From: Alexander Dahl <alex@netz39.de>
Date: Wed, 28 Oct 2015 16:04:13 +0100
Subject: [PATCH] cmake: use INTERPROCEDURAL_OPTIMIZATION target property

Instead of hacking on compiler flags use the cmake way for handling
interprocedural optimization. Tests showed cmake currently ignores this
for gcc and clang, at least on Debian Wheezy and Jessie. This actually
results in no interprocedural optimization for the moment. However it
allows to compile fastd against a toolchain without LTO support, which
was broken because of a hack included here for finding binutils.

According to the upstream author of fastd the main reason for enabling
LTO was binary size on an OpenWRT target for Freifunk Gluon, where they
have very few space left on devices with only 4 MB flash memory.

Signed-off-by: Alexander Dahl <post@lespocky.de>
---
 cmake/CMakeFindBinUtils.cmake |  7 -------
 cmake/checks.cmake            | 14 --------------
 src/CMakeLists.txt            |  9 +++++++++
 3 files changed, 9 insertions(+), 21 deletions(-)
 delete mode 100644 cmake/CMakeFindBinUtils.cmake

diff --git a/cmake/CMakeFindBinUtils.cmake b/cmake/CMakeFindBinUtils.cmake
deleted file mode 100644
index 753577a..0000000
--- a/cmake/CMakeFindBinUtils.cmake
+++ /dev/null
@@ -1,7 +0,0 @@
-if(CMAKE_COMPILER_IS_GNUCC)
-  find_program(CMAKE_AR NAMES ${_CMAKE_TOOLCHAIN_PREFIX}gcc-ar HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
-  find_program(CMAKE_NM NAMES ${_CMAKE_TOOLCHAIN_PREFIX}gcc-nm HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
-  find_program(CMAKE_RANLIB NAMES ${_CMAKE_TOOLCHAIN_PREFIX}gcc-ranlib HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
-endif(CMAKE_COMPILER_IS_GNUCC)
-
-include(${CMAKE_ROOT}/Modules/CMakeFindBinUtils.cmake)
diff --git a/cmake/checks.cmake b/cmake/checks.cmake
index f9f0399..3c1f38b 100644
--- a/cmake/checks.cmake
+++ b/cmake/checks.cmake
@@ -10,20 +10,6 @@ if(ARCH_X86 OR ARCH_X86_64)
 endif(ARCH_X86 OR ARCH_X86_64)
 
 
-
-if(ENABLE_LTO)
-  set(CFLAGS_LTO "-flto")
-  set(CFLAGS_NO_LTO "-fno-lto")
-
-  check_c_compiler_flag("-fwhole-program" HAVE_FLAG_WHOLE_PROGRAM)
-  if(HAVE_FLAG_WHOLE_PROGRAM)
-    set(LDFLAGS_LTO "-flto -fwhole-program")
-  else(HAVE_FLAG_WHOLE_PROGRAM)
-    set(LDFLAGS_LTO "-flto")
-  endif(HAVE_FLAG_WHOLE_PROGRAM)
-endif(ENABLE_LTO)
-
-
 check_c_source_compiles("
 #include <sys/types.h>
 #include <sys/socket.h>
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e7dd5d1..4991656 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -47,6 +47,15 @@ add_executable(fastd
 set_property(TARGET fastd PROPERTY COMPILE_FLAGS "${FASTD_CFLAGS}")
 set_property(TARGET fastd PROPERTY LINK_FLAGS "${PTHREAD_LDFLAGS} ${UECC_LDFLAGS_OTHER} ${NACL_LDFLAGS_OTHER} ${OPENSSL_CRYPTO_LDFLAGS_OTHER} ${JSONC_LDFLAGS_OTHER} ${LDFLAGS_LTO}")
 set_property(TARGET fastd APPEND PROPERTY INCLUDE_DIRECTORIES ${CAP_INCLUDE_DIR} ${NACL_INCLUDE_DIRS} ${JSONC_INCLUDE_DIRS})
+if(ENABLE_LTO)
+	set_target_properties(fastd PROPERTIES
+		INTERPROCEDURAL_OPTIMIZATION ON
+	)
+else(ENABLE_LTO)
+	set_target_properties(fastd PROPERTIES
+		INTERPROCEDURAL_OPTIMIZATION OFF
+	)
+endif(ENABLE_LTO)
 target_link_libraries(fastd protocols methods ciphers macs ${RT_LIBRARY} ${CAP_LIBRARY} ${UECC_LIBRARIES} ${NACL_LIBRARIES} ${OPENSSL_CRYPTO_LIBRARIES} ${JSONC_LIBRARIES})
 
 add_dependencies(fastd version)
-- 
2.1.4