RFR: 8367149: Add convenient construction for creating ad-hoc VMErrorCallback [v5]
Axel Boldt-Christmas
aboldtch at openjdk.org
Fri Oct 3 08:17:50 UTC 2025
> 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.
Axel Boldt-Christmas has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
- Merge tag 'jdk-26+18' into JDK-8367149
Added tag jdk-26+18 for changeset 5251405c
- Merge tag 'jdk-26+17' into JDK-8367149
Added tag jdk-26+17 for changeset 2aafda19
- Replace ergonomic with convenient
- Add a comment explaining the deduction rules
- Skip multiple inheritance and allow more than lambda like callables.
- Update doc example
- 8367149: Add ergonomic construction for creating ad-hoc VMErrorCallback
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/27159/files
- new: https://git.openjdk.org/jdk/pull/27159/files/f2f3a1c1..250f23f3
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=27159&range=04
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=27159&range=03-04
Stats: 11978 lines in 389 files changed: 6399 ins; 3203 del; 2376 mod
Patch: https://git.openjdk.org/jdk/pull/27159.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/27159/head:pull/27159
PR: https://git.openjdk.org/jdk/pull/27159
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