[Issue 5248] New: 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

           Summary: CTFE Segfault when calling a function on an enum
                    struct
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: gareth.tpc at gmail.com


--- Comment #0 from Gareth Charnock <gareth.tpc at gmail.com> 2010-11-21 14:28:54 PST ---
This code makes the DMD compiler segfault

struct LeafType {
    string Compile_not_ovloaded() {
        return "expression";
    }
};

struct MatrixASTNode {
    LeafType Right;

    string Compile() {
        return  Right.Compile_not_ovloaded();
    }
};

void main() {
    enum AST = MatrixASTNode();
    enum s=AST.Compile();
}


Inspecting dmd with a debugger suggests this is caused by a stack overflow.
These two functions in interpret.c call each other repeatedly.

Expression *ThisExp::interpret(InterState *istate)
{
    if (istate && istate->localThis)
        return istate->localThis->interpret(istate);
    error("value of 'this' is not known at compile time");
    return EXP_CANT_INTERPRET;
}

Expression *DotVarExp::interpret(InterState *istate)
{   Expression *e = EXP_CANT_INTERPRET;

#if LOG
    printf("DotVarExp::interpret() %s\n", toChars());
#endif

    Expression *ex = e1->interpret(istate); // <- we never get past here
     /* rest of function */
    }


If you turn logging on for the file you get this:

CallExp::interpret() MatrixASTNode(LeafType()).Compile()

********
FuncDeclaration::interpret(istate = (nil)) Compile
cantInterpret = 0, semanticRun = 5
StructLiteralExp::interpret() MatrixASTNode(LeafType())
StructLiteralExp::interpret() LeafType()
CompoundStatement::interpret()
ExpStatement::interpret(assert(&this,"null this"))
AssertExp::interpret() assert(&this,"null this")
StructLiteralExp::interpret() MatrixASTNode(LeafType())
StructLiteralExp::interpret() LeafType()
ReturnStatement::interpret(this.Right.Compile_not_ovloaded())
CallExp::interpret() this.Right.Compile_not_ovloaded()

********
FuncDeclaration::interpret(istate = 0xbfe685a0) Compile_not_ovloaded
cantInterpret = 0, semanticRun = 5
DotVarExp::interpret() this.Right
StructLiteralExp::interpret() MatrixASTNode(LeafType())
StructLiteralExp::interpret() LeafType()
CompoundStatement::interpret()
ExpStatement::interpret(assert(&this,"null this"))
AssertExp::interpret() assert(&this,"null this")
DotVarExp::interpret() this.Right
DotVarExp::interpret() this.Right
DotVarExp::interpret() this.Right
DotVarExp::interpret() this.Right
...an so on until stack overflow


The reason for the recursion happens is that in the context of
DotVarExp::interpret istate->localThis == this so in ThisExp::interpret the
statement

istate->localThis->interpret(istate);

goes right back to DotVarExp::interpret again.

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