Re: Per-source CFLAGS

From: Bruce Evans (bde_at_zeta.org.au)
Date: 06/22/03

  • Next message: David Schultz: "Re: Per-source CFLAGS" 
    Date: Sun, 22 Jun 2003 12:07:58 +1000 (EST)
To: David Schultz <dschultz@OCF.Berkeley.EDU>

    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
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