Hi Alex. -------- Original Message -------- From: Alex Ameen <alex.ameen.tx@xxxxxxxxx> Sent: Friday, March 25, 2022, 03:45 UTC+3 Subject: Wrong order of preprocessor and compiler flags
The rationale for placement of `CPPFLAGS` early is to allow users to better control include ordering. This is similar to why `CFLAGS` is last. Consider this situation : User wants to preempt the default include path, and wants to override the C standard. make CPPFLAGS='-Ifoo/bar' CFLAGS='-std=c18'; If `CPPFLAGS` were at the end, the user must use `-quote foo/bar` to successfully preempt which has a different meaning in some edge cases. Notably if the includes are in carrots rather than quotes it ain't gonna work.
Not sure that I got your point.
I've tested with GNU Make in empty dir (and GCC as 'cc'):
----------------
$ mkdir -p foo/bar
$ touch Makefile foo/bar/myheader.h
$ echo '#include <myheader.h>' > cincl.c
$ make CPPFLAGS='-Ifoo/bar' CFLAGS='-std=c18' cincl.o
cc -std=c18 -Ifoo/bar -c -o cincl.o cincl.c
$ echo '#include "myheader.h"' > cincl2.c
$ make CPPFLAGS='-Ifoo/bar' CFLAGS='-std=c18' cincl2.o
cc -std=c18 -Ifoo/bar -c -o cincl2.o cincl2.c
$ rm -f *.o
$ make CFLAGS='-std=c18' cincl.o
cc -std=c18 -c -o cincl.o cincl.c
cincl.c:1:10: fatal error: myheader.h: No such file or directory
1 | #include <myheader.h>
| ^~~~~~~~~~~~
compilation terminated.
make: *** [<builtin>: cincl.o] Error 1
$ make CFLAGS='-std=c18' cincl2.o
cc -std=c18 -c -o cincl2.o cincl2.c
cincl2.c:1:10: fatal error: myheader.h: No such file or directory
1 | #include "myheader.h"
| ^~~~~~~~~~~~
compilation terminated.
make: *** [<builtin>: cincl2.o] Error 1
----------------
GNU Make uses CPPFLAGS at the end of the parameters block without any
problem. It just works.
In both cases the ordering is intended to allow users to override defaults. I agree that this ordering isn't ideal for other flags like `-D`, but considering a change would break builds with existing work arounds I think any reordering is going to rouse the masses into an angry stupor.
The problem is that we already have reordering.Tests/checks are performed by 'configure' as "$CC $CFLAGS $CPPFLAGS", but result is used in automake files as "$CC $CPPFLAGS $CFLAGS".
Either autoconf or automake should be corrected.As no 'make' implementation uses CPPFLAGS before CFLAGS [1], others [2] use $CFLAGS $CPPFLAGS as well, it makes sense to correct automake to align with other tools and leave autoconf without changes.
[1] https://lists.gnu.org/archive/html/autoconf/2022-03/msg00010.html [2] https://lists.gnu.org/archive/html/autoconf/2022-03/msg00008.html -- Evgeny
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