From 6d2b43915f8a628588f03136b3008902f7643e06 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Fri, 15 Apr 2016 19:47:35 +0200
Subject: [PATCH] syscalls: 'terminal-columns' ignores non-file ports.

* guix/build/syscalls.scm (terminal-columns): Call
'terminal-window-size' only when PORT is a file port.
* tests/syscalls.scm ("terminal-columns non-file port"): New test.
---
 guix/build/syscalls.scm | 10 ++++++----
 tests/syscalls.scm      |  4 ++++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index ed833c10b2..5ce0abbb48 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -915,10 +915,12 @@ always a positive integer."
 
   (catch 'system-error
     (lambda ()
-      (match (window-size-columns (terminal-window-size port))
-        ;; Things like Emacs shell-mode return 0, which is unreasonable.
-        (0 (fall-back))
-        ((? number? columns) columns)))
+      (if (file-port? port)
+          (match (window-size-columns (terminal-window-size port))
+            ;; Things like Emacs shell-mode return 0, which is unreasonable.
+            (0 (fall-back))
+            ((? number? columns) columns))
+          (fall-back)))
     (lambda args
       (let ((errno (system-error-errno args)))
         (if (= errno ENOTTY)
diff --git a/tests/syscalls.scm b/tests/syscalls.scm
index 1b443be0c8..24ea8f5e60 100644
--- a/tests/syscalls.scm
+++ b/tests/syscalls.scm
@@ -257,4 +257,8 @@
 (test-assert "terminal-columns"
   (> (terminal-columns) 0))
 
+(test-assert "terminal-columns non-file port"
+  (> (terminal-columns (open-input-string "Join us now, share the software!"))
+     0))
+
 (test-end)