bug#32773: [PATCH] Fix clang libstdc++ header location search

[Mathieu Othacehe]

> I think adding gcc-toolchain to propagated-inputs should work in
> principle, other than the fact that the gcc used for gcc-lib and
> libstdc++ need to be the same as the propagated gcc-toolchain. I did
> have a fix for this but I'm not sure if it's the best way of writing
> it.
> I'll send another patch with the fix though so at least others can
> comment on it!

Yes propagating gcc-toolchain would work but, would also cause gcc to be
available as a side effect. Maybe the patch attached, on top of yours,
would work?

Thanks,

Mathieu

>From ea662ff1ed62183ae0036242f53a14bb0889cb47 Mon Sep 17 00:00:00 2001
From: Mathieu Othacehe <address@hidden>
Date: Thu, 14 Nov 2019 13:25:00 +0100
Subject: [PATCH] gnu: Add clang-toolchain.

* gnu/packages/llvm.scm (make-clang-toolchain): New method.
(clang-toolchain): New public variable defined using previous method.
---
 gnu/packages/llvm.scm | 50 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/gnu/packages/llvm.scm b/gnu/packages/llvm.scm
index 0a7efe980f..8c47b884ae 100644
--- a/gnu/packages/llvm.scm
+++ b/gnu/packages/llvm.scm
@@ -37,7 +37,9 @@
   #:use-module (guix build-system cmake)
   #:use-module (guix build-system emacs)
   #:use-module (guix build-system python)
+  #:use-module (guix build-system trivial)
   #:use-module (gnu packages)
+  #:use-module (gnu packages base)
   #:use-module (gnu packages gcc)
   #:use-module (gnu packages bootstrap)           ;glibc-dynamic-linker
   #:use-module (gnu packages compression)
@@ -295,6 +297,51 @@ project includes the Clang front end, the Clang static 
analyzer, and several
 code analysis tools.")
     (license license:ncsa)))
 
+(define (make-clang-toolchain clang)
+  (package
+    (name (string-append (package-name clang) "-toolchain"))
+    (version (package-version clang))
+    (source #f)
+    (build-system trivial-build-system)
+    (arguments
+     '(#:modules ((guix build union))
+       #:builder (begin
+                   (use-modules (ice-9 match)
+                                (srfi srfi-26)
+                                (guix build union))
+
+                   (let ((out (assoc-ref %outputs "out")))
+
+                     (match %build-inputs
+                       (((names . directories) ...)
+                        (union-build out directories)))
+
+                     (union-build (assoc-ref %outputs "debug")
+                                  (list (assoc-ref %build-inputs
+                                                   "libc-debug")))
+                     (union-build (assoc-ref %outputs "static")
+                                  (list (assoc-ref %build-inputs
+                                                   "libc-static")))
+                     #t))))
+
+    (native-search-paths (package-native-search-paths clang))
+    (search-paths (package-search-paths clang))
+
+    (license (package-license clang))
+    (home-page "https://clang.llvm.org";)
+    (synopsis "Complete Clang toolchain for C/C++ development")
+    (description "This package provides a complete Clang toolchain for C/C++
+development to be installed in user profiles.  This includes Clang, as well as
+libc (headers and binaries, plus debugging symbols in the @code{debug}
+output), and Binutils.")
+    (outputs '("out" "debug" "static"))
+    (inputs `(("clang" ,clang)
+              ("ld-wrapper" ,(car (assoc-ref (%final-inputs) "ld-wrapper")))
+              ("binutils" ,binutils)
+              ("libc" ,glibc)
+              ("libc-debug" ,glibc "debug")
+              ("libc-static" ,glibc "static")))))
+
 (define-public libcxx
   (package
     (name "libcxx")
@@ -404,6 +451,9 @@ with that of libgomp, the GNU Offloading and Multi 
Processing Library.")
                    "0svk1f70hvpwrjp6x5i9kqwrqwxnmcrw5s7f4cxyd100mdd12k08"
                    #:patches '("clang-7.0-libc-search-path.patch")))
 
+(define-public clang-toolchain
+  (make-clang-toolchain clang))
+
 (define-public llvm-7
   (package
     (inherit llvm)
-- 
2.24.0