gdb/921: Makefile.in rewrites .c.o target to ignore CPPFLAGS (multiple)

[starksb at ebi dot ac dot uk]

>Number:         921
>Category:       gdb
>Synopsis:       Makefile.in rewrites .c.o target to ignore CPPFLAGS (multiple)
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 10 06:58:02 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     David Starks-Browning
>Release:        5.3 (and many previous)
>Organization:
>Environment:
One that uses libraries and include files in custom location, specified with environment variables:

LDFLAGS=-L/my/local/lib
CPPFLAGS=-I/my/local/include
>Description:
gdb/Makefile.in rewrites the .c.o default rule to ignore CPPFLAGS.  In fact this happens in a great many Makefile.in files throughout the distribution.

The standard default rule is basically:

.c.o:
         $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $<

The offending Makefile.in files override it thus:

# Prevent Sun make from putting in the machine type.  Setting
# TARGET_ARCH to nothing works for SunOS 3, 4.0, but not for 4.1.
.c.o:
	${CC} -c ${INTERNAL_CFLAGS} $<

where

INTERNAL_CFLAGS =  $(WARN_CFLAGS) ${CFLAGS} ${GLOBAL_CFLAGS} ${PROFILE_CFLAGS} ${INCLUDE_CFLAGS} ${BFD_CFLAGS}

This causes problems because ./configure will use the standard default rule and honor CPPFLAGS, and will set the appropriate HAVE_WHATEVER_H flag in configure.in.  But during make, the .h files cannot be found, because CPPFLAGS is lost.
>How-To-Repeat:
NB it is also necessary to uncomment empty LDFLAGS definition in top-level Makefile.in, otherwise empty definition overrides environment variable.
>Fix:
Modify offending Makefile.in files to look like this instead:

.c.o:
	${CC} -c ${INTERNAL_CFLAGS} $(CPPFLAGS) $<

Also remove empty "LDFLAGS =" from toplevel Makefile.in.
>Release-Note:
>Audit-Trail:
>Unformatted: