Re: OSS sound

Rob Crittenden wrote:

>>>It also seems strange to go thru the trouble of a while loop that will always
>>>be false...
>>>
>>
>>It's a standard C idiom to make macros look like functions. Once can 
>>write CLEAR_OMR(parm); in the code (note semicolon)
> 
> 
> Yes, I understand how macros work. My question is why have a do/while loop that
> will always exit at the first test? Why not write the macros as:
> 
> ...
> #define CLEAR_OMR(omr) { int x = 0; read((omr)->msg_pipe[0], &x, sizeof(x)); }
> #define RESET_OMR(omr) { } 
> ...

Your suggestion would break code such as:
     if (...)
         CLEAR_OMR(omr);
     else
         ...;

The compiler would produce a syntax error at the "else" keyword.

See why?  It might help to look at the expansion of the above code 
(reindented and commented for clarity):

     if (...)
     {
         int x = 0;
         read((omr)->msg_pipe[0], &x, sizeof(x));
     } /* if statement ends here */

     ; /* empty statement */

     else /* error: else occurs without a matching if */
         ...;

Regards,
Luke.



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