[bug#49880] [PATCH 1/2] gnu: gmp-boot: Fix build on powerpc64le-linux

[Thiago Jung Bauermann via Guix-patches via <guix-patches@gnu.org>]

Linux on powerpc64 used to run in big-endian mode only.  When support for
little-endian mode was added around 2014, they took the opportunity to
update the ELF ABI.  The new ABI is known as ELF ABI v2, and the old one
retroactively called ELF ABI v1.

GMP 4.3.2 was released in 2010, so its hand-optimized assembly code for
powerpc64 only support ELF ABI v1.  This causes a build failure on
powerpc64le-linux, which can be fixed by passing a host triplet with the
“none” CPU type.  This tells the configure script to use generic C code for
the build.

* gnu/packages/commencement.scm (gmp-boot)[arguments]{#:configure-flags}: Add
“--host=none-unknown-linux-gnu” for powerpc64le targets.
---

Hello,

This patch fixes the following build error on powerpc64le-linux (shown
below for one file, but happens on several):

ld: mpn/.libs/add_n.o: ABI version 1 is not compatible with ABI version 2 output
ld: failed to merge target specific data of file mpn/.libs/add_n.o

I started investigating the problem in core-udpates-frozen but the same
issue happens in master as well so I suggest comitting it there instead.
The patch applies cleanly to both branches.

Thanks,
Thiago

 gnu/packages/commencement.scm | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/commencement.scm b/gnu/packages/commencement.scm
index e7bd6cf002c7..ae3f07bc59ef 100644
--- a/gnu/packages/commencement.scm
+++ b/gnu/packages/commencement.scm
@@ -1840,7 +1840,23 @@ ac_cv_c_float_format='IEEE (little-endian)'
               (uri (string-append "mirror://gnu/gmp/gmp-" version
                                   ".tar.gz"))
               (sha256 (base32
-                       "15rwq54fi3s11izas6g985y9jklm3xprfsmym3v1g6xr84bavqvv"))))))
+                       "15rwq54fi3s11izas6g985y9jklm3xprfsmym3v1g6xr84bavqvv"))))
+    (arguments
+     (substitute-keyword-arguments (package-arguments gmp)
+       ((#:configure-flags gmp-configure-flags)
+        `(cons* ,@(if (string-prefix? "powerpc64le-" (or (%current-target-system)
+                                                         (%current-system)))
+                      ;; The powerpc64 assembly code in this version of GMP
+                      ;; only supports the ELF ABI v1 but powerpc64le uses ELF
+                      ;; ABI v2, so use the generic C code instead.  This is
+                      ;; done by specifying the CPU type as “none”.
+                      ;;
+                      ;; According to the manual, “this will run quite slowly,
+                      ;; but it should be portable and should at least make it
+                      ;; possible to get something running if all else fails.”
+                      '("--host=none-unknown-linux-gnu")
+                      '())
+                ,gmp-configure-flags))))))
 
 (define mpfr-boot
   (package