From 366729d477960127424076bdac51e7c937857081 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Sun, 19 Apr 2020 23:14:56 +0200
Subject: [PATCH 1/2] build-self: Always build the trampoline for the current
 system.

Previously we'd build 'compute-guix-derivation' for the target system.
Running it would then fail (unless qemu-binfmt support was set up or
something similar).

Fixes <https://bugs.gnu.org/39531>.
Reported by Christopher Baines <mail@cbaines.net>.

* build-aux/build-self.scm (load-path-expression): Add #:system and
honor it.
(gexp->script): Likewise.
(build-program): Pass #:system to 'gexp->script'.
---
 build-aux/build-self.scm | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/build-aux/build-self.scm b/build-aux/build-self.scm
index f86c79f0d0..58ecf20cf4 100644
--- a/build-aux/build-self.scm
+++ b/build-aux/build-self.scm
@@ -148,14 +148,17 @@
 ;;; 1ae16033f34cebe802023922436883867010850f (March 2018.)
 ;;;
 
-(define (load-path-expression modules path)
+(define* (load-path-expression modules path
+                               #:key (system (%current-system)))
   "Return as a monadic value a gexp that sets '%load-path' and
 '%load-compiled-path' to point to MODULES, a list of module names.  MODULES
 are searched for in PATH."
   (mlet %store-monad ((modules  (imported-modules modules
-                                                  #:module-path path))
+                                                  #:module-path path
+                                                  #:system system))
                       (compiled (compiled-modules modules
-                                                  #:module-path path)))
+                                                  #:module-path path
+                                                  #:system system)))
     (return (gexp (eval-when (expand load eval)
                     (set! %load-path
                       (cons (ungexp modules) %load-path))
@@ -165,12 +168,14 @@ are searched for in PATH."
 
 (define* (gexp->script name exp
                        #:key (guile (default-guile))
-                       (module-path %load-path))
+                       (module-path %load-path)
+                       (system (%current-system)))
   "Return an executable script NAME that runs EXP using GUILE, with EXP's
 imported modules in its search path."
   (mlet %store-monad ((set-load-path
                        (load-path-expression (gexp-modules exp)
-                                             module-path)))
+                                             module-path
+                                             #:system system)))
     (gexp->derivation name
                       (gexp
                        (call-with-output-file (ungexp output)
@@ -186,7 +191,8 @@ imported modules in its search path."
                            (write '(ungexp set-load-path) port)
                            (write '(ungexp exp) port)
                            (chmod port #o555))))
-                      #:module-path module-path)))
+                      #:module-path module-path
+                      #:system system)))
 
 
 (define (date-version-string)
@@ -364,7 +370,11 @@ interface (FFI) of Guile.")
                                                 #$pull-version)
                                #:system system)
                              derivation-file-name))))))
-                  #:module-path (list source))))
+                  #:module-path (list source)
+
+                  ;; Always build the trampoline for the local system.  The
+                  ;; system being targeted will be passed as an argument.
+                  #:system %system)))
 
 (define (call-with-clean-environment thunk)
   (let ((env (environ)))
-- 
2.26.0