Debugging CTFE

[Matthias Walter]

Koroskin Denis Wrote:

> On Tue, 17 Jun 2008 20:56:00 +0400, BCS <ao at pathlink.com> wrote:
> 
> > Reply to Koroskin,
> >
> >> On Tue, 17 Jun 2008 20:04:25 +0400, Matthias Walter
> >> <Matthias.Walter at st.ovgu.de> wrote:
> >>
> >>> Hello,
> >>>  I have written some compile time executable functions with D 1.0
> >>> which  work in runtime but hang (and allocate memory without end) at
> >>> compile-time. Is there a way to debug this further? Can one print
> >>> stuff  out? (Don't know if writefln works at compile-time, as I'm
> >>> using Tango)  Can I somehow get a stack trace of the functions
> >>> called?
> >>>  best regards
> >>> Matthias Walter
> >> You can use pragma(msg, "hello there!") to output some text at compile
> >> time.
> >>
> >
> > I don't /think/ that works for what is wanted:
> >
> > char[] CTFE()
> > {
> >    char[] c = "hello world",    for(;c.length >0; c=c[0..$-1])
> >       pragma(msg, c);
> >
> >    return c;
> > }
> >
> >
> > // not tested
> >
> >
> 
> You are right. But although it doesn't work (currently) for CTFE, it does  
> for templates:
> 
> template itoa(uint i)
> {
>      static if (i < 10)
>          const char[] itoa = "" ~ cast(char)(i + '0');
>      else
>          const char[] itoa = itoa!(i / 10) ~ itoa!(i % 10);
> }
> 
> template factorial(int i)
> {
>      pragma(msg, "Calculating factorial of " ~ itoa!(i));
> 
>      static if (i < 2) {
>          const int factorial = 1;
>      } else {
>          const int factorial = factorial!(i-1)*i;
>      }
> }
> 
> int main()
> {
>      const int t = factorial!(100);
>      return 0;
> }

Yes, the problem is, that compile-time functions must also be runtime-executable (and pragma must not depend on runtime variables), which I think, should not be a necessarity. But I guess this makes sense from Walters point of view, so this won't change in near future, I guess.