diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -64,6 +64,9 @@
   endif()
   option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)
   option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
+  if(CMAKE_COMPILER_IS_GNUCXX)
+    set(USE_NO_MAYBE_UNINITIALIZED 1)
+  endif()
 
   include(CMakeParseArguments)
   include(AddLLVM)