moved/cleaned up gcc-ar/gcc-ranlib checking #245

CMakeLists.txt

@@ -7,6 +7,31 @@ project(TokuDB)
 set(CMAKE_SHARED_LIBRARY_LINK_C_FLAGS "")
 set(CMAKE_SHARED_LIBRARY_LINK_CXX_FLAGS "")
 
+## Versions of gcc >= 4.9.0 require special version of 'ar' and 'ranlib' for
+## link-time optimizations to work properly.
+##
+## From https://gcc.gnu.org/gcc-4.9/changes.html:
+##
+##     When using a linker plugin, compiling with the -flto option now
+##     generates slim objects files (.o) which only contain intermediate
+##     language representation for LTO. Use -ffat-lto-objects to create
+##     files which contain additionally the object code. To generate
+##     static libraries suitable for LTO processing, use gcc-ar and
+##     gcc-ranlib; to list symbols from a slim object file use
+##     gcc-nm. (Requires that ar, ranlib and nm have been compiled with
+##     plugin support.)
+if ((CMAKE_CXX_COMPILER_ID STREQUAL GNU) AND
+    NOT (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.9.0"))
+  find_program(gcc_ar "gcc-ar")
+  if (gcc_ar)
+    set(CMAKE_AR "${gcc_ar}")
+  endif ()
+  find_program(gcc_ranlib "gcc-ranlib")
+  if (gcc_ranlib)
+    set(CMAKE_RANLIB "${gcc_ranlib}")
+  endif ()
+endif()
+
 include(TokuFeatureDetection)
 include(TokuSetupCompiler)
 include(TokuSetupCTest)

cmake_modules/TokuSetupCompiler.cmake

@@ -137,14 +137,6 @@ if (CMAKE_CXX_COMPILER_ID STREQUAL Clang)
   set(CMAKE_C_FLAGS_RELEASE "-g -O3 ${CMAKE_C_FLAGS_RELEASE} -UNDEBUG")
   set(CMAKE_CXX_FLAGS_RELEASE "-g -O3 ${CMAKE_CXX_FLAGS_RELEASE} -UNDEBUG")
 else ()
-  if (CMAKE_CXX_COMPILER_ID MATCHES GNU)
-    ## Versions of gcc >= 4.9.0 require special version of 'ar' and 'ranlib' for
-    ## link-time optimizations to work properly.
-    if (NOT (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.9.0"))
-      set(CMAKE_AR "gcc-ar")
-      set(CMAKE_RANLIB "gcc-ranlib")
-    endif()
-  endif()
   # we overwrite this because the default passes -DNDEBUG and we don't want that
   set(CMAKE_C_FLAGS_RELWITHDEBINFO "-flto -fuse-linker-plugin ${CMAKE_C_FLAGS_RELWITHDEBINFO} -g -O3 -UNDEBUG")
   set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-flto -fuse-linker-plugin ${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -g -O3 -UNDEBUG")