[Issue 5248] CTFE Segfault when calling a function on an enum struct

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=5248


Don <clugdbug at yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |clugdbug at yahoo.com.au


--- Comment #3 from Don <clugdbug at yahoo.com.au> 2011-01-16 12:20:07 PST ---
Excellent!

(In reply to comment #2)
> Okay, had time for a little more poking. Execution moves to
> DotVarExp::interpret and the endless loop from here:
> 
> 
> Expression *AssertExp::interpret(InterState *istate)
> {   Expression *e;
>     Expression *e1;
> 
>     if( this->e1->op == TOKaddress)
>     {   // Special case: deal with compiler-inserted assert(&this, "null this")
>         AddrExp *ade = (AddrExp *)this->e1;
>         if (ade->e1->op == TOKthis && istate->localThis)
>             if (ade->e1->op == TOKdotvar  // <--- something is fishy here
>                 && ((DotVarExp *)(istate->localThis))->e1->op == TOKthis)
>                 return getVarExp(loc, istate,
> ((DotVarExp*)(istate->localThis))->var);
>             else
>                 return istate->localThis->interpret(istate);
>     }
> 
> Apparently the compiler puts in an implicit assert(&this,"this is null") at the
> beginning of member functions.
> 
> Now ade->e1->op == TOKthis is true by the time execution reaches the inner if
> so why is ade->e1->op == TOKdotvar being tested? That statement is always
> false. If we replace ade->e1->op == TOKdotvar with true the compiler accepts
> the sample program.

> 
> The question is, what is getVarExp? and why might return
> istate->localThis->interpret(istate); be the wrong thing to do?

If it is returning by reference, it needs to return a VarExp, whereas
localThis->interpret() returns the value of 'this' (ie, an rvalue).

You're right about the problem line. That should definitely be:

-             if (ade->e1->op == TOKdotvar
+             if (istate->localThis->op == TOKdotvar
                 && ((DotVarExp *)(istate->localThis))->e1->op == TOKthis)
                 return getVarExp(loc, istate,

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