segfault

[spir]

On Thu, 11 Nov 2010 15:11:34 -0500
"Steven Schveighoffer" <schveiguy at yahoo.com> wrote:

> > As you see, the addresses of the 2 sub-patterns have changed (but the  
> > array that holds them hasn't moved -- and I just checked that  
> > cast(void*)array actually returns the ptr). Don't know what to conclude.
> >  
> 
> OK, can we see the code for Tuple?  That may be where something fishy is  
> occurring.

Well, since the pattern is OK _after_ call to Tuple's constructor (which does nothing more than recording its sub-patterns, see below) and only gets wrong when qutting this(), I fail to see how Tuple could be cause of anything. Also, the corruption is visible _before_ calling match() (which here delegates to Tuple's check()).

I understand your note about returning an object actually allocated on the stack -- but here there are only implicitely referenced objects (class instances). This would mean that D creates the 2 sub-patterns on the stack? But why those objects, precisely? (Also note that they are of different classes: one is here a "String", the other a "ZeroOrMore"). They are stored in an array.

What's troubling is that the array elements, meaning the supposed subpattern addresses, have changed. Maybe the patterns themselves are still ok, but the array data only are corrupted?
Oh, I may try to cast to String the memory area pointed inside this()....... Does not seem to work: I recorded the pointer read in this() (as String*) into a global; then in the test func:
    writeln("p: ",p);       	// ok, same address as in this()
    writeln(cast(String)(*p));	// segfault!

Anyway, just in case my reasoning is wrong, here is the whole Tuple class:

====================================================
class Tuple : Pattern {
    /**  pattern type for tuple of given patterns */
    static string typename = "Tuple";
    Pattern[] patterns;
    this (Pattern[] patterns...) {
        this.patterns = patterns;
    }
    // operational
    override Result check (Source source) {
        /**  Check whether text holds successive matches of all patterns. */
        // try & match
        // case success: rest text slice is given by each match result
        // case failure: MatchFailure error is thrown by sub-pattern
        Node[] nodes;
        Result result;
        foreach (Pattern pattern ; patterns) {
            result = pattern.check(source);
            nodes ~= result.node;
            source = result.source;
        }
        auto node = new TupleNode(this, nodes);
        return new Result(node, source);
    }
    // feedback
    override string toString () {
        /** "(p1 p2 ...)" */
        return listText!Pattern(this.patterns, " " ,"(",")");
    }
}


Denis
-- -- -- -- -- -- --
vit esse estrany ☣

spir.wikidot.com