From 235437354e223550ef92845687560363efbbf82f Mon Sep 17 00:00:00 2001
From: Michael Uleysky <uleysky@poi.dvo.ru>
Date: Tue, 27 Oct 2015 15:54:54 +1000
Subject: [PATCH] Check and really use linker flags

---
 CMakeLists.txt                  | 34 ++++++++++++++++++++++++++++++++-
 cmake/modules/BuildModule.cmake |  2 +-
 src/CMakeLists.txt              |  2 +-
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 49fdd57..5116050 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,7 +25,9 @@ include_directories(include)
 
 # Checking compiler options
 set(default_options -Wall)
+set(linker_options -Wall)
 include(CheckCXXCompilerFlag)
+set(saved_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
 # C++11 is required
 CHECK_CXX_COMPILER_FLAG(-std=c++11 COMPILER_SUPPORTS_CXX11)
 CHECK_CXX_COMPILER_FLAG(-std=c++0x COMPILER_SUPPORTS_CXX0X)
@@ -37,28 +39,58 @@ else()
   message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
 endif()
 # Link time optimization check
+set(CMAKE_REQUIRED_FLAGS -flto)
 CHECK_CXX_COMPILER_FLAG(-flto COMPILER_SUPPORTS_FLTO)
 if(COMPILER_SUPPORTS_FLTO AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug")
  set(default_options ${default_options} -flto)
+ set(linker_options ${linker_options} -flto)
 endif()
+unset(CMAKE_REQUIRED_FLAGS)
+# Clang can use lto only with gold linker
+if(NOT COMPILER_SUPPORTS_FLTO)
+ set(CMAKE_REQUIRED_FLAGS -flto\ -fuse-ld=gold)
+ CHECK_CXX_COMPILER_FLAG(-flto\ -fuse-ld=gold COMPILER_SUPPORTS_FLTO_GOLD)
+ if(COMPILER_SUPPORTS_FLTO_GOLD AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug")
+  set(default_options ${default_options} -flto)
+  set(linker_options ${linker_options} -flto\ -fuse-ld=gold)
+ endif()
+ unset(CMAKE_REQUIRED_FLAGS)
+endif()
+# Dwarf-4 support check
+set(CMAKE_REQUIRED_FLAGS -gdwarf-4)
+CHECK_CXX_COMPILER_FLAG(-gdwarf-4 COMPILER_SUPPORTS_DWARF4)
+if(COMPILER_SUPPORTS_DWARF4 AND (CMAKE_BUILD_TYPE STREQUAL "Debug" OR CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo"))
+ set(default_options ${default_options} -gdwarf-4)
+ set(linker_options ${linker_options} -gdwarf-4)
+endif()
+unset(CMAKE_REQUIRED_FLAGS)
 # -ipo flag check (Intel compiler link time optimization)
+set(CMAKE_REQUIRED_FLAGS -ipo)
 CHECK_CXX_COMPILER_FLAG(-ipo COMPILER_SUPPORTS_IPO)
 if(COMPILER_SUPPORTS_IPO AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug")
  set(default_options ${default_options} -ipo)
+ set(linker_options ${linker_options} -ipo)
 endif()
+unset(CMAKE_REQUIRED_FLAGS)
 # Default hidden visibility check
+set(CMAKE_REQUIRED_FLAGS -fvisibility=hidden)
 CHECK_CXX_COMPILER_FLAG(-fvisibility=hidden COMPILER_SUPPORTS_HIDDEN)
 if(COMPILER_SUPPORTS_HIDDEN)
  set(default_options ${default_options} -fvisibility=hidden)
+ set(linker_options ${linker_options} -fvisibility=hidden)
 endif()
+unset(CMAKE_REQUIRED_FLAGS)
 # Export dynamic. Required as modules mast call functions from main programm
+set(CMAKE_REQUIRED_FLAGS -Wl,--export-dynamic)
 CHECK_CXX_COMPILER_FLAG(-Wl,--export-dynamic COMPILER_SUPPORTS_EXPORTDYNAMIC)
 if(COMPILER_SUPPORTS_EXPORTDYNAMIC)
- set(default_options ${default_options} -Wl,--export-dynamic)
+ set(linker_options ${linker_options} -Wl,--export-dynamic)
 else()
  message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no support of --export-dynamic. Please use a different C++ compiler.")
 endif()
+unset(CMAKE_REQUIRED_FLAGS)
 add_compile_options(${default_options})
+set(CMAKE_REQUIRED_FLAGS ${saved_CMAKE_REQUIRED_FLAGS})
 
 file(GLOB modules modules/*)
 file(GLOB extramodules extramodules/*)
diff --git a/cmake/modules/BuildModule.cmake b/cmake/modules/BuildModule.cmake
index bf19be3..9452cca 100644
--- a/cmake/modules/BuildModule.cmake
+++ b/cmake/modules/BuildModule.cmake
@@ -6,6 +6,6 @@ if(MODULE_${modname}_STATIC)
 else()
  include_directories(${MODULE_ADDITIONAL_INCLUDES}) 
  add_library(${modname} MODULE ${srcs} ${MODULE_ADDITIONAL_SOURCES})
- target_link_libraries(${modname} ${MODULE_ADDITIONAL_LIBRARIES})
+ target_link_libraries(${modname} ${linker_options} ${MODULE_ADDITIONAL_LIBRARIES})
 endif()
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9c44e10..7a5218b 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -39,5 +39,5 @@ add_executable(${EXENAME} ${srcs} ${FLEX_LScanner_OUTPUTS} ${BISON_GParser_OUTPU
 set_source_files_properties(init.cpp PROPERTIES OBJECT_DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/grammatical.h)
 add_custom_command(OUTPUT grammatical.h COMMAND cp grammatical.hpp grammatical.h DEPENDS grammatical.hpp WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 
-target_link_libraries(${EXENAME} ${dl} ${pthread} ${MODULES_LIBS})
+target_link_libraries(${EXENAME} ${linker_options} ${dl} ${pthread} ${MODULES_LIBS})
 set_target_properties(${EXENAME} PROPERTIES POSITION_INDEPENDENT_CODE ON)