Add C++11 detection to cmake file.

Disable test and webmts targets when not C++11 and/or
std::unique_ptr are unavailable.

BUG=https://bugs.chromium.org/p/webm/issues/detail?id=1136

Change-Id: I717631bc6adea90c91e59862378328089e9aeec6

CMakeLists.txt

@@ -5,14 +5,52 @@
 ##  tree. An additional intellectual property rights grant can be found
 ##  in the file PATENTS.  All contributing project authors may
 ##  be found in the AUTHORS file in the root of the source tree.
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.2)
-project(LIBWEBM)
+project(LIBWEBM CXX)
 include("${CMAKE_CURRENT_SOURCE_DIR}/build/msvc_runtime.cmake")
 
+include(CheckCXXCompilerFlag)
+include(CheckCXXSourceCompiles)
+
 set(LIBWEBM_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
 
-# Enable C++11 support.
+# Build/test configuration flags. Defined here for visibility.
+option(ENABLE_WEBMTS "Enables WebM PES/TS support." ON)
+option(ENABLE_TESTS "Enables tests." OFF)
+set(GTEST_SRC_DIR "${LIBWEBM_SRC_DIR}/../googletest" CACHE PATH
+    "Path to Googletest git repository.")
+
+# This directory is where libwebm will build googletest dependencies.
+set(GTEST_BUILD_DIR "${CMAKE_BINARY_DIR}/googletest_build")
+
+if (ENABLE_TESTS OR ENABLE_WEBMTS)
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" OR
+      CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR
+      CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    CHECK_CXX_COMPILER_FLAG("-std=c++11" HAVE_CXX11)
+    if (HAVE_CXX11)
       set(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}" CACHE STRING "" FORCE)
+    endif ()
+  endif ()
+endif ()
+
+if (MSVC OR HAVE_CXX11)
+  # C++11 compile tests.
+  check_cxx_source_compiles("
+      #include <memory>
+      int main(int argc, const char* argv[]) {
+        std::unique_ptr<int> ptr;
+        (void)ptr;
+        return 0;
+      }"
+      HAVE_UNIQUE_PTR)
+endif ()
+
+if (NOT HAVE_UNIQUE_PTR)
+  set(ENABLE_TESTS OFF)
+  set(ENABLE_WEBMTS OFF)
+  message(WARNING "std::unique_ptr not supported, tests and webmts disabled.")
+endif ()
 
 # Turn up the warning levels.
 if (MSVC)
@@ -21,14 +59,6 @@ else ()
   set(CMAKE_CXX_FLAGS "-Wall -Wextra ${CMAKE_CXX_FLAGS}" CACHE STRING "" FORCE)
 endif ()
 
-# Test configuration flags. Defined here for visibility.
-option(ENABLE_TESTS "Enables tests." OFF)
-set(GTEST_SRC_DIR "${LIBWEBM_SRC_DIR}/../googletest" CACHE PATH
-    "Path to Googletest git repository.")
-
-# This directory is where libwebm will build googletest dependencies.
-set(GTEST_BUILD_DIR "${CMAKE_BINARY_DIR}/googletest_build")
-
 # Libwebm section.
 add_library(webm STATIC
             "${LIBWEBM_SRC_DIR}/hdr_util.cpp"
@@ -50,7 +80,7 @@ if(WIN32)
   # webm and webm.lib).
   set_target_properties(webm PROPERTIES PROJECT_LABEL libwebm)
   set_target_properties(webm PROPERTIES PREFIX lib)
-endif(WIN32)
+endif ()
 
 include_directories("${LIBWEBM_SRC_DIR}")
 
@@ -77,6 +107,7 @@ add_executable(vttdemux
                "${LIBWEBM_SRC_DIR}/webvttparser.h")
 target_link_libraries(vttdemux LINK_PUBLIC webm)
 
+if (ENABLE_WEBMTS)
   # webmts (PES/TS support) library section.
   add_library(webmts
               "${LIBWEBM_SRC_DIR}/common/libwebm_utils.cc"
@@ -94,6 +125,7 @@ target_link_libraries(webm2pes LINK_PUBLIC webm webmts)
   # webm2ts section.
   add_executable(webm2ts "${LIBWEBM_SRC_DIR}/vpxpes2ts_main.cc")
   target_link_libraries(webm2ts LINK_PUBLIC webm webmts)
+endif ()
 
 if (ENABLE_TESTS)
   add_subdirectory("${GTEST_SRC_DIR}" "${GTEST_BUILD_DIR}")
@@ -111,10 +143,12 @@ if (ENABLE_TESTS)
                  "${LIBWEBM_SRC_DIR}/testing/test_util.h")
   target_link_libraries(parser_tests LINK_PUBLIC gtest webm)
 
+  if (ENABLE_WEBMTS)
     add_executable(webm2pes_tests
                   "${LIBWEBM_SRC_DIR}/testing/test_util.cc"
                   "${LIBWEBM_SRC_DIR}/testing/test_util.h"
                   "${LIBWEBM_SRC_DIR}/testing/webm2pes_tests.cc")
     target_link_libraries(webm2pes_tests LINK_PUBLIC gtest webm webmts)
-endif (ENABLE_TESTS)
+  endif ()
+endif ()