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
