RFR: 8335610: DiagnosticFramework: CmdLine::is_executable() correction

[David Holmes]

On Wed, 3 Jul 2024 13:58:51 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

> CmdLine::is_executable() looks wrong, surely an empty line is not executable.
> 
> With this change, in DCmd::parse_and_execute() we will avoid needlessly entering the code block to try and execute the command.
> 
> DCmd tests all good:
> make images test TEST="test/hotspot/jtreg/serviceability/dcmd test/jdk/sun/tools/jcmd"

My concern is that the logic was wrong and so you fixed it, but this then screams out for a test that would have detected the error, but you can't write a test because the line can never be empty, so that becomes an invariant rather than a runtime check.

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PR Comment: https://git.openjdk.org/jdk/pull/20006#issuecomment-2209631591