Integrated: 8343531: Improve print_location for invalid heap pointers

[Volker Simonis]

On Mon, 4 Nov 2024 09:43:18 GMT, Volker Simonis <simonis at openjdk.org> wrote:

> Currently `BlockLocationPrinter<CollectedHeapT>::print_location()` checks for a pointer if it points into the heap and if that's true, it either prints it as an oop if `is_valid_obj()` is true or it tries to find the the start address of an oop for that pointer by calling `CollectedHeapT::heap()->block_start()`.
> 
> However, the `block_start()` functionality is not fully implemented for all GCs (e.g. the young generation of `ParallelScavengeHeap`) and for these cases `block_start()` returns NULL. Because of this NULL return value `os::print_location()` will finally qualify the corresponding pointer as pointing "into unknown readable memory" although we already know that it actually points into an invalid heap area.
> 
> In such cases, print at least that the pointer is pointing into an unknown part of the heap instead of just saying that it points into unknown memory. 
> 
> I've manually tested the new functionality in GDB.

This pull request has now been integrated.

Changeset: f0b251d7
Author:    Volker Simonis <simonis at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/f0b251d76078e8d5b47e967b0449c4cbdcb5a005
Stats:     8 lines in 1 file changed: 6 ins; 0 del; 2 mod

8343531: Improve print_location for invalid heap pointers

Reviewed-by: shade, tschatzl, ayang

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PR: https://git.openjdk.org/jdk/pull/21870