RFR: 8271356: Modify jdb to treat an empty command as a repeat of the previous command [v3]

[Jakob Cornell]

On Tue, 31 Aug 2021 00:36:51 GMT, Jakob Cornell <github.com+5642931+jakobcornell at openjdk.org> wrote:

>> This has been under discussion on and off for the past month or so on serviceability-dev, and I think a CSR request is required, so this may be a work in progress.
>> 
>> Notes on the patch:
>> 
>> - The `list` command previously marked a line in each listing with `=>`.  In a bare `list` this is the next line up for execution.  Previously when requesting a specific location (e.g. `list 5`) the requested line would be marked.  With the patch applied, `list` will only ever mark the next line up for execution.  This is consistent with the behavior of GDB and PDB (at least).
>> - `EOF` is printed when the repeat setting is on and a bare `list` command follows a listing containing the last source line.  This feature is from PDB; it's a somewhat softer message than the one for an explicit `list` request that's out of range.
>> - I don't speak Chinese or Japanese, so I've omitted localizations for the new messages in those locales.  However, I updated the help text in both to include the new commands, with the descriptions left empty for now.
>
> Jakob Cornell has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

I think the main reason the diff was so unhelpful is that part of my original change was converting the `<n> <command>` handling from recursive to iterative.  I think the code as a whole is more intuitive when this is done iteratively, and along with the iterative approach came a fix (for synchronous commands) for a minor bug in which the prompt is printed along with each iteration of an `<n> <command>` command.

However, reverting to the recursive approach and restoring some original variable names has made the diff much easier to understand.  I do have the iterative version saved on a local branch in case it becomes useful.

I've run the tests you indicated (`make run-test-vmTestbase_nsk_jdb`) and those are all passing.  I'll take a look into writing some new tests for the changes.

I think the main reason the diff was so unhelpful is that part of my original change was converting the `<n> <command>` handling from recursive to iterative.  I think the code as a whole is more intuitive when this is done iteratively, and along with the iterative approach came a fix (for synchronous commands) for a minor bug in which the prompt is printed along with each iteration of an `<n> <command>` command.

However, reverting to the recursive approach and restoring some original variable names has made the diff much easier to understand.  I do have the iterative version saved on a local branch in case it becomes useful.

I've run the tests you indicated (`make run-test-vmTestbase_nsk_jdb`) and those are all passing.  I'll take a look into writing some new tests for the changes.

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PR: https://git.openjdk.java.net/jdk/pull/5290