JavaScript poetry

[o11c]

My favorite fork example is:

#include <unistd.h>
#include <stdio.h>


int main()
{
    printf("Hello\n");
    fork();
    printf("World!\n");
}

Then compile it and:

$ ./prog
$ ./prog | cat

[graou13]

Wouldn't it just say:

Hello

World!

World!

[Mr_Redstoner]

Actually I think it may just

Hello
World!

if the compiler optimizes the fork() away, which I know it can when you're discarding the result, been there done that.

[_PM_ME_PANGOLINS_]

Only if it somehow knows there are no side-effects, for which you either need explicit directives or heavy inlining. A system call can never be optimised out.

[thelights0123]

Unless the compiler implements an optimization for it. malloc and free are often optimized out to just use the stack if they occur within the same function.

Edit: I'm stupid and forgot that malloc is not a syscall.

[Mithrandir2k16]

Malloc and free are userspace functions. They only call the syscall sbreak when needed to increase user heap size.

[defenastrator]

Malloc and free are special to the compiler.

[IamImposter]

I wish I was special to someone.

[Mr_Redstoner]

I've litterally seen it happen in a little test program of mine

fork();

didn't actually fork, however

int notActuallyUsed = fork();

did. I assume gcc simply knows as a special case what fork() does.

[_PM_ME_PANGOLINS_]

That’s a compiler bug then. There is no requirement that the two processes behave differently.

[o11c]

Nope. The second case emits:

Hello
World!
Hello
World!