Per-source CFLAGS

[Bruce Evans]

On Sat, 21 Jun 2003, David Schultz wrote:

> The following patch adds support for per-file CFLAGS, which gets
> appended to the command line after the global CFLAGS.  I would
> ...
> I intend to use this feature for gdtoa, which is technically part
> of libc, but also on a vendor branch and intended to stay that
> way.  The problem being addressed is that gcc at higher warning
> levels has some inane warnings that the vendor and I consider
> wrong, and yet people want to be able to compile libc cleanly at
> these warning levels.  As an example, gcc complains that the
> expression 'a << b - c' must have parentheses because obviously
> nobody remembers C's precedence rules.  So here's just one
> potential use of the new feature:

For this, you really want per-file WARNS, since among other reasons
compiler-dependent flags shouldn't be put in individual Makefiles.

> Index: lib/libc/gdtoa/Makefile.inc
> ===================================================================
> RCS file: /cvs/src/lib/libc/gdtoa/Makefile.inc,v
> retrieving revision 1.3
> diff -u -r1.3 Makefile.inc
> --- lib/libc/gdtoa/Makefile.inc	5 Apr 2003 22:10:13 -0000	1.3
> +++ lib/libc/gdtoa/Makefile.inc	2 May 2003 09:31:15 -0000
> @@ -16,6 +16,7 @@
>  .for src in ${GDTOASRCS}
>  MISRCS+=gdtoa_${src}
>  CLEANFILES+=gdtoa_${src}
> +CFLAGS_gdtoa_${src}+=-w

Do you need to turn off all warnings or just ones for non-broken
precedence and a few other non-broken things?  gcc doesn't give
enough control over individual warnings, but it has -Wno-parentheses
for turning off not much more than bogus warnings about natural
precedence.

> The patch I would actually like reviewed is this one:
> ...
> Index: share/mk/sys.mk
> ===================================================================
> RCS file: /cvs/src/share/mk/sys.mk,v
> retrieving revision 1.67
> diff -u -r1.67 sys.mk
> --- share/mk/sys.mk	1 Jun 2003 22:13:45 -0000	1.67
> +++ share/mk/sys.mk	21 Jun 2003 08:56:15 -0000
> ...
> @@ -117,7 +117,8 @@
>
>  # SINGLE SUFFIX RULES
>  .c:
> -	${CC} ${CFLAGS} ${LDFLAGS} -o ${.TARGET} ${.IMPSRC}
> +	${CC} ${CFLAGS} ${CFLAGS_${.IMPSRC}} ${LDFLAGS} \
> +	    -o ${.TARGET} ${.IMPSRC}
> ...

Some rules are specified by POSIX, so they can't be changed.  I don't
see how ${CFLAGS} can be per-file directly, so the POSIX spec seems to
be actively opposed to per-file CFLAGS.

Bruce