From a087f7dc8abb1dc706e12cc51f8a89e63d7bbe03 Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <messmer@cryfs.org>
Date: Sun, 20 May 2018 14:15:18 -0700
Subject: [PATCH] Enforce OpenMP build by default, but allow disabling it with
 a cmake flag

---
 CMakeLists.txt                 |  1 +
 vendor/cryptopp/CMakeLists.txt | 17 +++++++++--------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index fce1ad0c..e6445124 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,6 +17,7 @@ require_clang_version(3.7)
 # Default value is not to build test cases
 option(BUILD_TESTING "build test cases" OFF)
 option(CRYFS_UPDATE_CHECKS "let cryfs check for updates and security vulnerabilities" ON)
+option(DISABLE_OPENMP "allow building without OpenMP libraries. This will cause performance degradations." OFF)
 
 # Default value is to build in release mode
 if(NOT CMAKE_BUILD_TYPE)
diff --git a/vendor/cryptopp/CMakeLists.txt b/vendor/cryptopp/CMakeLists.txt
index e4ba4835..07038838 100644
--- a/vendor/cryptopp/CMakeLists.txt
+++ b/vendor/cryptopp/CMakeLists.txt
@@ -4,14 +4,15 @@ add_library(cryptopp dummy.cpp)
 # note: include directory is called vendor_cryptopp instead of cryptopp to avoid include clashes with system headers
 target_include_directories(cryptopp SYSTEM INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
 
-find_package(OpenMP)
-if(OPENMP_FOUND)
-    message(STATUS "Building crypto++ with OpenMP")
-    set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS})
-    target_link_libraries(cryptopp PRIVATE ${OpenMP_CXX_FLAGS})
-else(OPENMP_FOUND)
-    message(WARNING "Did not find OpenMP. Performance might be degraded.")
-endif(OPENMP_FOUND)
+if(NOT DISABLE_OPENMP)
+    find_package(OpenMP)
+    if(OPENMP_FOUND)
+        set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS})
+        target_link_libraries(cryptopp PRIVATE ${OpenMP_CXX_FLAGS})
+    else(OPENMP_FOUND)
+        message(FATAL_ERROR "Did not find OpenMP. Build with -DDISABLE_OPENMP=ON if you want to allow this and are willing to take the performance hit.")
+    endif(OPENMP_FOUND)
+endif(NOT DISABLE_OPENMP)
 
 
 set(BUILD_TESTING OFF)