Re: glusterd crashes when synctask is used in conjunction with inner functions.

[Jeff Darcy <jdarcy@xxxxxxxxxx>]

OK, I couldn't resist.  I've attached an inner-function test program which
weakly confirms my theory.  If you run it with no arguments, the inner function
works.  If you run it with arguments, this causes the stack to be reused and
that seems to include the "thunk" I mentioned.  The result is a jump into
nowhere, followed by SIGSEGV or SIGILL (oddly I've seen both).  If it fails in
the outer-function-return case, I'll bet it fails with ucontext trickery too.

http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html
http://stackoverflow.com/questions/2929281/are-nested-functions-a-bad-thing-in-gcc

#include <stdio.h>

typedef void print_fn (void);

print_fn *my_print_fn;

void
outer (void)
{
        int outer_val = 0x5678;

        void
        inner (void)
        {
                printf("in inner function, result = 0x%x\n",outer_val);
        }


        printf("in outer function\n");
        inner();
        my_print_fn = &inner;
}

void
rewrite_stack (void)
{
        char junk[1024] = {0,};

        printf("rewriting stack\n");
}

int
main (int argc, char **argv)
{
        outer();
        if (argc > 1) {
                rewrite_stack();
        }
        (*my_print_fn)();
        return 0;
}