232
unsafeCode (lemmy.ml)
submitted 2 months ago by cm0002@lemmy.world to c/programmer_humor@programming.dev
14 comments fedilink hide all child comments
you are viewing a single comment's thread
view the rest of the comments
[-] Kwdg@discuss.tchncs.de 26 points 2 months ago

Not needed, main in C++ implicitly returns 0 if there is no return

[-] 30p87@feddit.org 0 points 2 months ago

Should ≠ Needs to

You can do it, and it will work, but it's unclean and not best-practice. I wouldn't be surprised if it's undefined behaviour.

[-] xmunk@sh.itjust.works 23 points 2 months ago

Just to clarify. It is defined behavior - there's plenty of undefined behavior in C but that ain't one of them.

[-] FuckBigTech347@lemmygrad.ml 3 points 2 months ago

Interesting feature, I had no idea. I just verified this with gcc and indeed the return register is always set to 0 before returning unless otherwise specified.

spoiler

int main(void)
{
    int foo = 10;
}

produces:

push   %rbp
mov    %rsp,%rbp
movl   $0xa,-0x4(%rbp) # Move 10 to stack variable
mov    $0x0,%eax       # Return 0
pop    %rbp
ret

int main(void)
{
    int foo = 10;
    return foo;
}

produces:

push   %rbp
mov    %rsp,%rbp
movl   $0xa,-0x4(%rbp) # Move 10 to stack variable
mov    -0x4(%rbp),%eax # Return foo
pop    %rbp
ret

this post was submitted on 11 Feb 2025
232 points (94.6% liked)

Programmer Humor

22921 readers
82 users here now

Welcome to Programmer Humor!

This is a place where you can post jokes, memes, humor, etc. related to programming!

For sharing awful code theres also Programming Horror.

Rules

founded 2 years ago
MODERATORS
Feyter@programming.dev
anzo@programming.dev
BurningTurtle@programming.dev
pylapp@programming.dev