Subject: [bug#32953] [PATCH core-updates-next 0/8] Use GCC7 as the default compiler.

From: Ricardo Wurmus <[email-masked]>
Date: Wed, 06 Feb 2019 23:35:24 +0100

Hi Marius,

> Efraim Flashner <[email-masked]> writes:
>
>> On Sat, Jan 19, 2019 at 07:09:04PM +0200, Efraim Flashner wrote:
>>> 
>>> I'm going to see if I can build hello --target=arm-linux-gnueabihf next
>>> and see how that works.
>>
>> When I get to gcc-cross-arm-linux-gnueabihf it fails during configure,
>> cannot find gmp.h. Looking at (gnu packages cross-base), I don't think
>> there are any package-inputs for xgcc. I still thought gcc bundled its
>> own gmp et. al.
>
> I'm happy to report that the cross-compilation issues are resolved with
> this trivial patch:
>
> 2 files changed, 5 insertions(+), 11 deletions(-)
> gnu/build/cross-toolchain.scm | 9 +++------
> gnu/packages/cross-base.scm   | 7 ++-----
>
> modified   gnu/build/cross-toolchain.scm
> @@ -36,11 +36,8 @@
>  
>  (define %gcc-include-paths
>    ;; Environment variables for header search paths.
> -  ;; Note: See <http://bugs.gnu.org/22186> for why not 'CPATH'.
> -  '("C_INCLUDE_PATH"
> -    "CPLUS_INCLUDE_PATH"
> -    "OBJC_INCLUDE_PATH"
> -    "OBJCPLUS_INCLUDE_PATH"))
> +  ;; Note: See <http://bugs.gnu.org/30756> for why not 'C_INCLUDE_PATH' & co.
> +  '("CPATH"))
>  
>  (define %gcc-cross-include-paths
>    ;; Search path for target headers when cross-compiling.
> @@ -179,7 +176,7 @@ a target triplet."
>              ;; header" such that #include_next does the right thing.
>              (for-each (lambda (var)
>                          (setenv var (string-append libc "/include")))
> -                      '("C_INCLUDE_PATH" "CPLUS_INCLUDE_PATH")))
> +                      '("CROSS_C_INCLUDE_PATH" "CROSS_CPLUS_INCLUDE_PATH")))
>            #t)))
>      (add-after 'install 'make-cross-binutils-visible
>        (cut make-cross-binutils-visible #:target target <...>))
> modified   gnu/packages/cross-base.scm
> @@ -51,11 +51,8 @@
>  
>  (define %gcc-include-paths
>    ;; Environment variables for header search paths.
> -  ;; Note: See <http://bugs.gnu.org/22186> for why not 'CPATH'.
> -  '("C_INCLUDE_PATH"
> -    "CPLUS_INCLUDE_PATH"
> -    "OBJC_INCLUDE_PATH"
> -    "OBJCPLUS_INCLUDE_PATH"))
> +  ;; Note: See <http://bugs.gnu.org/30756> for why not 'C_INCLUDE_PATH' & co.
> +  '("CPATH"))
>  
>  (define %gcc-cross-include-paths
>    ;; Search path for target headers when cross-compiling.
>
> [back]
> Silly me for not catching the CROSS_C_INCLUDE_PATH issue earlier.  But,
> at least I got to know the GCC build processes and GDB better...  ;-)
>
> I will commit this series shortly and work on a followup patch that
> removes the various GCC5/C++14 workarounds in one go.

Will this break compilation with GCC5 and older, when they are installed
in a profile or used as inputs?  Do we need copies of these variables
and use different variants for different compiler versions?

-- 
Ricardo