo-main.o will all be compiled with -some -flags, while libfoo_a-foo.o will be compiled using -some -other -flags. Eventually, all three objects will be linked to form foo. This trick can also be achieved using Libtool convenience libraries, for instance noinst_LTLIBRARIES = libfoo.la <http://libfoo.la> (see Libtool Convenience Libraries<http://sources.redhat.com/automake/automake.html#Libtool-Convenience-Libraries>). Another tempting idea to implement per-object flags is to override the compile rules automake would output for these files. Automake will not define a rule for a target you have defined, so you could think about defining the foo-foo.o: foo.c rule yourself. We recommend against this, because this is error prone. For instance, if you add such a rule to the first example, it will break the day you decide to remove foo_CFLAGS(because foo.c will then be compiled as foo.o instead of foo-foo.o, see renamed objects <http://sources.redhat.com/automake/automake.html#renamed-objects>). Also in order to support dependency tracking, the two .o/.obj extensions, and all the other flags variables involved in a compilation, you will end up modifying a copy of the rule previously output by automake for this file. If a new release of Automake generates a different rule, your copy will need to be updated by hand.
