llvm/test/TableGen/nested_ifdef.inc - third_party/llvm-project - Git at Google

 #ifndef NESTED_IFDEF
 #define NESTED_IFDEF

 def foo;

 #ifndef HAHA
 def haha;
 #endif

 #endif
	#ifndef NESTED_IFDEF
	#define NESTED_IFDEF

	def foo;

	#ifndef HAHA
	def haha;
	#endif

	#endif