[Webkit-unassigned] [Bug 39893] Explicitly use PTHREAD_MUTEX_NORMAL to create pthread mutex

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=39893


Darin Adler <darin at apple.com> changed:

           What    |Removed                     |Added
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  Attachment #57462|review?                     |review-
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--- Comment #16 from Darin Adler <darin at apple.com>  2010-05-31 10:01:25 PST ---
(From update of attachment 57462)
> +    // Make sure it's not the same value as PTHREAD_MUTEX_INITIALIZER.
> +    memset(&m_mutex, 0, sizeof(pthread_mutex_t));

If we are doing this memset, I think it's better style to call sizeof(m_mutex) here instead of sizeof(pthread_mutex_t), because that way you can see looking at this line of code that it's correct without having to look up the type of m_mutex to double check that it's a pthread_mutex_t.

As I said in my previous comment in this bug, this comment and code are not needed, and I am almost certain the comment reflects a misunderstanding on your part. I don't want to confuse future programmers working on this code.

Initializing to zero does have a small good effect. It gives us more predictable behavior if pthread_mutex_init fails. Both the old code path and the new code path have the same failing in that they don't check the error return of pthread_mutex_init. But this issue is not specific to this new code path and applies just as much to the PTHREAD_MUTEX_NORMAL == PTHREAD_MUTEX_DEFAULT case.

Despite the fact that this patch is otherwise just fine, I'm going to say review- because I don't want to check in a mysterious comment or unneeded code.

The only difference between the two branches of the #if should be the attributes passed in to pthread_mutex_init.

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