RFR: 8329581: Java launcher no longer prints a stack trace [v4]

[Mandy Chung]

On Tue, 23 Apr 2024 18:21:42 GMT, Sonia Zaldana Calles <szaldana at openjdk.org> wrote:

>> Hi folks, 
>> 
>> This PR aims to fix [JDK-8329581](https://bugs.openjdk.org/browse/JDK-8329581). 
>> 
>> I think the regression got introduced in [JDK-8315458](https://bugs.openjdk.org/browse/JDK-8315458). 
>> 
>> In the issue linked above, [LauncherHelper#getMainType](https://github.com/openjdk/jdk/pull/16461/files#diff-108a3a3e3c2d108c8c7f19ea498f641413b7c9239ecd2975a6c27d904c2ba226) got removed to simplify launcher code.
>> 
>> Previously, we used ```getMainType``` to do the appropriate main method invocation in ```JavaMain```. However, we currently attempt to do all types of main method invocations at the same time [here](https://github.com/openjdk/jdk/blob/master/src/java.base/share/native/libjli/java.c#L623). 
>> 
>> Note how all of these invocations clear the exception reported with [CHECK_EXCEPTION_FAIL](https://github.com/openjdk/jdk/blob/140f56718bbbfc31bb0c39255c68568fad285a1f/src/java.base/share/native/libjli/java.c#L390). 
>> 
>> Therefore, if a legitimate exception comes up during one of these invocations, it does not get reported. 
>> 
>> I propose reintroducing ```LauncherHelper#getMainType``` but I'm looking forward to your suggestions. 
>> 
>> Cheers, 
>> Sonia
>
> Sonia Zaldana Calles has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Changes based on feedback

I missed that `NULL_CHECK0` prints that JNI error, sorry.  We should avoid using it then.   What do you think having a check macro to return 0 if exception occurred or the given object is null?   No exception cleared as it will be described in JavaMain.


#define CHECK_EXCEPTION_NULL_FAIL(obj) \
    do { \
        if ((*env)->ExceptionOccurred(env)) { \
            return 0; \
        } else if (obj == NULL) { \
            return 0; \
        } \
    } while (JNI_FALSE)

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PR Comment: https://git.openjdk.org/jdk/pull/18786#issuecomment-2073184282