On Mon, Jan 10, 2011 at 11:31 PM, Andres Valloud <avalloud@smalltalk.comcastbiz.net> wrote:

Indeed, quite right. �I happened to add a flag to turn off the heartbeat
so I could debug the crash Matthew was seeing in starting up
Squeak4.2-10856-beta.image (since single-stepping through machine code
always gets interrupted by the heartbeat, it being an interval timer)
and lo and behold the bug went away. �This is very worrying because it
appears to imply that there's a serious bug in the linux kernel/gcc
since delivering a software interrupt shouldn't corrupt registers, but
it clearly does. �I'll try and pass it by someone who's an expert in
this area.

Or the signal handler functions do not comply with the relevant specifications, e.g.: signal handlers that do not preserve the value of errno, signal handlers that use a function not in the list of approved safe functions you can call from a signal handler as per the Single Unix Specification, etc...

Good point. �The signal handler essentially calls gettimeofday (not on the approved list but time is) and sets a couple of variables (current 64-bit microsecond time, stackLimit). �But it does not preserve errno. �I don't want to avoid calling gettimeofday and can see no harm in it; it's equivalent internally to time providing it doesn't use its TIMEZONE arg (which it doesn't). �But the signal handler /doesn't/ preserve errno and doing so is a very good idea and easy to do. �Thanks.

Andres.