ruby

compiler that has no defined behaviour. everything is UB. is this anything

Given the following C++ (not C!) input file:

#include <stdio.h>

int main() {
    while (1);
}

void oopsies() {
    printf("tee hee fucky wucky :3");
}

Compiling this with clang 13 or newer, with -O1 or higher, results in the output:

> ./compiled
tee hee fucky wucky :3

Godbolt reveals the following output:

main:                                   # @main
oopsies():                            # @oopsies()
        push    rax
        mov     edi, offset .L.str
        xor     eax, eax
        call    printf
        pop     rax
        ret
.L.str:
        .asciz  "tee hee fucky wucky :3"

which is uhhhhh Yeah Thats Not Right

what i think is happening:

• clang sees infinite loop and goes "ah cool, i don't need to insert a ret here since this wont terminate
• clang also decides to optimize out the infinite loop for Some Fucking Reason
• as a result, we're left with a completely empty main with no ret

is there like some undefined behaviour Spooky Activity going on here? why is it Do That? and why only for c++ and not c, where it correctly keeps the infinite loop?