Build with LTO if the compiler supports it

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.9 FATAL_ERROR)
 
 # TODO Remove this deprecated policy switch once we're on cmake 3.4 or later
 cmake_policy(SET CMP0065 OLD)
@@ -37,6 +37,21 @@ if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE INTERNAL "CMAKE_BUILD_TYPE")
 endif(NOT CMAKE_BUILD_TYPE)
 
+# Enable LTO if we're in a release build and LTO is supported
+include(CheckIPOSupported)
+check_ipo_supported(RESULT LTO_SUPPORTED OUTPUT error)
+if(LTO_SUPPORTED)
+    string(TOUPPER ${CMAKE_BUILD_TYPE} _CMAKE_BUILD_TYPE_UPPER)
+    if (_CMAKE_BUILD_TYPE_UPPER STREQUAL "DEBUG")
+        message(STATUS "LTO disabled because we're in a debug build")
+    else()
+        message(STATUS "LTO enabled")
+        set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+    endif()
+else()
+    message(WARNING "LTO disabled because compiler does not support it.")
+endif()
+
 if(USE_CLANG_TIDY)
     # note: for clang-tidy, we need cmake 3.6, or (if the return code should be handled correctly, e.g. on CI), we need 3.8.
     cmake_minimum_required(VERSION 3.8 FATAL_ERROR)

ChangeLog.txt

@@ -3,9 +3,8 @@ Version 0.11.0 (unreleased)
 Build changes:
 * Switch to Conan package manager
 * Allow an easy way to modify how the dependencies are found. This is mostly helpful for package maintainers.
-
-Other changes:
-* Now requires CMake 3.6 or later
+* Build with LTO if the compiler supports it
+* Now requires CMake 3.9 or later
 
 Improvements:
 * Display the file system configuration when mounting a file system

vendor/README

@@ -5,4 +5,5 @@ cryptopp: https://github.com/weidai11/cryptopp/tree/CRYPTOPP_8_2_0
  - changed: added CMakeLists.txt and cryptopp-config.cmake from https://github.com/noloader/cryptopp-cmake/tree/CRYPTOPP_8_2_0
  - changed: commented out line including winapifamily.h in CMakeLists.txt
  - changed: In CMakeLists.txt, rename BUILD_TESTING to CRYPTOPP_BUILD_TESTING so it doesn't clash with our BUILD_TESTING
- - changed: Fix Android compilation using patch file https://github.com/termux/termux-root-packages/files/4664745/config.h.patch.txt from https://github.com/cryfs/cryfs/issues/345
+ - changed: In CmakeLists.txt, add cmake_policy(SET CMP0069 NEW) to silence a warning
+ - changed: Fix Android compilation using patch file https://github.com/termux/termux-root-packages/files/4664745/config.h.patch.txt from https://github.com/cryfs/cryfs/issues/345

vendor/cryptopp/vendor_cryptopp/CMakeLists.txt

@@ -30,6 +30,7 @@ endif()
 message( STATUS "CMake version ${CMAKE_VERSION}" )
 
 cmake_minimum_required(VERSION 2.8.6)
+cmake_policy(SET CMP0069 NEW)
 if (${CMAKE_VERSION} VERSION_LESS "3.0.0")
   project(cryptopp)
   set(cryptopp_VERSION_MAJOR 8)