[Ffmpeg-devel] [PATCH] move utf8 writing to libavutil

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> Hi
>
> On Sat, Jul 08, 2006 at 08:56:18PM +0100, M?ns Rullg?rd wrote:
>> Justin Ruggles <jruggle at earthlink.net> writes:
>> 
>> > Please explain the benefit of the do/while. What does it protect against?
>> 
>> Without it,
>> 
>> if(whatever)
>>     PUT_UTF8(...);
>> 
>> will have some quite unintended results without so much as a warning.
>> 
>> The idea with a do { } while(0) construct is to turn the entire macro
>> body into a single statement while still keeping the semicolon
>> (usually) placed after the macro invocation part of this same
>> statement.  Simply enclosing the body in braces will make the final
>> semicolon form a new, empty statement, which will break things like
>> 
>> if(foo)
>>     PUT_UTF8(...);
>> else
>>     PUT_UTF8(...);
>
> the intended use of thet GET/PUT_UTF8 macros was so that each application
> could easily build their own utf8 reading and writing functions with their
> own get_bits / put_bits system

That may well be, but I still think multi-statement macros should have
a do { } while(0) just in case.  It can avoid some nasty and hard to
find errors, and it has no negative effects.

-- 
M?ns Rullg?rd
mru at inprovide.com