[U-Boot] gcc-4.6 warnings

Mike Frysinger
2011-08-25T21:58:14Z

On Thursday, August 25, 2011 17:44:58 Timur Tabi wrote:
> Mike Frysinger wrote:
> > if we let the optimizer do it instead of the preprocessor, we get better
> > code coverage in the face of different config settings.
>
> Oh, I thought this was some new feature of U-Boot.
>
> Can you give me an example of where DCE could be used to eliminate an
> #ifdef?

a change i talked about but havent yet posted would be to fix debug().
currently it looks more or less like:
#ifdef DEBUG
# define debug(...) printf(...)
#else
# define debug(...)
#endif
this causes people to do things like put local variables only used with
debug() code behind an #ifdef DEBUG in their code otherwise they get unused
variable warnings.

if, instead, we did something like:
#ifdef DEBUG
# define __DEBUG_KNOB 1
#else
# define __DEBUG_KNOB 0
#endif
#define debug(...) do { if (__DEBUG_KNOB) printf(...); } while (0)

the code would always get compiled and checked, but gcc would throw away it at
DCE time, and there would be no unused variable warnings.
-mike
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