RFR: 8271003: hs_err improvement: handle CLASSPATH env setting longer than O_BUFLEN

[David Holmes]

On 2/08/2021 6:26 pm, Thomas Stuefe wrote:
> On Mon, 2 Aug 2021 07:02:35 GMT, David Holmes <dholmes at openjdk.org> wrote:
> 
>> `outputStream::do_vsnprintf` already states that it uses the buffer "if necessary". In the two highlighted cases there is no need to use the buffer, so I would argue that we should just modify the existing `outputStream::do_vsnprintf` logic to not truncate in these two cases as it is not necessary.
> 
> I think we already do almost that.
> 
> https://github.com/openjdk/jdk/blob/95f0fd6c4dfaea9c3e065485dd201decf2be98ba/src/hotspot/share/utilities/ostream.cpp#L94-L104
> 
> Only thing, for print_cr() we still use the scratch buffer since we need to append \n. That could be done smarter.

Right I missed that bit - but I guess we can do that as a separate 
write() call.

> Beyond that, I think the O_BUFLEN thing is seriously annoying and I would like to have a better solution. One where we start with a preallocated buffer as we do now, but expand it dynamically (using raw ::malloc()) if necessary. That should still be reasonably safe.

Raw malloc in the error handler is not safe if we're processing a 
signal. The malloc/signal deadlock is already seen with some of our 
abort tests.

Cheers,
David

> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/4947
>