Hacker News Reader

Comment by echoangle | Hacker News Reader

I'm also confused that an uncalled function is even compiled and linked, wouldn't it make sense to remove it entirely if the compiler can detect that it's never called?

View on HN

If it's declared as static, maybe (well, usually, in my experience. You'll also usually get an unused warning). Otherwise the compiler can't assume some other compilation unit won't want it. Linkers can perform a garbage collection pass but they don't often do it by default and they often need finer grained information from the compiler (see the gcc arguments --ffunction-sections and -Wl,--gc-sections)

I can understand adding the 'unreachable' function to the object file, I can even understand plugging it into the final executable, what I (and most other people) object to is making it the de-facto entry point.

This is literally the opposite behaviour compared to what is written in the source code, even when you "assume the infinite loop terminates".

That's the problem with UB, once you hit it (or even have it in your code), you can't really trust anything about the execution anymore. That the function is called isn't something the compiler does on purpose, it's just that the main function is compiled empty due to the UB and the function directly behind it is executed because the CPU just keeps looking for the next instruction.

Yeah, that's what UB does. You get to see the arbitrary behaviour of the underlying machine with whatever the compiler produces.

Reply on news.ycombinator.com