[15] RFR(S): 8246203: Segmentation fault in verification due to stack overflow with -XX:+VerifyIterativeGVN

[Vladimir Kozlov]

I think the check should be 'verify_depth > 0' because verify_depth can be negative:

+  verify_depth--; // Visiting the first node on depth 1
+  bool add_to_worklist = verify_depth != 0;

Or it is intentional for negative value to visit all nodes? Then it needs comment.
In such case you need restore verify_depth == 0 check to return otherwise with 0 the code will work as with negative value:
   if (verify_depth == 0) {
     return;
   }
   bool add_to_worklist = true;

Or may be use assert(verify_depth != 0, "sanity") instead of check.

Thanks,
Vladimir

On 6/9/20 8:26 AM, Christian Hagedorn wrote:
> Hi
> 
> Please review the following patch:
> https://bugs.openjdk.java.net/browse/JDK-8246203
> http://cr.openjdk.java.net/~chagedorn/8246203/webrev.00/
> 
> The testcase creates a deep graph with a lot of nodes on a chain. When running with -XX:+VerifyIterativeGVN, it 
> recursively calls Node::verify_recur() for each input node discovered which eventually results in a segmentation fault 
> due to a stack overflow (around 10000 recursive calls due to such a long chain of nodes). The fix just converts the 
> recursive algorithm into an iterative one to avoid a segmentation fault.
> 
> Thank you!
> 
> Best regards,
> Christian