Integrated: 8367149: Add convenient construction for creating ad-hoc VMErrorCallback

[Axel Boldt-Christmas]

On Tue, 9 Sep 2025 06:26:32 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Add a class OnVMError which uses the VMErrorCallback mechanism which is a convenient construction for creating ad-hoc VMErrorCallback which automatically calls the provided invocable f if a VM crash occurs within its lifetime. Can be used to instrument a build for more detailed contextual information gathering. Especially useful when hunting down intermittent bugs, or issues only reproducible in environments where access to a debugger is not readily available. Example use:
> ```C++
>   {
>     // Note the lambda is invoked after an error occurs within this thread,
>     // and during on_error's lifetime. If state prior to the crash is required,
>     // capture a copy of it first.
>     auto important_value = get_the_value();
> 
>     OnVMError on_error([&](outputStream* st) {
>       // Dump the important bits.
>       st->print("Prior value: ");
>       important_value.print_on(st);
>       st->print("During crash: ")
>       get_the_value().print_on(st);
>       // Dump whole the whole state.
>       this->print_on(st);
>     });
> 
>     // Sometimes doing a thing will crash the VM.
>     do_a_thing();
>   }
> 
> 
> C++17 class template argument deduction finally makes these sort of constructions ergonomic to use without the need for auto and helper construction methods.

This pull request has now been integrated.

Changeset: d570765e
Author:    Axel Boldt-Christmas <aboldtch at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/d570765e2720a11c88c806554df9b13587a041a2
Stats:     48 lines in 1 file changed: 48 ins; 0 del; 0 mod

8367149: Add convenient construction for creating ad-hoc VMErrorCallback

Reviewed-by: ayang, stefank

-------------

PR: https://git.openjdk.org/jdk/pull/27159