FreeBSD port (37): avoiding dependencies towards /usr/include

[Bruno Haible]

On FreeBSD, configure is called without --with-headers option. Currently,
this has the effect that many .o files are built against /usr/include/limits.h.
Why? Any #include <limits.h>
includes                     glibc-xxxx/include/limits.h
which does #include_next     gcc-3.2's private include/limits.h
which does #include_next     /usr/include/limits.h.

You can see this by doing "grep /usr/include builddir/*/*.d".

This has two negative effects:
- During "make", a wrong limits.h is used,
- During "make install", since limits.h is one of the first few files to
  be installed, 40% of glibc files are rebuilt, which increases the
  "make install" time from 5 min. to 20 minutes.

Here is a fix.


2002-09-04  Bruno Haible  <bruno@clisp.org>

	* configure.in (SYSINCLUDES): When --with-headers is not given,
	exclude gcc's standard include dir from the include search path.

diff -r -c3 glibc-20020828.bak/configure.in glibc-20020828/configure.in
*** glibc-20020828.bak/configure.in	Wed Aug 28 21:41:55 2002
--- glibc-20020828/configure.in	Wed Sep  4 23:43:46 2002
***************
*** 635,643 ****
  # if using special system headers, find out the compiler's sekrit
  # header directory and add that to the list.  NOTE: Only does the right
  # thing on a system that doesn't need fixincludes.  (Not presently a problem.)
  if test -n "$sysheaders"; then
-   ccheaders=`$CC -print-file-name=include`
    SYSINCLUDES="-nostdinc -isystem $ccheaders -isystem $sysheaders"
  fi
  AC_SUBST(SYSINCLUDES)
  
--- 635,645 ----
  # if using special system headers, find out the compiler's sekrit
  # header directory and add that to the list.  NOTE: Only does the right
  # thing on a system that doesn't need fixincludes.  (Not presently a problem.)
+ ccheaders=`$CC -print-file-name=include`
  if test -n "$sysheaders"; then
    SYSINCLUDES="-nostdinc -isystem $ccheaders -isystem $sysheaders"
+ else
+   SYSINCLUDES="-nostdinc -isystem $ccheaders"
  fi
  AC_SUBST(SYSINCLUDES)