From 7c60615e29a1aab7922139183d191cc8cedd5c7f Mon Sep 17 00:00:00 2001
From: Diego Nicola Barbato <dnbarbato@posteo.de>
Date: Mon, 8 Jun 2020 02:31:17 +0200
Subject: [PATCH] gnu: python-matplotlib: Fix rounding errors on x86 CPUs.

Fixes <https://debbugs.gnu.org/40406>.
Reported by Diego Nicola Barbato <dnbarbato@posteo.de>.

* gnu/packages/python-xyz.scm (python-matplotlib)[arguments]: Set the
environment variable CFLAGS to -ffloat-store.
---
 gnu/packages/python-xyz.scm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gnu/packages/python-xyz.scm b/gnu/packages/python-xyz.scm
index 94e63d1c74..f0b96c6fb0 100644
--- a/gnu/packages/python-xyz.scm
+++ b/gnu/packages/python-xyz.scm
@@ -81,6 +81,7 @@
 ;;; Copyright © 2020 Josh Holland <josh@inv.alid.pw>
 ;;; Copyright © 2020 Yuval Kogman <nothingmuch@woobling.org>
 ;;; Copyright © 2020 Michael Rohleder <mike@rohleder.de>
+;;; Copyright © 2020 Diego N. Barbato <dnbarbato@posteo.de>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -4744,6 +4745,10 @@ convert between colorspaces like sRGB, XYZ, CIEL*a*b*, CIECAM02, CAM02-UCS, etc.
                ;; has not effect.
                (setenv "LD_LIBRARY_PATH" (string-append cairo "/lib"))
                (setenv "HOME" (getcwd))
+               ;; Fix rounding errors when using the x87 FPU.
+               ,@(if (string-prefix? "i686" (%current-system))
+                     '((setenv "CFLAGS" "-ffloat-store"))
+                     '())
                (call-with-output-file "setup.cfg"
                  (lambda (port)
                    (format port "[directories]~%
-- 
2.26.2