From f770b9e6c54a0e149a45c458fd6c17eead00cf98 Mon Sep 17 00:00:00 2001
From: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Date: Wed, 30 Dec 2015 00:37:51 +0200
Subject: [PATCH] libstore: mmap() returns MAP_FAILED, not NULL on failure

---
 src/libstore/build.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 4192c6c65..02faa5c9d 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2175,7 +2175,7 @@ void DerivationGoal::startBuilder()
             size_t stackSize = 1 * 1024 * 1024;
             char * stack = (char *) mmap(0, stackSize,
                 PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
-            if (!stack) throw SysError("allocating stack");
+            if (stack == MAP_FAILED) throw SysError("allocating stack");
             int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD;
             if (!fixedOutput) flags |= CLONE_NEWNET;
             pid_t child = clone(childEntry, stack + stackSize, flags, this);