A awesome^H^H^H^H^H^H^Hdisgusting use of the stack in C.

sls.c

#include <stdio.h>
#include <setjmp.h>
#include <stddef.h>
#include <string.h>

#define NORETURN __attribute__((noreturn))

typedef void (*AllocCont)( void * );

void NORETURN longjmp_on_return( AllocCont f, jmp_buf env, void *mem ) {
	f(mem);
	longjmp(env, 1);
}

void NORETURN alloc_and_call( AllocCont f, size_t size, jmp_buf env, char *parent_ptr ) {
	char ptr;
	if( parent_ptr == NULL || parent_ptr - &ptr < (ptrdiff_t) size ) {
		alloc_and_call(f, size, env, parent_ptr == NULL ? &ptr : parent_ptr);
	} else {
		longjmp_on_return(f, env, &ptr);
	}
}

void sls_alloc( size_t size, AllocCont f ) {
	jmp_buf env;
	if( setjmp(env) == 0 )
		alloc_and_call(f, size, env, NULL);
}

const char *message = "Hello World!";

void do_stuff( char *mem ) {
	strcpy(mem, message);
	printf("%s\n", mem);
}

int main() {
	sls_alloc(strlen(message) + 1, (AllocCont) do_stuff);
}