1.0.11.1: Handle set-but-empty environment variables

[sbcl.git] / contrib / asdf-install / installer.lisp

diff --git a/contrib/asdf-install/installer.lisp b/contrib/asdf-install/installer.lisp
index 0af1455..b43f15a 100644 (file)
--- a/contrib/asdf-install/installer.lisp
+++ b/contrib/asdf-install/installer.lisp
@@ -2,8 +2,9 @@
 
 (defvar *proxy* (posix-getenv "http_proxy"))
 (defvar *cclan-mirror*
-  (or (posix-getenv "CCLAN_MIRROR")
-      "http://ftp.linux.org.uk/pub/lisp/cclan/"))
+  (let ((mirror (posix-getenv "CCLAN_MIRROR")))
+    (or (and (not (string= mirror "")) mirror)
+        "http://ftp.linux.org.uk/pub/lisp/cclan/")))
 
 (defun directorify (name)
   ;; input name may or may not have a training #\/, but we know we