[PATCH v3 00/16] Fix signal-unsafe logging

[Chase Douglas]

On 04/16/2012 11:14 AM, Chase Douglas wrote:
> This new patchset has some large improvements:
> 
> * Variadic logging. This is done using preprocessor magic, so it is
>   incompatible with the current variadic logging. It is also not type-
>   safe (it could be with C11 _Generic, but only clang supports it so
>   far). It also only supports up to 10 arguments. If you pass more, bad
>   things might happen, but we can always increase the size as needed.
>   Due to these issues and formatting limitations, I don't think we
>   should switch all our logging to be signal-safe. We just have to be
>   more careful with signal-safe logging.
> 
>   The logging is now *printf-like. However, it only supports %s, %u, %x,
>   and %p (because it was trivial). I haven't see any need for %d, so I
>   didn't add it. No modifiers of any sort are supported, %u and %x are
>   extended to 64-bit values.
> 
>   The macro magic requires an ugly GCC pragma hack to turn off a
>   specific warning for when casting a pointer return value of a function
>   to a non-pointer value. I can't come up with a casting mechanism that
>   GCC likes for all scenarios, and we are admittedly doing horrible,
>   awful casting that normally would be verboten.
> 
> * Added ErrorSigSafe() macro and converted all the ErrorF signal logging
>   to it.
> 
> * Made BUG_WARN* signal safe.
> 
> * Use BUG_WARN_MSG() when logging unsafely in signal context. This logs
>   the full backtrace so it is even easier to find the offending message.
> 
> Unfortunately, I don't have time right now to get to unit testing. I
> must drop this work in order to get back to some Ubuntu release stuff.

I forgot again to mention that this can be found in a new branch on fdo:

http://cgit.freedesktop.org/~cndougla/xserver/log/?h=signal-logging2

-- Chase