From 3c5861c340cb45cf626f61e022d0aa2805f16569 Mon Sep 17 00:00:00 2001
From: Ian Lynagh <igloo@earth.li>
Date: Thu, 3 Jul 2008 19:06:03 +0000
Subject: Allow C's unsetenv to return either void or int Fixes, and patch from
 donn in, trac #2352.

---
 System/Posix/Env.hsc |  7 ++++---
 configure.ac         | 13 +++++++++++++
 include/HsUnix.h     | 10 ++++++++++
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/System/Posix/Env.hsc b/System/Posix/Env.hsc
index df7a3fe..39db08c 100644
--- a/System/Posix/Env.hsc
+++ b/System/Posix/Env.hsc
@@ -79,10 +79,11 @@ getEnvironment = do
 unsetEnv :: String -> IO ()
 #ifdef HAVE_UNSETENV
 
-unsetEnv name = withCString name c_unsetenv
+unsetEnv name = withCString name $ \ s ->
+  throwErrnoIfMinus1_ "unsetenv" (c_unsetenv s)
 
-foreign import ccall unsafe "unsetenv"
-   c_unsetenv :: CString -> IO ()
+foreign import ccall unsafe "__hsunix_unsetenv"
+   c_unsetenv :: CString -> IO CInt
 #else
 unsetEnv name = putEnv (name ++ "=")
 #endif
diff --git a/configure.ac b/configure.ac
index 97a3f2f..5283a55 100644
--- a/configure.ac
+++ b/configure.ac
@@ -75,6 +75,19 @@ case "$cv_func_usleep_return_type" in
   ;;
 esac
 
+###  POSIX.1003.1 unsetenv returns 0 or -1 (EINVAL), but older implementations
+###  in common use return void.
+AC_CACHE_CHECK([return type of unsetenv], cv_func_unsetenv_return_type,
+  [AC_EGREP_HEADER(changequote(<, >)<void[      ]+unsetenv>changequote([, ]),
+                   /usr/include/stdlib.h,
+                   [cv_func_unsetenv_return_type=void],
+                   [cv_func_unsetenv_return_type=int])])
+case "$cv_func_unsetenv_return_type" in
+  "void" )
+    AC_DEFINE([UNSETENV_RETURNS_VOID], [1], [Define if stdlib.h declares unsetenv to return void.])
+  ;;
+esac
+
 dnl ** sometimes RTLD_NEXT is hidden in #ifdefs we really don't wan to set
 AC_MSG_CHECKING(for RTLD_NEXT from dlfcn.h)
 AC_EGREP_CPP(yes,
diff --git a/include/HsUnix.h b/include/HsUnix.h
index 7aee685..4afd51a 100644
--- a/include/HsUnix.h
+++ b/include/HsUnix.h
@@ -190,4 +190,14 @@ INLINE int __hscore_setrlimit(int resource, struct rlimit *rlim) {
 }
 #endif
 
+INLINE int __hsunix_unsetenv(const char *name)
+{
+#ifdef UNSETENV_RETURNS_VOID
+    unsetenv(name);
+    return 0;
+#else
+    return unsetenv(name);
+#endif
+}
+
 #endif
-- 
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