Re: Wrong order of preprocessor and compiler flags

[Evgeny Grin]

-------- Original Message --------
From: Evgeny Grin <k2k@narod.ru>
Sent: Thursday, March 24, 2022, 14:26 UTC+3
Subject: Wrong order of preprocessor and compiler flags

> > > I've found that everywhere in autoconf scripts flags are used like:
> > > $CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&AS_MESSAGE_LOG_FD
> > > while automake and libtool use flags in the other order:
> > > $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) 
> > > $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
> >
> > I agree that this should be made consistent, but before we change 
> > anything, we need to check what the rules *built into GNU and BSD 
> > Make* do with CFLAGS and CPPFLAGS (and also CXXFLAGS, OBJCFLAGS, etc) 
> > because those are much much harder to get changed than anything in 
> > Automake or Autoconf, so we should aim to harmonize everything with them.
> >
> > Can you look into that please, Evgeny?
> Yes, definitely makes sense to align with major 'make' implementations, 
> as all autotools are build to top of them.
> I'll check it.

I've made some experiments and research.
In this message, I would like to simply state the current situation.

Debian SID
---------------
Variables defined in 
https://git.savannah.gnu.org/cgit/make.git/tree/src/default.c?id=667d70eac2b5c0d7b70941574fd51a76ae93b0f4#n606
"COMPILE.c", "$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c"
"COMPILE.cc", "$(CXX) $(CXXFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c"
===============
$ LC_ALL=C make -v
GNU Make 4.3
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ touch Makefile testc.c testcpp.cc

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testc.o
cc -g0 -DNICE_MACRO  -c -o testc.o testc.c

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testcpp.o
g++ -g1 -DNICE_MACRO  -c -o testcpp.o testcpp.cc
===============


FreeBSD 13.0.
---------------
Suffixes defined in /usr/share/mk/bsd.suffixes.mk:
.c.o:
        ${CC} ${STATIC_CFLAGS} ${CFLAGS} -c ${.IMPSRC} -o ${.TARGET}
        ${CTFCONVERT_CMD}
.cc.o .cpp.o .cxx.o .C.o:
        ${CXX} ${STATIC_CXXFLAGS} ${CXXFLAGS} -c ${.IMPSRC} -o ${.TARGET}
===============
$ make -V MAKE_VERSION
20210110

$ touch Makefile testc.c testcpp.cc

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testc.o
cc  -g0 -c testc.c -o testc.o

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testcpp.o
c++  -g1 -c testcpp.cc -o testcpp.o
===============


OpenBSD 7.0
---------------
Variables defined in /usr/share/mk/sys.mk:
COMPILE.c?=     ${CC} ${CFLAGS} ${CPPFLAGS} -c
COMPILE.cc?=    ${CXX} ${CXXFLAGS} ${CPPFLAGS} -c
===============
$ touch Makefile testc.c testcpp.cc

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testc.o
cc -g0 -DNICE_MACRO -c testc.c

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testcpp.o
c++ -g1 -DNICE_MACRO -c testcpp.cc
===============


NetBSD 9
---------------
Variables defined in /usr/share/mk/sys.mk:
COMPILE.c?=     ${CC} ${CFLAGS} ${DTRACE_OPTS} ${CPPFLAGS} -c
COMPILE.cc?=    ${CXX} ${_CXXSEED} ${CXXFLAGS} ${DTRACE_OPTS} ${CPPFLAGS} -c
===============
$ touch Makefile testc.c testcpp.cc

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testc.o
cc -g0  -DNICE_MACRO -c testc.c

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testcpp.o
c++  -g1  -DNICE_MACRO -c testcpp.cc
===============


Solaris 11.4
---------------
Variables defined in /usr/share/lib/make/make.rules:
COMPILE.c=$(CC) $(CFLAGS) $(CPPFLAGS) -c
COMPILE.cc=$(CCC) $(CCFLAGS) $(CPPFLAGS)  -c
===============
$ touch Makefile testc.c testcpp.cc

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testc.o
cc -g0 -DNICE_MACRO -c  testc.c
"testc.c", line 1: warning: empty translation unit

$ make CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 CCFLAGS=-g2 testcpp.o
CC -g2 -DNICE_MACRO  -c  testcpp.cc

$ rm -f *.o

$ dmake --version
dmake: Studio 12.6 Distributed Make 8.4 SunOS_x64 2017/05/30

$ dmake -m serial CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 
CCFLAGS=-g2 testc.o
cc -g0 -DNICE_MACRO -c  testc.c
"testc.c", line 1: warning: empty translation unit

$ dmake -m serial CPPFLAGS=-DNICE_MACRO CFLAGS=-g0 CXXFLAGS=-g1 
CCFLAGS=-g2 testcpp.o
CC -g2 -DNICE_MACRO  -c  testcpp.cc
===============


Conclusions:
* All checked "make" implementations, except FreeBSD's "make", use 
"${CFLAGS} ${CPPFLAGS}";
* FreeBSD's "make" doesn't use CPPFLAGS at all
* No checked "make" implementation uses CPPFLAGS before CFLAGS

Looks like FreeBSD follows POSIX which has nothing about CPPFLAGS:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/make.html#tag_20_76_13_09

--
Evgeny

PS Sorry for crossposting. Let's more this discussion to the 
autoconf@gnu.org list.

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