RFR: JDK-8325530: Vague error message when com.sun.tools.attach.VirtualMachine fails to load agent library [v3]

[Alex Menkov]

On Thu, 22 Feb 2024 22:27:04 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> In invoke_Agent_OnAttach(), I think the second print_cr() should start with a space:
> 
> ```
>       st->print_cr("%s was not loaded.", agent->name());
>       if (*ebuf != '\0') {
>         st->print_cr("%s", &ebuf[0]);
>       }
>       return false;
> ```
> 
> Otherwise in the output you see the reason for the failure start right after the period:
> 
> `com.sun.tools.attach.AgentLoadException: Failed to load agent library: FailedLoadAgentTestNotExists was not loaded.libFailedLoadAgentTestNotExists.so: cannot open shared object file: No such file or directory`

It may be other messages in the outputStream (like "Dynamic agent loading is not enabled.")
So I think it should be fixed in HotSpotVirtualMachine.readErrorMessage (it converts multi-line message to single string) by replacing CRs with spaces.

> 
> Also, ebuf is of size 1024 and is getting truncated sometimes. See your macosx log files on mdash. This doesn't necessarily have to be fixed, but something to consider.

I'll file a separate issue for this.

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PR Comment: https://git.openjdk.org/jdk/pull/17954#issuecomment-1960504459