set the EIGEN_MPL2_ONLY flag and add tests to make sure it is set for compile and codegen (#655)

CMakeLists.txt

@@ -46,6 +46,9 @@ else()
     message(WARNING "You are using an unsupported compiler. Compilation has only been tested with Clang (${CLANG_MIN_VERSION} and up), Apple Clang (${APPLE_CLANG_MIN_VERSION} and up), and GCC (${GCC_MIN_VERSION} and up).")
 endif()
 
+# Prevent Eigen from using any LGPL3 code
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DEIGEN_MPL2_ONLY")
+
 if($ENV{NGRAPH_USE_PREBUILT_LLVM})
     set(NGRAPH_USE_PREBUILT_LLVM TRUE)
 endif()

src/ngraph/codegen/compiler.cpp

@@ -148,6 +148,9 @@ void codegen::StaticCompiler::initialize()
     args.push_back("-mllvm");
     args.push_back("-inline-threshold=1000000");
 
+    // Prevent Eigen from using any LGPL3 code
+    args.push_back("-DEIGEN_MPL2_ONLY");
+
     // Prepare DiagnosticEngine
     IntrusiveRefCntPtr<DiagnosticOptions> diag_options = new DiagnosticOptions();
     diag_options->ErrorLimit = 20;

src/ngraph/node.cpp

@@ -26,6 +26,10 @@
 #include "ngraph/ops/result.hpp"
 #include "ngraph/placement.hpp"
 
+#if not defined(EIGEN_MPL2_ONLY)
+#error("The flag `EIGEN_MPL2_ONLY` must be defined");
+#endif
+
 using namespace std;
 using namespace ngraph;
 

test/codegen.cpp

@@ -26,6 +26,22 @@
 using namespace std;
 using namespace ngraph;
 
+TEST(codegen, eigen_gpl_test)
+{
+    // In order for this test to pass the in-memory compiler must define EIGEN_MPL2_ONLY
+    constexpr auto source = R"(
+#if not defined(EIGEN_MPL2_ONLY)
+#error("must define flag")
+#endif
+)";
+
+    codegen::Compiler compiler;
+    codegen::ExecutionEngine execution_engine;
+
+    auto module = compiler.compile(source);
+    ASSERT_NE(nullptr, module);
+}
+
 TEST(DISABLED_codegen, simple_return)
 {
     constexpr auto source = R"(extern "C" int test() { return 2+5; })";