RFR: 8312401: SymbolTable::do_add_if_needed hang when requesting length exceeds max_symbol_length

[David Holmes]

On Wed, 19 Jul 2023 20:18:01 GMT, Jiangli Zhou <jiangli at openjdk.org> wrote:

> Please review the simple fix to resolve infinite loop in SymbolTable::do_add_if_needed caused by extra long symbol string that exceeds Symbol::max_length(). See JDK-8312401 for details.
> 
> The jtreg test is converted from a test case constructed by @cushon.

> I considered changing to use char * for the message in java_lang_Throwable::create_initialization_error (https://github.com/openjdk/jdk/commit/e2223f0613d53e89e11af587dc3d41a25ffd6849). But we need to handle all other callers as well. Exceptions::log_exception can use char * also. The other callers still require Symbol.

Hmmm ... by using a Symbol we are artificially restricting the length of the exception message. That is fine if the VM is constructing the message, but not if the message can come from an external source as in this case. IIUC only `java_lang_Throwable::create_initialization_error` tries to use an existing, externally defined message, so only it should have this problem. So we either stop using a Symbol in this case (we copied the code from the resolution error case) or we handle the limitation - which to me means we should truncate so that we at least retain most of the potentially useful information. It seems unrealistic to have exception messages this large in non-tests. I'm not sure why we use Symbol here in the first place. @coleenp will know but is away this week.

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PR Comment: https://git.openjdk.org/jdk/pull/14938#issuecomment-1644919339