From 2d8aa104aaf9a2e229e31d13f6cdabf57a2e2e9a Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Wed, 4 Oct 2023 23:11:03 -0400
Subject: [PATCH] search-paths: Add GCC search paths.

* guix/search-paths.scm ($C_INCLUDE_PATH, $CPLUS_INCLUDE_PATH)
($LIBRARY_PATH, %gcc-search-paths): New variables.
---
 guix/search-paths.scm | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/guix/search-paths.scm b/guix/search-paths.scm
index 8dc81861c9..5375fae34b 100644
--- a/guix/search-paths.scm
+++ b/guix/search-paths.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014, 2015, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2022 Maxime Devos <maximedevos@telenet.be>
+;;; Copyright © 2023 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -32,13 +33,18 @@
             search-path-specification-file-type
             search-path-specification-file-pattern
 
-            $PATH
+            $CPLUS_INCLUDE_PATH
+            $C_INCLUDE_PATH
+            $LIBRARY_PATH
             $GUIX_EXTENSIONS_PATH
+            $PATH
             $PKG_CONFIG_PATH
             $SSL_CERT_DIR
             $SSL_CERT_FILE
             $TZDIR
 
+            %gcc-search-paths
+
             search-path-specification->sexp
             sexp->search-path-specification
             string-tokenize*
@@ -69,6 +75,33 @@
   (file-pattern search-path-specification-file-pattern ;#f | string
                 (default #f)))
 
+(define $C_INCLUDE_PATH
+  (search-path-specification
+   (variable "CPLUS_INCLUDE_PATH")
+   ;; Add 'include/c++' here so that <cstdlib>'s "#include_next
+   ;; <stdlib.h>" finds GCC's <stdlib.h>, not libc's.
+   (files '("include/c++" "include"))))
+
+(define $CPLUS_INCLUDE_PATH
+  (search-path-specification
+   (variable "C_INCLUDE_PATH")
+   (files '("include"))))
+
+(define $LIBRARY_PATH
+  (search-path-specification
+   (variable "LIBRARY_PATH")
+   (files '("lib" "lib64"))))
+
+(define %gcc-search-paths
+  ;; Use the language-specific variables rather than 'CPATH' because they
+  ;; are equivalent to '-isystem' whereas 'CPATH' is equivalent to '-I'.
+  ;; The intent is to allow headers that are in the search path to be
+  ;; treated as "system headers" (headers exempt from warnings) just like
+  ;; the typical /usr/include headers on an FHS system.
+  (list $C_INCLUDE_PATH
+        $CPLUS_INCLUDE_PATH
+        $LIBRARY_PATH))
+
 (define $PATH
   ;; The 'PATH' variable.  This variable is a bit special: it is not attached
   ;; to any package in particular.