build-system/meson: Support cross-compilation.

For cross-compilation, meson needs to be passed a
‘cross file’ with information on the architecture,
CPU type, endianness and operating system, and the
name of the cross-compiler binaries.

The new module (guix build meson-configuration) has
some utilities for writing these cross files, used
by 'make-cross-file' in a G-exp.  The values for
the cross file are generated by 'make-machine-alist'
and 'make-binaries-alist'.

'make-machine-alist' and 'make-binaries-alist' live
on the host side, such that new architectures and operating
systems can be added without causing rebuilds for old
architectures.

All operating systems and targets supported by Guix are
theoretically supported, but only aarch64-linux-gnu,
powerpc64le-linux-gnu and arm-linux-gnueabihf have been
tested.  i686-linux-gnu has also been tested with a previous
version of this patch series but required some changes
to 'cross-base.scm'.

This has been tested with:

$ ./pre-inst-env guix build glib --target=TARGET

* guix/build/meson-configuration.scm
  (write-section-header): New procedure.
  (write-assignment): New procedure.
  (write-assignments): New procedure.
* guix/build-system/meson.scm
  (target-hurd?): New predicate.
  (make-machine-alist): New procedure.
  (make-binaries-alist): New procedure.
  (make-cross-file): New procedure.
  (meson-cross-build): New procedure.
  (lower)[build-inputs]: Add standard cross packages when cross-compiling.
  Do not include regular 'inputs' when cross-compiling.
  (lower)[host-inputs]: Include 'inputs' when cross-compiling.
  (lower)[target-inputs]: Add cross packages when cross-compiling.
  (lower)[build]: Call 'meson-cross-build' instead of 'cross-build'
  when cross-compiling.
  (lower)[target]: Set it.
  (lower)[private-keywords]: Do not remove #:target when cross-compiling.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>

1 files changed, 190 insertions, 19 deletions

diff --git a/guix/build-system/meson.scm b/guix/build-system/meson.scm
index 5adc0f92c8..dae0abde94 100644
--- a/guix/build-system/meson.scm
+++ b/guix/build-system/meson.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2017 Peter Mikkelsen <petermikkelsen10@gmail.com>
 ;;; Copyright © 2018, 2019 Marius Bakke <mbakke@fastmail.com>
 ;;; Copyright © 2021 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -30,7 +31,8 @@
   #:use-module (guix packages)
   #:use-module (ice-9 match)
   #:export (%meson-build-system-modules
-            meson-build-system))
+            meson-build-system
+            make-cross-file))
 
 ;; Commentary:
 ;;
@@ -40,6 +42,68 @@
 ;;
 ;; Code:
 
+(define (make-machine-alist triplet)
+  "Make an association list describing what should go into
+the ‘host_machine’ section of the cross file when cross-compiling
+for TRIPLET."
+  `((system . ,(cond ((target-hurd? triplet) "gnu")
+                     ((target-linux? triplet) "linux")
+                     ((target-mingw? triplet) "windows")
+                     (#t (error "meson: unknown operating system"))))
+    (cpu_family . ,(cond ((target-x86-32? triplet) "x86")
+                         ((target-x86-64? triplet) "x86_64")
+                         ((target-arm32? triplet) "arm")
+                         ((target-aarch64? triplet) "aarch64")
+                         ((target-powerpc? triplet)
+                          (if (target-64bit? triplet)
+                              "ppc64"
+                              "ppc"))
+                         (#t (error "meson: unknown architecture"))))
+    (cpu . ,(cond ((target-x86-32? triplet) ; i386, ..., i686
+                   (substring triplet 0 4))
+                  ((target-x86-64? triplet) "x86_64")
+                  ((target-aarch64? triplet) "armv8-a")
+                  ((target-arm32? triplet) "armv7")
+                  ;; According to #mesonbuild on OFTC, there does not appear
+                  ;; to be an official-ish list of CPU types recognised by
+                  ;; Meson, the "cpu" field is not used by Meson itself and
+                  ;; most software doesn't look at this field, except perhaps
+                  ;; for selecting optimisations, so set it to something
+                  ;; arbitrary.
+                  (#t "strawberries")))
+    (endian . ,(cond ((string-prefix? "powerpc64le-" triplet) "little")
+                     ((string-prefix? "mips64el-" triplet) "little")
+                     ((target-x86-32? triplet) "little")
+                     ((target-x86-64? triplet) "little")
+                     ;; At least in Guix.  Aarch64 and 32-bit arm
+                     ;; have a big-endian mode as well.
+                     ((target-arm? triplet) "little")
+                     (#t (error "meson: unknown architecture"))))))
+
+(define (make-binaries-alist triplet)
+  "Make an associatoin list describing what should go into
+the ‘binaries’ section of the cross file when cross-compiling for
+TRIPLET."
+  `((c . ,(cc-for-target triplet))
+    (cpp . ,(cxx-for-target triplet))
+    (pkgconfig . ,(pkg-config-for-target triplet))
+    (objcopy . ,(string-append triplet "-objcopy"))
+    (ar . ,(string-append triplet "-ar"))
+    (ld . ,(string-append triplet "-ld"))
+    (strip . ,(string-append triplet "-strip"))))
+
+(define (make-cross-file triplet)
+  (computed-file "cross-file"
+    (with-imported-modules '((guix build meson-configuration))
+      #~(begin
+          (use-modules (guix build meson-configuration))
+          (call-with-output-file #$output
+            (lambda (port)
+              (write-section-header port "host_machine")
+              (write-assignments port '#$(make-machine-alist triplet))
+              (write-section-header port "binaries")
+              (write-assignments port '#$(make-binaries-alist triplet))))))))
+
 (define %meson-build-system-modules
   ;; Build-side modules imported by default.
   `((guix build meson-build-system)
@@ -68,24 +132,34 @@
                 #:rest arguments)
   "Return a bag for NAME."
   (define private-keywords
-    `(#:meson #:ninja #:inputs #:native-inputs #:outputs #:target))
-
-  (and (not target) ;; TODO: add support for cross-compilation.
-       (bag
-         (name name)
-         (system system)
-         (build-inputs `(("meson" ,meson)
-                         ("ninja" ,ninja)
-                         ,@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)))))
+    `(#:meson #:ninja #:inputs #:native-inputs #:outputs
+      ,@(if target
+            '()
+            '(#:target))))
+
+  (bag
+    (name name)
+    (system system) (target target)
+    (build-inputs `(("meson" ,meson)
+                    ("ninja" ,ninja)
+                    ,@native-inputs
+                    ,@(if target '() inputs)
+                    ;; Keep the standard inputs of 'gnu-build-system'.
+                    ,@(if target
+                          (standard-cross-packages target 'host)
+                          '())
+                    ,@(standard-packages)))
+    (host-inputs `(,@(if source
+                         `(("source" ,source))
+                         '())
+                   ,@(if target inputs '())))
+    ;; Keep the standard inputs of 'gnu-buid-system'.
+    (target-inputs (if target
+                       (standard-cross-packages target 'target)
+                       '()))
+    (outputs outputs)
+    (build (if target meson-cross-build meson-build))
+    (arguments (strip-keyword-arguments private-keywords arguments))))
 
