Null references redux

[bearophile]

Rainer Deyke:

> Of course, a good optimizer can still reorder the declarations in this
> case, or even eliminate the whole function body (since it doesn't do
> anything).

LLVM has a good optimizer. If you try the LLVM demo on C code with LTO activated:
http://llvm.org/demo/index.cgi

This C code:

   void bar(int foo) {
     int a;
     int c = 3;
     if (foo) {
       a = 1;
     } else {
       a = 2;
     }
   }

Produces an useful warining:
/tmp/webcompile/_16254_0.c:3: warning: unused variable 'c'

And an empty function:

define void @bar(i32 %foo) nounwind readnone {
entry:
	ret void
}

Bye,
bearophile