[Patch, libjava] use -fnon-call-exceptions rather than -fasynchronous-unwind-tables.

[Andrew Haley]

On 08/18/2010 04:08 PM, Richard Henderson wrote:
> On 08/18/2010 02:45 AM, Jakub Jelinek wrote:
>> On Wed, Aug 18, 2010 at 11:40:15AM +0200, Richard Guenther wrote:
>>> On Wed, Aug 18, 2010 at 11:30 AM, IainS
>>> <developer@sandoe-acoustics.co.uk> wrote:
>>>> IIUC, the following should be the 'correct' approach.
>>>> OK for trunk? (with an appropriate changelog,  of course).
>>>> Iain
>>>
>>> That doens't match what the comment says.  What is it the correct
>>> approach for?
>>
>> Yeah, I think -fa-u-t is right, otherwise you can't backtrace through
>> signal handlers.  If Darwin unwinder is lame enough that it can't grok it,
>> let it change just on Darwin and don't punish sane OSes.
> 
> Except that the signal handlers that java wants to backtrace through
> are all synchronous.  They'll never occur in the epilogue of some
> function, for instance.  Otherwise libjava would have failed to work
> for years and years.

This use of -fasynchronous-unwind-tables is in order to get backtraces
for bugs such as segfaults.  I think such bugs can trigger in prologues
and epilogues.

Andrew.