RFR: 8358706: Integer overflow with -XX:MinOopMapAllocation=-1

[Paul Hübner]

On Mon, 1 Dec 2025 14:00:22 GMT, Casper Norrbin <cnorrbin at openjdk.org> wrote:

> Hi everyone,
> 
> Passing a negative value to `-XX:MinOopMapAllocation` could trigger an integer overflow. This value is used as the initial size for the `OopMap` `GrowableArray` list inside `OopMapSet`. Negative inputs hits an assert when allocating for `GrowableArray`. Restricting this flag to positive values ensures we get a clear error message instead of a crash.
> 
> Testing:
> - Oracle tier 1
> - Local tests with `-XX:MinOopMapAllocation=x`, covering both valid and invalid values.

src/hotspot/share/runtime/globals.hpp line 1674:

> 1672:                                                                             \
> 1673:   /* new oopmap storage allocation */                                       \
> 1674:   develop(intx, MinOopMapAllocation,     8,                                 \

Shouldn't we also make this an `int` while we're at it since a `GrowableArray`'s length is kept as an `int`?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28576#discussion_r2577252382