[PATCH 6/7] Protect 'orig_len' in |recover_unused_bytes| by DBUS_ENABLE_VERBOSE_MODE

[Thomas Zimmermann]

Hi!

Some thoughts on this problem: with gcc, one can do something like this:

#ifndef DEBUG
  __dbus_assert (condition)
	do {
		__typeof (!(condition)) val __attribute__((__unused__));
	} while (0)
#else
  // do debug
#endif

This should use the type of 'condition' without evaluating it. The
declared variable itself is unused. Unfortunately I don't know how to do
this with _dbus_verbose's VA args.

Maybe additional annotation can be used, like

#define DEBUG_OR(expression, default_value) \
	(DEBUG ? expression : default_value)

and called like this:

my_debug_value = DEBUG_OR(compute_val(), 0);

Here DEBUG is evaluated by the C compiler, so compute_val() doesn't have
to protected by DEBUG-based preprocessor guards.

Best regards
Thomas

Am 15.08.2016 um 13:17 schrieb Simon McVittie:
> On 10/08/16 16:08, Thiago Macieira wrote:
>> One way I've solved this problem is to "use" the expression in even disabled 
>> asserts
> 
> That results in the expression's side-effects still happening: for
> instance if it calls a function, we pay the CPU cost of calling that
> function. I don't think we want that here.
> 


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