 (define* (meson-build name inputs
                       #:key
@@ -161,6 +235,103 @@ has a 'meson.build' file."
                       #:disallowed-references disallowed-references
                       #:guile-for-build guile)))
 
+(define* (meson-cross-build name
+                            #:key
+                            target
+                            build-inputs host-inputs target-inputs
+                            guile source
+                            (outputs '("out"))
+                            (configure-flags ''())
+                            (search-paths '())
+                            (native-search-paths '())
+
+                            (build-type "debugoptimized")
+                            (tests? #f)
+                            (test-target "test")
+                            (glib-or-gtk? #f)
+                            (parallel-build? #t)
+                            (parallel-tests? #f)
+                            (validate-runpath? #t)
+                            (patch-shebangs? #t)
+                            (strip-binaries? #t)
+                            (strip-flags ''("--strip-debug"))
+                            (strip-directories ''("lib" "lib64" "libexec"
+                                                  "bin" "sbin"))
+                            (elf-directories ''("lib" "lib64" "libexec"
+                                                "bin" "sbin"))
+                            ;; See 'gnu-cross-build' for why this needs to be
+                            ;; disabled when cross-compiling.
+                            (make-dynamic-linker-cache? #f)
+                            (phases '%standard-phases)
+                            (system (%current-system))
+                            (imported-modules %meson-build-system-modules)
+                            (modules '((guix build meson-build-system)
+                                       (guix build utils)))
+                            allowed-references
+                            disallowed-references)
+  "Cross-build SOURCE for TARGET using MESON, and with INPUTS, assuming that
+SOURCE has a 'meson.build' file."
+  (define cross-file
+    (make-cross-file target))
+  (define inputs
+    (if (null? target-inputs)
+        (input-tuples->gexp host-inputs)
+        #~(append #$(input-tuples->gexp host-inputs)
+                  #+(input-tuples->gexp target-inputs))))
+  (define builder
+    (with-imported-modules imported-modules
+      #~(begin
+          (use-modules #$@(sexp->gexp modules))
+
+          (define build-phases
+            #$(let ((phases (if (pair? phases) (sexp->gexp phases) phases)))
+                (if glib-or-gtk?
+                    phases
+                    #~(modify-phases #$phases
+                        (delete 'glib-or-gtk-compile-schemas)
+                        (delete 'glib-or-gtk-wrap)))))
+
+          ;; Do not use 'with-build-variables', as there should be
+          ;; no reason to use %build-inputs and friends.
+          (meson-build #:source #+source
+                       #:system #$system
+                       #:build #$(nix-system->gnu-triplet system)
+                       #:target #$target
+                       #:outputs #$(outputs->gexp outputs)
+                       #:inputs #$inputs
+                       #:native-inputs #+(input-tuples->gexp build-inputs)
+                       #:search-paths '#$(sexp->gexp
+                                          (map search-path-specification->sexp
+                                                     search-paths))
+                       #:native-search-paths '#$(sexp->gexp
+                                                 (map search-path-specification->sexp
+                                                      native-search-paths))
+                       #:phases build-phases
+                       #:make-dynamic-linker-cache? #$make-dynamic-linker-cache?
+                       #:configure-flags `("--cross-file" #+cross-file
+                                           ,@#$(sexp->gexp configure-flags))
+                       #:build-type #$build-type
+                       #:tests? #$tests?
+                       #:test-target #$test-target
+                       #:parallel-build? #$parallel-build?
+                       #:parallel-tests? #$parallel-tests?
+                       #:validate-runpath? #$validate-runpath?
+                       #:patch-shebangs? #$patch-shebangs?
+                       #:strip-binaries? #$strip-binaries?
+                       #:strip-flags #$(sexp->gexp strip-flags)
+                       #:strip-directories #$(sexp->gexp strip-directories)
+                       #:elf-directories #$(sexp->gexp elf-directories)))))
+
+  (mlet %store-monad ((guile (package->derivation (or guile (default-guile))
+                                                  system #:graft? #f)))
+    (gexp->derivation name builder
+                      #:system system
+                      #:target target
+                      #:substitutable? substitutable?
+                      #:allowed-references allowed-references
+                      #:disallowed-references disallowed-references
+                      #:guile-for-build guile)))
+
 (define meson-build-system
   (build-system
     (name 'meson)