Question

I have a pointer in GDB, how can I find out where it was first allocated on the heap?

In WinDBG, this can be done by !heap -p -a <0x12345678> after turning on gflags /i <*exe> +ust

Since Valgrind can tell me where the memory is allocated (when it detects some leaks), I guess this is also possible?

(This is NOT about watchpoint. This is given the situation where I randomly break into the In GDB, application, look at a pointer and want to know “who created this piece of memory”?)

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Using reverse debugging in GDB is a very novel way and probably the correct way to solve this problem. I encountered some problem with that approach with GDB 7.1 — the latest stable version. Reverse debugging is a rather new feature in GDB so I needed to check out HEAD (7.2) to fix it.

It probably says something about the matureness of the GDB approach but I think it should definitely be used when it’s more mature. (Awesome feature!)

Answer 1

Valgrind hijacks memory management calls, that’s how heap checkers work. There’s no facility in GDB itself to tell you where given address was returned by malloc(3). I suggest looking into mtrace and glibc allocation debugging.