RFR 8189838: Stack overflow when computing upward projection of an intersection type with fbounds

[Vicente Romero]

looks good,

Vicente

On 10/26/2017 11:09 AM, Maurizio Cimadamore wrote:
> Hi,
> the patch fixes a bug in the logic for detecting fbounds loop in the 
> LVTI upward projection logic. Basically when we recurse projection on 
> a type-variable (upper) bound, we must keep track of the variable 
> somewhere, as the bound can contain the variable itself, and lead to 
> infinite loops.
>
> I was aware of the situation and the original code was already doing 
> something in this regard - however, the try/finally used to add/remove 
> the variable to the list of seen variables was too broad, and it ended 
> up also removing type-var in case of cycles, thus defeating the 
> purpose of the logic, at least in certain examples.
>
> I've rectified the logic so that now a variable is removed from the 
> list at the end of its projection _only_ if no cycle has been 
> detected. Also, when a cycle is indeed detected, we need to return 
> either Object or <null> depending on the projection kind.
>
> Webrev here:
>
> http://cr.openjdk.java.net/~mcimadamore/8189838/
>
> Cheers
> Maurizio
>