• Davidl 126.com (48/48) Mar 07 2007 i've seen reactos hacker suffer from PSEH thingie.
• Derek Parnell (28/49) Mar 07 2007 What is wrong with ...
• Sean Kelly (11/61) Mar 08 2007 This could probably be sorted out with some clever programming, but I'm

Davidl 126.com writes:

i've seen reactos hacker suffer from PSEH thingie.
and they use a macro to implement PSEH try block.
the PSEH try block would looks like
_PSEH_TRY
{
....
}
_PSEH_EXCEPT
{
...
}
_PSEH_END

this is a good idea since all try block code implemented
in C. and it's more portable than
try
{
}
except
{
}

but it's very difficult to ensure it's correct. and also the
binary generated is dummy and low efficient, cause the idea
of it is implemented roughly as following

for(;;)
{
if not firsttimevisit
{
   ... try  code
   break;
}
else
{
    if (setjmp(label1))
    label1:
    {
       ... finally code
    }
    else
    {
       continue;
    }
}
}

any idea of meta-programming of implementing this try block
stuff? or need some compiler support?

and binding try block binary with compiler is really ain't a
good idea, compiler needs to support linux version, windows
version.

Derek Parnell <derek nomail.afraid.org> writes:

On Thu, 08 Mar 2007 15:17:45 +0800, Davidl 126.com wrote:

 i've seen reactos hacker suffer from PSEH thingie.
 and they use a macro to implement PSEH try block.
 the PSEH try block would looks like

Huh?  Can somebody translate that into English for me?

 _PSEH_TRY
 {
 ....
 }
 _PSEH_EXCEPT
 {
 ...
 }
 _PSEH_END
 
 this is a good idea since all try block code implemented
 in C. and it's more portable than
 try
 {
 }
 except
 {
 }

What is wrong with ... 

  try
  {
    ... some code ...
  }
  catch
  {
    ... oops! something went wrong, so handle it.  ...
  }
  finally
  {
    ... All is well, so deal with that ...
  }

How does this not suit your needs?

Or is the 'scope' syntax better for you?

 {
   ... some code ...
   scope(failure) {... oops! something went wrong, so handle it.  ...}
   scope(success) {... All is well, so deal with that ...}
 }

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Justice for David Hicks!"
8/03/2007 6:22:15 PM

Sean Kelly <sean f4.ca> writes:

Davidl 126.com wrote:
 
 i've seen reactos hacker suffer from PSEH thingie.
 and they use a macro to implement PSEH try block.
 the PSEH try block would looks like
 _PSEH_TRY
 {
 .....
 }
 _PSEH_EXCEPT
 {
 ....
 }
 _PSEH_END
 
 this is a good idea since all try block code implemented
 in C. and it's more portable than
 try
 {
 }
 except
 {
 }
 
 but it's very difficult to ensure it's correct. and also the
 binary generated is dummy and low efficient, cause the idea
 of it is implemented roughly as following
 
 for(;;)
 {
 if not firsttimevisit
 {
   ... try  code
   break;
 }
 else
 {
    if (setjmp(label1))
    label1:
    {
       ... finally code
    }
    else
    {
       continue;
    }
 }
 }
 
 any idea of meta-programming of implementing this try block
 stuff? or need some compiler support?

This could probably be sorted out with some clever programming, but I'm 
not sure it's a good idea.  Depending on the platform, longjmp may or 
may not execute dtors and such as it moves its way up the stack.  If it 
doesn't, the app could leak resources.  If it does, you're doing the 
same thing as normal exception handling and gain nothing.  If 
performance is really a concern, it might be worth investigating the 
exception handing mechanism itself and see if that can be optimized. 
Win32 uses SEH, and I think Win64 uses some new method.  And exception 
handling in Unix is largely hand-coded into phobos (see internal/deh.d).


Sean