From febf9a0b070a7c5036f2b32f12167952f1597727 Mon Sep 17 00:00:00 2001
From: liaogang <liaogang@baidu.com>
Date: Fri, 20 Jan 2017 00:11:08 +0800
Subject: [PATCH] Add comments and CMAKE_SYSTEM_NAME

---
 cmake/system.cmake | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/cmake/system.cmake b/cmake/system.cmake
index 485cf0eea1c..3e472da7e0b 100644
--- a/cmake/system.cmake
+++ b/cmake/system.cmake
@@ -12,6 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Detects the OS and sets appropriate variables.
+# CMAKE_SYSTEM_NAME only give us a coarse-grained name,
+# but the name like centos is necessary in some scenes
+# to distinguish system for customization.
+#
+# for instance, protobuf libs path is <install_dir>/lib64
+# on CentOS, but <install_dir>/lib on other systems.
+
 IF(WIN32)
     SET(HOST_SYSTEM "win32")
 ELSE(WIN32)
@@ -45,7 +53,7 @@ ELSE(WIN32)
         ENDIF(EXISTS "/etc/redhat-release")
 
         IF(NOT HOST_SYSTEM)
-            SET(HOST_SYSTEM "unknown")
+            SET(HOST_SYSTEM ${CMAKE_SYSTEM_NAME})
         ENDIF()
 
     ENDIF(APPLE)
-- 
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