commit 16adc58e73f3 (stdlib: Fix data race in __run_exit_handlers [BZ #27749])

[Rasmus Villemoes <rasmus.villemoes@prevas.dk>]

I think the commit in $subject is broken. I was browsing through the
atexit handling code and stumbled on something which is always a code
smell, namely the pattern

  if (whatever)
    continue;

at the end of a loop.

And indeed, since we no longer jump back to the outer loop and refetch
the list head, one can observe a change in behavior. This program:

#include <stdio.h>
#include <stdlib.h>

void h(void)
{
	printf("third: %s()\n", __func__);
}
void j(void)
{
	printf("second: %s()\n", __func__);
}

void g(void)
{
	printf("first: %s()\n", __func__);
	atexit(h);
	atexit(j);
}
void f(void) {
	static int c;
	printf("%s: %d\n", __func__, ++c);
}

int main(int argc, char *argv[])
{
	int i;

	/*
	 * Stuff the "struct exit_function_list" with dummy callbacks;
	 * 30 may need to be adjusted depending on how many atexit()
	 * registrations libc itself does.
	 */
	for (i = 0; i < 30; ++i)
		atexit(f);

	/* Register one more, to fill the last slot in struct
exit_function_list. */
	atexit(g);
	
	return 0;
}

used to print

first: g()
second: j()
third: h()
f: 1
...
f: 30

but now it instead prints

first: g()
third: h()
f: 1
...
f: 30
second: j()


Rasmus