[fpc-devel] Exceptions on wiki

[J. Gareth Moreton]

 The information in the Wiki about how exception frames are set up is
pretty nice. I didn't know that 'raise' creates an exception frame for the
procedure it appears in, but explains why it's often shipped off to another
local procedure. Very useful information!
 True though, it's hard to generalise the performance impact of exception
handlers and try...finally blocks, although I think the simple rule of
thumb is that there is a performance hit no matter what you try.

 Gareth aka. Kit

 On Thu 02/08/18 06:54 , Sven Barth via fpc-devel
fpc-devel at lists.freepascal.org sent:
 Kirinn  schrieb am Mi., 1. Aug. 2018, 23:30:
 Hi all,

 Inspired by Gareth aka. Kit's infectious enthusiasm, and the recent long 
 discussion on exceptions on this list, I wrote up an article on 
 Exceptions on the FPC wiki. (Strangely enough we didn't have one before.)

 http://wiki.freepascal.org/Exceptions [2]

 I hope it'll be useful, and not entirely inaccurate! Particularly the 
 part about performance. If a programmer knows exactly what each 
 exception statement inserts in the code, that should help in deciding 
 when to worry about the performance, and when to embrace the convenience.

 Please note that you can't generalize the performance impact as it depends
on the used exception handling mechanism. By default FPC uses
setjmp/longjmp which exhibit the behavior you described. On Win64 however
SEH is used which - in that platform - relies on metadata inside the binary
to mark the areas for a protected block (no matter whether it's for
"except" or "finally"). On Win32 with SEH enabled (which isn't the default
currently) it is again different. And should we decide to support DWARF
exception frames that would again be different.  
 Regards, Sven   _______________________________________________
 fpc-devel maillist - fpc-devel at lists.freepascal.org [3]
 http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
[4]">http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel

 

Links:
------
[1] mailto:kirinn at mooncore.eu
[2] http://wiki.freepascal.org/Exceptions
[3] mailto:fpc-devel at lists.freepascal.org
[4] http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
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