Include file search path

[Dimitry Andric]

On 2011-03-29 23:20, mdf at FreeBSD.org wrote:
> So here's what I'm pondering.  When I build a library, like e.g. libc,
> where do the include files get pulled from?  They can't (shouldn't) be
> the ones in /usr/include, but I don't see a -nostdinc like for the
> kernel.  There are -I directives in the Makefile for
> -I${.CURDIR}/include -I${.CURDIR}/../../include, etc., but that won't
> remove /usr/include from the search path.

During the bootstrap stage, a copy of gcc (or clang) is built, that has
all default search paths for headers, libraries, etc, set relative to
${WORLDTMP}, usually /usr/obj/usr/src/tmp.

E.g:

$ /usr/obj/usr/src/tmp/usr/bin/gcc -v -E -x c /dev/null -o /dev/null
Using built-in specs.
Target: amd64-undermydesk-freebsd
Configured with: FreeBSD/amd64 system compiler
Thread model: posix
gcc version 4.2.1 20070719  [FreeBSD]
  /usr/obj/usr/src/tmp/usr/libexec/cc1 -E -quiet -v -D_LONGLONG /dev/null -o /dev/null
#include "..." search starts here:
#include <...> search starts here:
  /usr/obj/usr/src/tmp/usr/include/gcc/4.2
  /usr/obj/usr/src/tmp/usr/include
End of search list.

and:

$ /usr/obj/usr/src/tmp/usr/bin/gcc -print-search-dirs
install: /usr/obj/usr/src/tmp/usr/libexec/
programs: =/usr/obj/usr/src/tmp/usr/bin/:/usr/obj/usr/src/tmp/usr/bin/:/usr/obj/usr/src/tmp/usr/libexec/:/usr/obj/usr/src/tmp/usr/libexec/:/usr/obj/usr/src/tmp/usr/libexec/
libraries: =/usr/obj/usr/src/tmp/usr/lib/:/usr/obj/usr/src/tmp/usr/lib/

This is a rather nasty hack, though.  If we can make it work, we should
probably try using --sysroot instead, or alternatively, -nostdinc and
adding include dirs by hand.  The same for executable and library search
paths, although I am not sure if there is a way to completely reset
those with the current options.