From ca2df2e22153e422d67586898e098d167964dc16 Mon Sep 17 00:00:00 2001
From: Jari Vetoniemi <mailroxas@gmail.com>
Date: Tue, 25 Aug 2015 02:14:57 +0300
Subject: [PATCH] CMake: Handle compiler flags better

---
 CMake/GCCCompatibleCompilerOptions.cmake | 53 ++++++++++++++++++++++++
 CMakeLists.txt                           | 21 ++++------
 README.md                                |  2 +-
 3 files changed, 63 insertions(+), 13 deletions(-)
 create mode 100644 CMake/GCCCompatibleCompilerOptions.cmake

diff --git a/CMake/GCCCompatibleCompilerOptions.cmake b/CMake/GCCCompatibleCompilerOptions.cmake
new file mode 100644
index 0000000..830bee0
--- /dev/null
+++ b/CMake/GCCCompatibleCompilerOptions.cmake
@@ -0,0 +1,53 @@
+include(CheckCCompilerFlag)
+
+# Add list of compiler warnings
+# Every warning gets checked with check_c_compiler_flags
+function(add_compiler_warnings)
+   foreach (flag ${ARGN})
+      check_c_compiler_flag(${flag} ok)
+      if (ok)
+         add_compile_options(${flag})
+      endif ()
+   endforeach ()
+endfunction ()
+
+# Create new ${EXE,MODULE,SHARED}_LINKER_FLAGS build type for list of linker flags
+# Every linker flag gets checked with check_c_compiler_flag
+function(create_custom_linker_flags name)
+   foreach (flag ${ARGN})
+      check_c_compiler_flag(-Wl,${flag} ok)
+      if (ok)
+         if (ldflags)
+            set(ldflags "${ldflags},${flag}")
+         else ()
+            set(ldflags "-Wl,${flag}")
+         endif ()
+      endif ()
+   endforeach ()
+
+   string(TOUPPER ${name} upper)
+   set(CMAKE_EXE_LINKER_FLAGS_${upper} "${ldflags}" CACHE STRING "${name} exe linker flags" FORCE)
+   set(CMAKE_MODULE_LINKER_FLAGS_${upper} "${ldflags}" CACHE STRING "${name} module linker flags" FORCE)
+   set(CMAKE_SHARED_LINKER_FLAGS_${upper} "${ldflags}" CACHE STRING "${name} shared linker flags" FORCE)
+   mark_as_advanced(CMAKE_EXE_LINKER_FLAGS_${upper} CMAKE_SHARED_LINKER_FLAGS_${upper} CMAKE_MODULE_LINKER_FLAGS_${upper})
+endfunction ()
+
+# Create new {C,CXX}_FLAGS build type for list of compiler flags
+# Every compiler flag gets checked with check_c_compiler_flag
+function(create_custom_compiler_flags name)
+   foreach (flag ${ARGN})
+      check_c_compiler_flag(${flag} ok)
+      if (ok)
+         if (cflags)
+            set(cflags "${cflags} ${flag}")
+         else ()
+            set(cflags "${flag}")
+         endif ()
+      endif ()
+   endforeach ()
+
+   string(TOUPPER ${name} upper)
+   set(CMAKE_C_FLAGS_${upper} "${cflags}" CACHE STRING "${name} C flags" FORCE)
+   set(CMAKE_CXX_FLAGS_${upper} "${cflags}" CACHE STRING "${name} CXX flags" FORCE)
+   mark_as_advanced(CMAKE_CXX_FLAGS_${upper} CMAKE_C_FLAGS_${upper})
+endfunction ()
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86e23f2..fd84a75 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,20 +33,17 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin")
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib")
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib")
 
+# Compiler options
 if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
-   set(ldflags -Wl,-O1,--no-undefined,--sort-common,--as-needed,-z,relro,-z,now)
-   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${ldflags}")
-   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${ldflags}")
-   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${ldflags}")
-
-   if ("${CMAKE_C_FLAGS}" STREQUAL "")
-      add_definitions(-O2)
-      add_definitions(-fstack-protector-strong -fstack-check -flto)
+   include(GCCCompatibleCompilerOptions)
+   add_compiler_warnings(-Wall -Wextra -Wno-variadic-macros -Wno-long-long -Wformat=2 -Winit-self -Wfloat-equal -Wcast-align -Wpointer-arith -Wmissing-prototypes -Wsuggest-attribute=pure -Wsuggest-attribute=const)
+   create_custom_linker_flags(Upstream -O1 --sort-common --as-needed -z,relro -z,now)
+   check_c_compiler_flag(-fstack-protector-strong ok)
+   if (ok)
+      create_custom_compiler_flags(Upstream -g -O2 -fstack-protector-strong --param ssp-buffer-size=4 -fstack-check -flto)
+   else ()
+      create_custom_compiler_flags(Upstream -g -O2 -fstack-protector-all --param ssp-buffer-size=4 -fstack-check -flto)
    endif ()
-
-   add_definitions(
-      -Wall -Wextra -Wno-variadic-macros -Wno-long-long -Wformat=2 -Winit-self -Wfloat-equal
-      -Wcast-align -Wpointer-arith -Wmissing-prototypes -Wsuggest-attribute=pure -Wsuggest-attribute=const)
 endif ()
 
 # -std=c99 -fpic -fpie -D_DEFAULT_SOURCE
diff --git a/README.md b/README.md
index 8b36a6c..1dc56ef 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 ## Building
 
     mkdir target && cd target                # - create build target directory
-    cmake -DCMAKE_INSTALL_PREFIX=build ..    # - run CMake, set install directory
+    cmake -DCMAKE_BUILD_TYPE=Upstream ..     # - run CMake
     make                                     # - compile
 
 ## License