Visual Studio - optimization - remove unused function - visual-studio

Question

I use /opt:ref /VERBOSE option on a Visual Studio 2012 besides having activated "Whole Program Optimization - > Use Link Time Code Generation". /opt:ref is supposed to remove unused functions although I had the impression that specifying "Use Link Time Code Generation" was supposed to remove unused functions by default.
In my test program I use a test function that I expect to be removed from the final executable and VS output seems to confirm that:
Discarded "int __cdecl testMe(int)" (?testMe##YAHH#Z) from Test.obj
But looking over the *.asm file generated with /FAs I can see the function listed:
; Function compile flags: /Ogtp
; File c:\users\g.m\documents\visual studio 2012\projects\Test.cpp
; COMDAT ?testMe##YAHH#Z
_TEXT SEGMENT
?testMe##YAHH#Z PROC ; testMe, COMDAT
...
So, is it removed or not from the final image ?
EDIT:
trivial code to be optimized out
static int testMe(int i)
{
return i + 1;
}
int main()
{
auto res = testMe(0);
}
What I find quite suspicious is even in the case function is "static" it still appears in the *.asm file

Answer 1

What seems to be happening here is that the compiler has not fully optimised out the function at the time it generates the assembly (though you haven't posted the full listing, nor the original function, so it's hard to be sure), but the linker is able to see that it is unreferenced, and has discarded it.
Linking happens after assembly generation, so anything the linker does is not indicated by the intermediate assembly output.
You would know for sure only by looking at the final executable, but I suspect the linker is telling the truth, and has removed your function.
Update:
Testing your code locally confirms my suspicion. The compiler does not optimise out the dead code, but the linker does.