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digitalmars.D.learn - setjmp / longjmp

reply "Cassio Butrico" <cassio_butrico ig.com.br> writes:
Hello everyone , first congratulations for the wonderful forum , 
I wish someone could help me , I am writing a small basic 
interpreter in D and I am with some difficulties.

estoutentando manupular the setjmp / longjmp buffers , but the 
error , I use windows 7 and the dmd 2067 , will be whose 
manipulate the buffers save and return ? Excuse my english sucks.
Apr 25 2015
parent reply ketmar <ketmar ketmar.no-ip.org> writes:
On Sat, 25 Apr 2015 23:25:13 +0000, Cassio Butrico wrote:


 Hello everyone , first congratulations for the wonderful forum , I wish
 someone could help me , I am writing a small basic interpreter in D and
 I am with some difficulties.
=20
 estoutentando manupular the setjmp / longjmp buffers , but the error , I
 use windows 7 and the dmd 2067 , will be whose manipulate the buffers
 save and return ? Excuse my english sucks.


you shouldn't use setjmp/longjmp in D. use exceptions instead. something=20
like this:

instead of setjmp:
try {
  doit
} catch (MyException e) {
  process e
}

and instead of longjmp:
throw new MyException();
=
Apr 25 2015
next sibling parent "Cassio Butrico" <cassio_butrico ig.com.br> writes:
On Sunday, 26 April 2015 at 05:56:46 UTC, ketmar wrote:

 On Sat, 25 Apr 2015 23:25:13 +0000, Cassio Butrico wrote:


 Hello everyone , first congratulations for the wonderful forum 
 , I wish
 someone could help me , I am writing a small basic interpreter 
 in D and
 I am with some difficulties.
 
 estoutentando manupular the setjmp / longjmp buffers , but the 
 error , I
 use windows 7 and the dmd 2067 , will be whose manipulate the 
 buffers
 save and return ? Excuse my english sucks.


 you shouldn't use setjmp/longjmp in D. use exceptions instead. 
 something
 like this:

 instead of setjmp:
 try {
   doit
 } catch (MyException e) {
   process e
 }

 and instead of longjmp:
 throw new MyException();



Thank you for answering me ketmar
I will try this
Apr 26 2015
prev sibling parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
On 26/04/2015 06:56, ketmar wrote:
<snip>

 you shouldn't use setjmp/longjmp in D. use exceptions instead. something
 like this:


<snip>

True in the general case.  Still, there must be some reason that trying it in D
causes an 
AV (even if I disable the GC).  I remain curious about what that reason is.

Some time ago, just for fun, I wrote an Unlambda to D compiler.  Except that I
couldn't 
get the c builtin to work properly.  Exceptions cover typical uses cases, but a
subtlety 
of it is that (roughly speaking) the continuation it emits can escape from the
function it 
is passed into, and then when the continuation is later invoked it should
return the 
program to the point at which c was invoked.  Essentially, it can wind the
stack as well 
as unwinding it.  I envisaged that, maybe with the aid of setjmp and some trick
to get GC 
to work with it, it could be made to work.

Stewart.

-- 
My email address is valid but not my primary mailbox and not checked regularly.
 Please 
keep replies on the 'group where everybody may benefit.
Apr 26 2015
next sibling parent "Cassio Butrico" <cassio_butrico ig.com.br> writes:
I'm just building a small interpreter with a script and wanted to 
handle errors diverting the flow and returning .
I am grateful for having responded my question , thank you.
Apr 26 2015
prev sibling parent reply ketmar <ketmar ketmar.no-ip.org> writes:
On Sun, 26 Apr 2015 21:45:41 +0100, Stewart Gordon wrote:


 On 26/04/2015 06:56, ketmar wrote:
 <snip>

 you shouldn't use setjmp/longjmp in D. use exceptions instead.
 something like this:


 <snip>
=20
 True in the general case.  Still, there must be some reason that trying
 it in D causes an AV (even if I disable the GC).  I remain curious about
 what that reason is.


i believe this has something to do with exception frames. but it needs=20
further investigation.=
Apr 27 2015
parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
On 27/04/2015 10:41, ketmar wrote:
<snip>

 i believe this has something to do with exception frames. but it needs
 further investigation.


What is an exception frame, exactly?

Moreover, are these frames applicable even in sections of code where no
throwing or 
catching of exceptions takes place?

Stewart.

-- 
My email address is valid but not my primary mailbox and not checked regularly.
 Please 
keep replies on the 'group where everybody may benefit.
Jun 09 2015
parent ketmar <ketmar ketmar.no-ip.org> writes:
On Tue, 09 Jun 2015 11:57:03 +0100, Stewart Gordon wrote:


 On 27/04/2015 10:41, ketmar wrote:
 <snip>

 i believe this has something to do with exception frames. but it needs
 further investigation.


=20
 What is an exception frame, exactly?


to correctly do unwinding and other interesting things exception handler=20
should do, compiler must establish special hidden structures in the form=20
of single-linked list, so runtime can traverse it backwards if it needs=20
to unwind the stack (i.e. calling destructors for structs, for example).


 Moreover, are these frames applicable even in sections of code where no
 throwing or catching of exceptions takes place?


exception can be thrown by function that is called from your code.=20
compiler needs to setup structures to correctly "unwind" the stack in=20
this case. if nothing will throw, that setup cost as almost zero and can=20
be ignored. but playing games with stack can lead to corruption of such=20
structures (runtime doesn't know that stack was changed, and it can't=20
update it's internal data structures accordingly). this may be harmless,=20
or may lead to crash, or may lead to memory corruption without immediate=20
crashing, or... effects are unpredictable.

tldr; don't use setjmp/longjmp in the language with exceptions, unless=20
you can describe it's runtime internals and exception handling down to=20
assembler code when you're awaken at night completely drunk. ;-)=
Jun 09 2015