[fpc-pascal] How do FreePascal implement hardware exceptions handling?

[Sven Barth]

On 15.12.2012 18:40, Andrzej Borucki wrote:
> I analyze FreePascal exceptions handling. Instead use of
> try-excpt-finally statement I rather use fpc_LongJmp,fpc_PushExceptAddr
> etc. It works fine for software exceptions (fpc_RaiseException) but not
> handle hardware exceptions.

FPC relies on the hardware exception support provided by the operating 
system. For Windows this is accomplished by using 
SetUnhandledExceptionFilter (or using SEH on Windows 64 if the compiler 
is compiled with the correct define) while on Unix this means that 
signals like SIGSEGV or SIGFPE are hooked.

It is not recommended to use "fpc_LongJmp", "fpc_PushExceptAddr" etc. 
manually as FPC's code generation could interfere with your intentions 
here (note: the correct way of using longjmp would be by using the 
function LongJmp instead of fpc_LongJmp (and likewise SetJmp instead of 
fpc_SetJmp).

So: why are you doing this?

> I use install_exception_handlers at start
> program. This call
> SetUnhandledExceptionFilter(@syswin32_i386_exception_handler) but is
> problem:
> in syswin32_i386_exception_handler is comparing "if
> excep^.ContextRecord^.SegSs = _SS then" - _SS is correct stack segment
> but excep^.ContextRecord^.SegSs - no, it is a different value, why?
> I can attach my files

Why are you doing this? install_exception_handlers is called during 
process entry of Win32/Win64 programs already, so calling this twice can 
be considered a bad(TM) idea.

Regards,
Sven