[FFmpeg-devel] [PATCH] libavcodec/wmavoice.c: local variablepow might mask pow function

[Axel Holzinger]

Hi Eli et al,

On Sun, Jul 25, 2010 at 9:41 PM, Eli Friedman wrote:
> On Sun, Jul 25, 2010 at 12:18 PM, Axel Holzinger 
> <aholzinger at gmx.de> wrote:
> > The issue is that a local variable pow masks a function pow 
> > and that hurts if powf - which is used in the scope of local 
> > variable pow - is not a function but a macro using double
> > precision pow function.
> 
> And I'm pointing out that such an implementation is not 
> correct per C99.

I read the standard and under 7.1.4 (1) it's stated that standard
headers may export function like macros. I don't see how this couldn't
be correct C99. Could you please provide a reference where it's stated
that a function like macro is forbidden in a standard header (at least
for powf)?

Also Unix/Posix allows powf to be implemented as a macro:
http://www.opengroup.org/onlinepubs/009695399/basedefs/math.h.html

> > Besides taking the effort to apply and document a patch, 
> > what do you think stands against the patch?
> 
> Simply that you haven't actually pointed to why this is 
> necessary other than the abstract possibility of a 
> non-conforming implementation of math.h.

As mentioned above, I can't see why such an implementation would be
non-conforming. Can you elaborate.

I think I did point out why this is important and together with the
above it's a potential problem that I tried to help to fix.

What is to say against a patch that

- doesn't add a single additional character
- doesn't change the structure of the code
- doesn't uglify the code
- does keep the variable naming in terms of being self explaining
- makes the code more widely usable

But there is another possibility: You could put the powf call in
parenthesis "using(powf)(...)" instead of "powf(...)". This would
prevent macro usage for powf.

But doesn't this uglify the code?

Regards
Axel