On Tue, Dec 12, 2017 at 05:45:50AM -0800, Matt Wette wrote:
> The FFI Helper uses `gcc --print-search-dirs' to locate gcc directories.  It also adds /usr/include.
> I don't understand why it is not finding them.  It also uses `gcc -dM -E' to determine #defines.
> Even with that, on my macOS system, I need to make fixes.   Can you determine if some gcc 
> command, via `gcc --print-search-dirs' will find the correct includes?  Maybe I should add a 
> `--with-gcc' command line argument.
> 
> Thanks,
> Matt
> 


There are no include directories found at all by
„gcc --print-search-dirs“ on my GuixSD or Arch installation.

$ gcc --print-search-dirs
install: /gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/
programs: =/gnu/store/bhv43hzkfwcrvm2grq9fiw5bh1h5j3vc-gcc-7.2.0/libexec/gcc/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/bhv43hzkfwcrvm2grq9fiw5bh1h5j3vc-gcc-7.2.0/libexec/gcc/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/bhv43hzkfwcrvm2grq9fiw5bh1h5j3vc-gcc-7.2.0/libexec/gcc/x86_64-unknown-linux-gnu/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../../../../../x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../../../../../x86_64-unknown-linux-gnu/bin/
libraries: =/gnu/store/zrmhjw6kha4ghra2dkr06kldarxybgkw-profile/lib/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/zrmhjw6kha4ghra2dkr06kldarxybgkw-profile/lib/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../../../../../x86_64-unknown-linux-gnu/lib/x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../../../../../x86_64-unknown-linux-gnu/lib/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../x86_64-unknown-linux-gnu/7.2.0/:/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../:/gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/libx86_64-unknown-linux-gnu/7.2.0/:/gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/lib
$ gcc --print-search-dirs | grep include
$ 

It looks similar but less verbose on Arch.  On Parabola / Arch Linux
ffi-helper tried to find the 32-bit header on a 64-bit system which
was not installed.

According to https://gcc.gnu.org/ml/gcc-help/2007-09/msg00205.html
which I found with a very quick Web search one can check the output
from „cpp -Wp,-v“.

$ cpp -Wp,-v   
ignoring nonexistent directory "/no-gcc-local-prefix/include"
ignoring nonexistent directory "/gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/../../../../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /gnu/store/zrmhjw6kha4ghra2dkr06kldarxybgkw-profile/include
 /gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/include
 /gnu/store/h3z6nshhdlc8zgh4mi13x1br03xipi9r-gcc-7.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/7.2.0/include-fixed
 /gnu/store/3h31zsqxjjg52da5gp3qmhkh4x8klhah-glibc-2.25/include
End of search list.

This looks right.  However this may be fragile.  Including these
directories with the -I option as well as the path to Gettext’s
include directory allows me to compile-ffi the gettext-po.ffi file.
Except when including <stdlib.h> ffi-helper is still looking for not
installed gnu/stubs-32.h on a 64-bit system with a 64-bit glibc and
64-bit gcc.

Regards,
Florian