asserts in jdk coding (outside hotspot)

[David Holmes]

Hi Thomas,

On 1/06/2017 10:26 PM, Thomas Stüfe wrote:
> Hi David,
> 
> On Thu, Jun 1, 2017 at 2:09 PM, David Holmes <david.holmes at oracle.com 
> <mailto:david.holmes at oracle.com>> wrote:
> 
>     Hi Thomas,
> 
>     On 1/06/2017 7:20 PM, Thomas Stüfe wrote:
> 
>         Hi all,
> 
>         so, we have the hotspot asserts with all the niceties of our error
>         reporting. But these asserts are only accessible from within
>         hotspot coding.
> 
>         In the JDK, in a number of places, I see that we use the
>         standard posix
>         assert()(
>         http://pubs.opengroup.org/onlinepubs/009695399/functions/assert.html
>         <http://pubs.opengroup.org/onlinepubs/009695399/functions/assert.html>).
> 
>         This means that when we trigger the assert, we will only get a brief
>         message on stderr and a core, but no hs_err file.
> 
>         It also means that -XX:+CreateCoredumpOnCrash is ignored, so it
>         is not
>         possible to switch off those core dumps.
> 
>         This is unfortunate and also easy to fix. We do not even have to
>         call into
>         the hotspot to get hotspot asserts. We could just force a NULL
>         pointer
>         access or send ourselves a SIGILL or something. Anything which
>         triggers the
>         hotspot signal handling would be fine.
> 
>         What do you think?
> 
> 
>     Sending ourselves a fatal signal doesn't indicate what assertion
>     failed. The error handler won't know it was an assert, just a SEGV
>     or SIGILL
> 
>     ??
> 
>     David
> 
> 
> Sure. But in many cases this still would be preferable to just a core. 
> We'd get a hs-err file - admittedly with a Segv instead of an assert 
> message - but we have a callstack and could deduce the error from there.

I suppose we could do all the assert related printfs before sending the 
signal. The assertion info wouldn't be in the hs_err log, but at least 
it would be somewhere.

Anyway I'll leave this for core-libs folk to mull over.

Cheers,
David

> I am not saying that this is an ideal solution. Of course, a really good 
> solution may invoke the real hotspot assert or one might come up with a 
> way to transfer assert information (message, file, line etc) to the 
> hotspot error handler. E.g. store the assert message in a globally 
> visible char array one could resolve via dlsym to avoid having to add 
> link dependencies.
> 
> 
> ..Thomas
> 
> 
>         Kind Regards, Thomas
> 
>