[PATCH] hdparm new option parsing

[Rob Landley]

On Friday 05 May 2006 8:22 pm, Tito wrote:
> On Friday 5 May 2006 23:16, Rob Landley wrote:
> > What does the "#define PARSE_OPTS_CMD_V2 parse_opts_v2" accomplish,
> > exactly?
>
> It does the same as
>
> #if ENABLE_FEATURE_HDPARM_SOMETHING
> 	parse_opts_v2(x,y,z);
> #endif

A normal if:

  if (ENABLE_FEATURE_HDPARM_SOMETHING) parse_opts_v2(x,y,z);

Should optimize out when the enable macro is a constant 0.  So we can use 
normal C syntax and have everything checked for validity by the compiler (and 
thus not get surprised by build breaks when we toggle a configuration 
symbol).

Alas, sometimes you can't do that because, variables are only conditionally 
defined (generally structure members), or a function takes a variable number 
of arguments depending on how the config symbols go, and then you can use:

  USE_FEATURE_HDPARM_SOMETHING(parse_opts_v2(x,y,z);)

Which has the advantage that the knowledge is localized (the use site is where 
the decision whether or not to include the functionality is expressed), but 
without the line-based preprocessor syntax.  It works well with automatic 
string concatenation as well.  I.E. "thing" "also" becomes "thingalso", thus 
you can do "thing" USE_ALSO("also")

Rob
-- 
Never bet against the cheap plastic solution.