memory bug debugging

Hello hackers,

I'm fiddling around with the backend and have created a memory bug. I
guess I'm overriding a palloced chunk, but can't figure out where.

The backend's report is:

WARNING:  problem in alloc set MessageContext: req size > alloc size for
chunk 0x8383ca8 in block 0x83834a0

Investigating a little I have found out that chunk size is 8, but
requested size is: 1912602626  (more than 1GB???). This certainly
doesn't make sense.

What tools or debugging options exist to find memory leaks / overrides?
I've read the utils/mmgr/README, which leads me to the conclusion that I
cannot use valgrind or similar tools.

It would be very helpful to know what chunk it is, or better: where it
got allocated.

Thank you for your help

Markus