Re: [bug #18217] glibc: `__libc_once'

[Barry deFreese]

Thomas Schwinge wrote:
> Follow-up Comment #2, bug #18217 (project hurd):
>
> Roland: ``Uli abused the macros.  To support the use he wants, __libc_once
> should be revamped in all its implementations to return a value or have a
> variant that does (value says whether fn just ran).''
>
>   
Is there any reason this wouldn't work?

Current code:

/* Use mutexes as once control variables. */

struct __libc_once
 {
   __libc_lock_t lock;
   int done;
 };

#define __libc_once_define(CLASS,NAME) \
 CLASS struct __libc_once NAME = { MUTEX_INITIALIZER, 0 }

/* Call handler iff the first call.  */
#define __libc_once(ONCE_CONTROL, INIT_FUNCTION) \
 do 
{                                                                        \
   __libc_lock_lock 
(ONCE_CONTROL.lock);                                     \
   if 
(!ONCE_CONTROL.done)                                                   \
     (INIT_FUNCTION) 
();                                                     \
   ONCE_CONTROL.done = 
1;                                                    \
   __libc_lock_unlock 
(ONCE_CONTROL.lock);                                   \
 } while (0)

Change to:

*Remove struct

#define __libc_once_define(CLASS,NAME) \
   CLASS int NAME = MUTEX_INITIALIZER

/* Call handler iff the first call.  */
#define __libc_once(ONCE_CONTROL, INIT_FUNCTION) \
   do {
     __libc_lock_lock(ONCE_CONTROL);
     if ((ONCE_CONTROL) == MUTEX_INITIALIZER)
       (INIT_FUNCTION)();
     ONCE_CONTROL = 1;
     __libc_lock_unlock(ONCE_CONTROL);
   } while (0)

Or am I waaay off as usual?

Thanks!

Barry deFreese (aka bddebian)