I was being somewhat terse.

The (implied) claim is that the C standard has enough sources of undefined behavior that even a simple integer addition can't be relied upon to actually perform integer addition.

But the sources of undefined behavior for integer addition in C are well-known and very clear, and any instruction set that isn't an insane science project is going to have an instruction to add integers.

Thus my comment. Show me a C compiler that takes that code and miscompiles it. I don't care if it returns a constant, spits out an infinite loop, jumps to 0x0000, calls malloc, whatever. Show me a C compiler that takes those four lines of C code and emits something other than an integer addition instruction.