RFR (S) 8217879: hs_err should print more instructions in hex dump

[Aleksey Shipilev]

On 1/29/19 6:13 AM, David Holmes wrote:
> so by increasing the size of the block you are potentially greatly increasing the risk that you will
> do something unsafe. Perhaps, as Thomas suggested, if you really want to expand this range it should
> be done in a more safe manner.

SafeFetch-based probing implemented here:
  http://cr.openjdk.java.net/~shade/8217879/webrev.03/

When you hack the code to pass pc=NULL, it would print:

Instructions: (pc=0x0000000000000000)
Memory is not readable

> I'm also very much in favour of the slimmer hs_err file. At this rate of expansion the hs_err file
> will look more like a core file, and we already have core files for that. ;-) hs_err files were
> never intended to be a one-stop debugging shop.

I don't know what your users submit on JVM crashes, but for us the availability of the core dump is
an exception rather than the rule. Most of the time all we have is hs_err. Having a little bit more
context does help figuring out what went wrong.

-Aleksey