Debugging CTFE

Fawzi Mohamed fmohamed at
Wed Jun 18 02:43:12 PDT 2008

On 2008-06-17 19:42:33 +0200, BCS <ao at> said:

> Reply to Matthias,
>> 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
> Walter,can we plese get some debugging hooks in the CTFE stuff?

would be nice, actually a compile-time stacktrace upon failure is all I 
would need :)

anyway I had once the same problem, in my case it was something like this

class A(T,int i){
  A!(T,i+1) growI(int b){}

that forced the instantiation of A!(T,i+1) which in turn forced the 
instantiation of ...

moving the  function out of the class fixed the things
	A!(T,i+1) growI(T,int i)(A!(T,i)a,int b){}

In general I have found some very weird bugs (absence of this, getting 
tuck in some dependencies,...) with template member functions (that 
seem to be there in dmd since long), so when possible I use external 
templates, and limit the use of mixins.
Doing it it worked out quite well.


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