RFR: 8367149: Add ergonomic construction for creating ad-hoc VMErrorCallback [v2]
Axel Boldt-Christmas
aboldtch at openjdk.org
Wed Sep 10 14:17:42 UTC 2025
> Add a class OnVMError which uses the VMErrorCallback mechanism which is an ergonomic 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 incrementally with three additional commits since the last revision:
- Add a comment explaining the deduction rules
- Skip multiple inheritance and allow more than lambda like callables.
- Update doc example
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/27159/files
- new: https://git.openjdk.org/jdk/pull/27159/files/a4ab0e3e..a4fb3397
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=27159&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=27159&range=00-01
Stats: 18 lines in 1 file changed: 11 ins; 0 del; 7 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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