From 5cb0151510c8b85476d2de1d3c036927a0341a22 Mon Sep 17 00:00:00 2001
From: Kevin Ryde <user42@zip.com.au>
Date: Tue, 10 Aug 2004 00:19:47 +0000
Subject: [PATCH] (scm_putenv): Use unsetenv to remove entries (ie. no "="),
 when available, for the benefit of FreeBSD and other systems where putenv()
 doesn't do that itself.

---
 libguile/posix.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libguile/posix.c b/libguile/posix.c
index 9589526fc..6fccb1788 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -1238,6 +1238,18 @@ SCM_DEFINE (scm_putenv, "putenv", 1, 0, 0,
   char *ptr;
 
   SCM_VALIDATE_STRING (1, str);
+
+  /* No '=' in the argument means we should remove the variable from the
+     environment.  Not all putenv()s understand this (for instance FreeBSD
+     4.8 doesn't).  To be safe, we do it explicitely using unsetenv. */
+#ifdef HAVE_UNSETENV
+  if (strchr (SCM_STRING_CHARS (str), '=') == NULL)
+    {
+      unsetenv (SCM_STRING_CHARS (str));
+      return SCM_UNSPECIFIED;
+    }
+#endif
+
   /* must make a new copy to be left in the environment, safe from gc.  */
   ptr = malloc (SCM_STRING_LENGTH (str) + 1);
   if (ptr == NULL)