gnu: gcc: Switch back to using 'C_INCLUDE_PATH' instead of 'CPATH'.

Fixes <https://bugs.gnu.org/30756>.
Initially reported by Julien Lepiller <julien@lepiller.eu>.

* gnu/packages/base.scm (make-gcc-libc): Remove
'treat-glibc-as-system-header' phase from 'arguments'.
* gnu/packages/commencement.scm (gcc-final): Likewise.
* gnu/packages/gcc.scm (gcc-4.7)[arguments]: Add "include/c++" to
'CPLUS_INCLUDE_PATH'.
(gcc-6)[native-search-paths]: Remove.
* gnu/packages/make-bootstrap.scm (gcc-for-bootstrap): Remove
'native-search-paths' and 'arguments'.
* gnu/packages/patches/python-2.7-search-paths.patch,
gnu/packages/patches/python-3-search-paths.patch: Replace "CPATH" with
"C_INCLUDE_PATH".
* guix/build-system/cmake.scm (lower): When not cross-compiling, move
INPUTS from the 'host-inputs' field to the 'build-inputs' field of the
bag, right after NATIVE-INPUTS.
* guix/build-system/glib-or-gtk.scm (lower): Likewise.
* guix/build-system/gnu.scm (lower): Likewise.
* guix/build-system/meson.scm (lower): Likewise.

4 files changed, 26 insertions, 19 deletions

diff --git a/guix/build-system/cmake.scm b/guix/build-system/cmake.scm
index 1fc0931a27..29259c5785 100644
--- a/guix/build-system/cmake.scm
+++ b/guix/build-system/cmake.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Cyril Roelandt <tipecaml@gmail.com>
 ;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;;
@@ -72,6 +72,7 @@
                           '())
                     ,@`(("cmake" ,cmake))
                     ,@native-inputs
+                    ,@(if target '() inputs)
                     ,@(if target
                           ;; Use the standard cross inputs of
                           ;; 'gnu-build-system'.
@@ -79,7 +80,7 @@
                           '())
                     ;; Keep the standard inputs of 'gnu-build-system'.
                     ,@(standard-packages)))
-    (host-inputs inputs)
+    (host-inputs (if target inputs '()))
 
     ;; The cross-libc is really a target package, but for bootstrapping
     ;; reasons, we can't put it in 'host-inputs'.  Namely, 'cross-gcc' is a
diff --git a/guix/build-system/glib-or-gtk.scm b/guix/build-system/glib-or-gtk.scm
index 8de7dfbfc2..fb1f8fb930 100644
--- a/guix/build-system/glib-or-gtk.scm
+++ b/guix/build-system/glib-or-gtk.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Cyril Roelandt <tipecaml@gmail.com>
 ;;; Copyright © 2014 Federico Beffa <beffa@fbengineering.ch>
 ;;;
@@ -92,15 +92,15 @@
        (bag
          (name name)
          (system system)
-         (host-inputs `(,@(if source
-                              `(("source" ,source))
-                              '())
-                        ,@inputs))
-         (build-inputs `(("glib:bin" ,glib "bin") ; to compile schemas
+         (host-inputs (if source
+                          `(("source" ,source))
+                          '()))
+         (build-inputs `(,@native-inputs
+                         ,@inputs
+                         ("glib:bin" ,glib "bin") ; to compile schemas
                          ,@(if implicit-inputs?
                                (standard-packages)
-                               '())
-                         ,@native-inputs))
+                               '())))
          (outputs outputs)
          (build glib-or-gtk-build)
          (arguments (strip-keyword-arguments private-keywords arguments)))))
diff --git a/guix/build-system/gnu.scm b/guix/build-system/gnu.scm
index 3cc89f8852..6e66f5ffce 100644
--- a/guix/build-system/gnu.scm
+++ b/guix/build-system/gnu.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -296,13 +296,19 @@ standard packages used as implicit inputs of the GNU build system."
                           `(("source" ,source))
                           '())
                     ,@native-inputs
+
+                    ;; When not cross-compiling, ensure implicit inputs come
+                    ;; last.  That way, libc headers come last, which allows
+                    ;; #include_next to work correctly; see
+                    ;; <https://bugs.gnu.org/30756>.
+                    ,@(if target '() inputs)
                     ,@(if (and target implicit-cross-inputs?)
                           (standard-cross-packages target 'host)
                           '())
                     ,@(if implicit-inputs?
                           (standard-packages)
                           '())))
-    (host-inputs inputs)
+    (host-inputs (if target inputs '()))
 
     ;; The cross-libc is really a target package, but for bootstrapping
     ;; reasons, we can't put it in 'host-inputs'.  Namely, 'cross-gcc' is a
diff --git a/guix/build-system/meson.scm b/guix/build-system/meson.scm
index b29f2f4ecf..b68bcb80de 100644
--- a/guix/build-system/meson.scm
+++ b/guix/build-system/meson.scm
@@ -74,13 +74,13 @@
          (system system)
          (build-inputs `(("meson" ,meson)
                          ("ninja" ,ninja)
-                         ,@native-inputs))
-         (host-inputs `(,@(if source
-                              `(("source" ,source))
-                              '())
-                        ,@inputs
-                        ;; Keep the standard inputs of 'gnu-build-system'.
-                        ,@(standard-packages)))
+                         ,@native-inputs
+                         ,@inputs
+                         ;; Keep the standard inputs of 'gnu-build-system'.
+                         ,@(standard-packages)))
+         (host-inputs (if source
+                          `(("source" ,source))
+                          '()))
          (outputs outputs)
          (build meson-build)
          (arguments (strip-keyword-arguments private-keywords arguments)))))