__FILE__ and __LINE__ again...

[Paolo Invernizzi]

On Tuesday, 10 September 2013 at 16:45:33 UTC, H. S. Teoh wrote:
> On Tue, Sep 10, 2013 at 06:00:53PM +0200, Paolo Invernizzi 
> wrote:
>> Johannes Pfau wrote something like this, in the logger thread:
>> 
>> >If you write code like this:
>> >
>> >void log(string file = __FILE__)() //A template
>> >{
>> >  logImpl(file);
>> >}
>> >void logImpl(string file){} //Not a template
>> >
>> >The compiler can always inline the log template. So there's no
>> >template bloat as there will be effectively no instances of 
>> >log.
>> >Instead it will be inlined and logImpl will be called directly
>> >just as if you manually called logImpl(__FILE__).
>> 
>> I'm trying something like that, but with __LINE__ in addition 
>> to put
>> a little more pressure:
>> 
>>     void log(string file = __FILE__, int line = __LINE__)(){
>> logImpl(file, line); }
>>     void logImpl(string file, int line){}
>> 
>> I've then compiled a single file filled with 'log()', but I've 
>> found
>> from 'nm' that the text section is still full of templated
>> functions.
>> 
>> So the question is: is Johannes trick supposed to work, or 
>> there's
>> something I don't understand well about template expansion and
>> inlining?
> [...]
>
> Did you compile with dmd -inline?
>
> Having said that, if you don't have variadic arguments, 
> __FILE__ and
> __LINE__ should be default arguments at the end of the *runtime*
> argument list. Runtime arguments should be used to prevent 
> template
> bloat:
>
> 	void log(/* other arguments here */, string file=__FILE__, int 
> line=__LINE__)
> 	{
> 		...
> 	}
>
> If you have variadic arguments, though, this wouldn't work.
>
> In any case, if the template function is just a thin wrapper 
> around
> logImpl, and you're compiling with -inline, then there should 
> be no
> runtime overhead. The compiler will still emit template 
> instantiations
> for each call to log(), but you can get rid of this with 
> link-time
> optimization (on Posix, you'd add -L-gc-sections to your dmd
> command-line: this will cause ld to delete code sections that 
> are never
> referenced, which includes the log() instantiations if indeed 
> they have
> been inlined).
>
>
> T

Thank you to everybody,

As you can guess, I would like to have variadic arguments: I'll 
try to investigate if some mixin syntax is not too horrible to be 
use...

/Paolo