Re: Pools rewrite [2]

[Greg Marr]

At 11:44 AM 12/05/2001, Brian Pane wrote:
Aaron Bannert wrote:
On Wed, Dec 05, 2001 at 12:35:00PM +0100, Sander Striker wrote:
<comment>
Ack.  No.  Declare a new scope like so:
#define UNLOCK(mutex) \
 do { \
   if (mutex) \
       apr_thread_mutex_unlock(mutex); \
 } while(0)
Calling it like UNLOCK(mutex) (i.e. no semicolon) is just badness
and will shoot us down the road later.
</comment>
Ok, will change that.
If the semicolon is the only problem, just remove the semicolon from
the macro:
#define UNLOCK(mutex) \
   if (mutex) \
       apr_thread_mutex_unlock(mutex)
I recommend still creating a scope around the if-statement:
#define UNLOCK(mutex) \
 { \
     if (mutex) \
         apr_thread_mutex_unlock(mutex); \
 }
That will guard against unintended effects when the macro
is used in code like this:
   if (condition)
     UNLOCK(mutex)
   else
     ...
That will fail if it's called like this:
if (condition)
    UNLOCK(mutex);
else
    ...
since it will expand to:
if (condition)
    {
    if (mutex)
        apr_thread_mutex_unlock(mutex);
    };
else
    ...
Note the ; after the close brace, that makes the else illegal.
The only truly safe construct that I've seen is the do/while 
recommended above.

--
Greg Marr
[EMAIL PROTECTED]
"We thought you were dead."
"I was, but I'm better now." - Sheridan, "The Summoning"