Ping: [RFA 1/2]: Don't ignore target_header_dir when deciding inhibit_libc

[Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>]

Ping! <http://gcc.gnu.org/ml/gcc-patches/2014-09/msg00402.html>

> From: Hans-Peter Nilsson <hp@axis.com>
> Date: Thu, 4 Sep 2014 23:40:40 +0200

> The directory at $target_header_dir is already inspected in
> gcc/configure, for e.g. glibc version and stack protector
> support, but not for setting inhibit_libc.  This is just
> inconsistent and the obvious resolution to me is to inhibit
> inhibit_libc when a target *does* "have its own set of headers",
> to quote the comment above the inhibit_libc setting.  There is
> nothing in the build log for "make all-gcc" that shows a
> difference with/without --with-headers, if headers are actually
> present anyway!
> 
> It may seem that libgcc/configure.ac would be the appropriate
> place to patch and test, but it is gcc/configure.ac which tests
> various things about target headers and makes the inhibit_libc
> decision, exporting it through the generated obj/gcc/libgcc.mvars
> that is included in libgcc/Makefile.
> 
> Tested before/after by "make all-gcc" on native x86_64-linux (*a) and
> seeing it still set (for the peace of most users) in
> gcc/Makefile, and cross to mipsel-linux "make all-gcc" with/without (*b,c) a
> pre-installed set of headers just implied by --prefix and --target to
> observe the intended difference and the same with (*d)
> --with-sysroot (but no headers at the sysroot) and (*e)
> --with-build-sysroot and both (*f) (note that
> --with-build-sysroot=... without --with-sysroot also got
> inhibit_libc) to observe no change for the --with-sysroot one
> (still no inhibit_libc).  The same with --with-headers
> (*g). Also, I checked that nothing other than the inhibit_libc code
> uses target_header_dir or sets the used variables in the block
> of code involved in the move.
> 
> Ok to commit?
> 
> gcc:
> 	* configure.ac (target_header_dir): Move block defining
> 	this to before the block setting inhibit_libc.
> 	(inhibit_libc): When considering $with_headers, just
> 	check it it's explicitly "no".  If not, also check if
> 	$target_header_dir/stdio.h is present.  If not, set
> 	inhibit_libc=true.
> 	* configure: Regenerate.
> 
> Index: gcc/configure.ac
> ===================================================================
> --- gcc/configure.ac	(revision 214736)
> +++ gcc/configure.ac	(working copy)
> @@ -1924,6 +1924,22 @@ elif test "x$TARGET_SYSTEM_ROOT" != x; t
>          SYSTEM_HEADER_DIR=$build_system_header_dir 
>  fi
>  
> +if test x$host != x$target || test "x$TARGET_SYSTEM_ROOT" != x; then
> +  if test "x$with_headers" != x; then
> +    target_header_dir=$with_headers
> +  elif test "x$with_sysroot" = x; then
> +    target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-include"
> +  elif test "x$with_build_sysroot" != "x"; then
> +    target_header_dir="${with_build_sysroot}${native_system_header_dir}"
> +  elif test "x$with_sysroot" = xyes; then
> +    target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-root${native_system_header_dir}"
> +  else
> +    target_header_dir="${with_sysroot}${native_system_header_dir}"
> +  fi
> +else
> +  target_header_dir=${native_system_header_dir}
> +fi
> +
>  # If this is a cross-compiler that does not
>  # have its own set of headers then define
>  # inhibit_libc
> @@ -1935,7 +1951,7 @@ fi
>  : ${inhibit_libc=false}
>  if { { test x$host != x$target && test "x$with_sysroot" = x ; } ||
>         test x$with_newlib = xyes ; } &&
> -     { test "x$with_headers" = x || test "x$with_headers" = xno ; } ; then
> +     { test "x$with_headers" = xno || test ! -f "$target_header_dir/stdio.h"; } ; then
>         inhibit_libc=true
>  fi
>  AC_SUBST(inhibit_libc)
> @@ -4441,22 +4457,6 @@ if test x$with_sysroot = x && test x$hos
>     && test "$prefix" != "NONE"; then
>    AC_DEFINE_UNQUOTED(PREFIX_INCLUDE_DIR, "$prefix/include",
>  [Define to PREFIX/include if cpp should also search that directory.])
> -fi
> -
> -if test x$host != x$target || test "x$TARGET_SYSTEM_ROOT" != x; then
> -  if test "x$with_headers" != x; then
> -    target_header_dir=$with_headers
> -  elif test "x$with_sysroot" = x; then
> -    target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-include"
> -  elif test "x$with_build_sysroot" != "x"; then
> -    target_header_dir="${with_build_sysroot}${native_system_header_dir}"
> -  elif test "x$with_sysroot" = xyes; then
> -    target_header_dir="${test_exec_prefix}/${target_noncanonical}/sys-root${native_system_header_dir}"
> -  else
> -    target_header_dir="${with_sysroot}${native_system_header_dir}"
> -  fi
> -else
> -  target_header_dir=${native_system_header_dir}
>  fi
>  
>  # Determine the version of glibc, if any, used on the target.
> 
> brgds, H-P
>