I think the keyword might be an 8k executable, not 8k of code. If I compile the example with clang on my box (linux x86_64) I get a 17K executable, for which the .text section (containing pretty much the runnable code)is 0x291 (661) bytes with the debug build and 0x255 (597) bytes with -O3.

If I dig into the .text segment of the optimized executable, only 235 bytes belong to the main function (others are stuff like __libc_csu_init and register_tm_clones). Looking at the assembly the loop would be about 123 bytes.

So lots of overhead, but I wouldn't say it is in the nested loop.