RFR: 8262913: KlassFactory::create_from_stream should never return NULL

[Harold Seigel]

On Tue, 9 Mar 2021 13:45:42 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> ClassFileParser.create_instance_klass cannot return NULL without a pending exception, it's called by 
>        klassFactory::create_from_stream who also cannot return NULL without a pending exception, it's called by
>        SystemDictionary::parse_stream and SystemDictionary::resolve_from_stream who also cannot return NULL without a pending exception.
> 
> I removed the NULL checks on returns from these 4 functions and either replaced them with an assert, or in cases that already had an unconditional indirection from the return value, just removed the null checks.
> 
> I wrote a test case to cover the case of testing st->buffer() == NULL which returned NULL from SystemDictionary::resolve_from_stream to show that this code path is not used. ClassFileStream constructor will set buffer() to the u1* input argument if it doesn't point to anything and will get a ClassFormatError.
> 
> Tested with tier1-3.

These changes look good!  One suggestion is to consider changing "getMessage().equals(" calls in the test to "getMessage().contains(". This may make the test more likely to continue passing if the exception message gets enhanced.
Thanks, Harold

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Marked as reviewed by hseigel (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2892