[Bug c/54696] New: Makefile doesn't propagate CPPFLAGS properly

["noah.b.lavine at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54696

             Bug #: 54696
           Summary: Makefile doesn't propagate CPPFLAGS properly
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: noah.b.lavine@gmail.com


I tried to build GCC 4.7.2 from the source tarball, specifying a -I option in
CPPFLAGS because I keep header files in a nonstandard place
(~/.nix-profile/include).

Unfortunately, gcc failed to build. Instead it produced the error

gcc  -I../.././libcpp -I. -I../.././libcpp/../include -I../.././libcpp/include 
-g -fkeep-inline-functions -W -Wall -Wwrite-strings -Wmissing-format-attribute
-Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wc++-compat
-pedantic -Wno-long-long  -I../.././libcpp -I. -I../.././libcpp/../include
-I../.././libcpp/include  -c -o charset.o -MT charset.o -MMD -MP -MF
.deps/charset.Tpo ../.././libcpp/charset.c
In file included from ../.././libcpp/charset.c:22:0:
../.././libcpp/system.h:276:21: fatal error: libintl.h: No such file or
directory
compilation terminated.

But libintl.h exists in ~/.nix-profile/include. The problem is clear: the -I
statement from CPPFLAGS is not being used.

This particular statement is part of compiling libcpp, so I looked at the
makefile for libcpp, and found this line:

CPPFLAGS = 

This is the problem. It seems clear that what is happening is that the CPPFLAGS
that I use when I configure the main GCC executable are not being passed on to
the configuration script for libcpp, which then doesn't know where to find
libintl. When I edit the makefile by hand to set CPPFLAGS correctly, the build
gets past that point.

One odd note is that I also pass LDFLAGS, and that *is* passed on to libcpp. So
it is not that all environment variables aren't propagated.