From 742fa9e316a10403ba7321596cc58eac63867f13 Mon Sep 17 00:00:00 2001
From: Igor Canadi <icanadi@fb.com>
Date: Mon, 20 Apr 2015 10:55:17 -0700
Subject: [PATCH] Fix compile with two gflags

Summary:
If the system has gflags with both `google` and `gflags` namespaces installed, we try to define GFLAGS as two things. This breaks the compile.

Fix: Use `else if` -- try compiling with `google` namespace only if compile with `gflags` failed

Test Plan: build_tools/build_detect_platform correctly identifies gflags

Reviewers: lgalanis

Reviewed By: lgalanis

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D37389
---
 build_tools/build_detect_platform | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

diff --git a/build_tools/build_detect_platform b/build_tools/build_detect_platform
index 8b12f3ba0..2ecf07aca 100755
--- a/build_tools/build_detect_platform
+++ b/build_tools/build_detect_platform
@@ -200,29 +200,19 @@ EOF
         JAVA_LDFLAGS="$JAVA_LDFLAGS -lsnappy"
     fi
 
-
     # Test whether gflags library is installed
     # http://code.google.com/p/gflags/
     # check if the namespace is gflags
-    $CXX $CFLAGS -x c++ - -o /dev/null 2>/dev/null  <<EOF
-      #include <gflags/gflags.h>
-      using namespace gflags;
-      int main() {}
-EOF
-    if [ "$?" = 0 ]; then
+    if echo "#include <gflags/gflags.h>\nusing namespace gflags;\nint main() {}" | \
+      $CXX $CFLAGS -x c++ - -o /dev/null 2>/dev/null; then
         COMMON_FLAGS="$COMMON_FLAGS -DGFLAGS=gflags"
         PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lgflags"
-    fi
-
-    # check if namespace is google
-    $CXX $CFLAGS -x c++ - -o /dev/null 2>/dev/null  <<EOF
-      #include <gflags/gflags.h>
-      using namespace google;
-      int main() {}
-EOF
-    if [ "$?" = 0 ]; then
-        COMMON_FLAGS="$COMMON_FLAGS -DGFLAGS=google"
-        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lgflags"
+    else
+      if echo "#include <gflags/gflags.h>\nusing namespace google;\nint main() {}" | \
+        $CXX $CFLAGS -x c++ - -o /dev/null ; then
+          COMMON_FLAGS="$COMMON_FLAGS -DGFLAGS=google"
+          PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lgflags"
+      fi
     fi
 
     # Test whether zlib library is installed