From: Azat Khuzhin <a3at.mail@gmail.com>
Date: Sun, 4 Nov 2018 16:48:11 +0000 (+0300)
Subject: cmake: do not detect _GNU_SOURCE/__GNU_LIBRARY__ if it is cached
X-Git-Tag: release-2.1.9-beta^2~59
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b52c6498753262549bcf088e7c7836ddd4d50ce1;p=libevent

cmake: do not detect _GNU_SOURCE/__GNU_LIBRARY__ if it is cached

(cherry picked from commit 3ed93997387296e374d8a2dd770e43ddfa3328e9)
---

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 48885a32..ae0be78d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -256,7 +256,7 @@ if (SOLARIS)
 endif()
 
 # Check if _GNU_SOURCE is available.
-if (NOT _GNU_SOURCE)
+if (NOT DEFINED _GNU_SOURCE)
   CHECK_SYMBOL_EXISTS(__GNU_LIBRARY__ "features.h" _GNU_SOURCE)
 
   if (NOT _GNU_SOURCE)