Hi there,
I am trying to reuse a piece of code that was designed as an
application. The code is covered with 'exit' calls. I would like to
reuse it as a library. For that I renamed the 'main' function into
'mymain', but I am stuck as to what I should do for the 'exit'.
AFAIK there is no portable way to catch the exit. The only thing I
can think of is atexit, but that does not work since 'exit' is still
called afterward.
What I am thinking now is that I need to replace all exit(val) with
longjmp(env, val). And make 'env' global.
Comments ?
Thanks
-Mathieu
39  2825 
On 13 Aug 2008 at 21:33, CBFalconer wrote:
mathieu wrote:
>I am trying to reuse a piece of code that was designed as an
application. The code is covered with 'exit' calls. I would like
to reuse it as a library. For that I renamed the 'main' function
into 'mymain', but I am stuck as to what I should do for the
'exit'.
Just leave it calling exit.
Brilliant.
Remind me never to use any library you write.
Oh, yes, hell would have frozen over first anyway, even without this
latest idiotic post.
CBFalconer <cb********@yah oo.comwrites:
mathieu wrote:
>I am trying to reuse a piece of code that was designed as an
application. The code is covered with 'exit' calls. I would like
to reuse it as a library. For that I renamed the 'main' function
into 'mymain', but I am stuck as to what I should do for the
'exit'.
AFAIK there is no portable way to catch the exit. The only thing
I can think of is atexit, but that does not work since 'exit' is
still called afterward.
What I am thinking now is that I need to replace all exit(val)
with longjmp(env, val). And make 'env' global.
Just leave it calling exit. The result is as follows:
7.20.4.3 The exit function
[C standard's description of the exit function snipped]
And how does this answer the OP's question?
He has a main program; a call to exit terminates the program.
He wants to turn this main program into a function within a larger
program. Wherever there's a call to exit, he wants to terminate the
function, not the entire (now larger) program.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
Keith Thompson wrote:
CBFalconer <cb********@yah oo.comwrites:
>mathieu wrote:
>>I am trying to reuse a piece of code that was designed as an
application . The code is covered with 'exit' calls. I would like
to reuse it as a library. For that I renamed the 'main' function
into 'mymain', but I am stuck as to what I should do for the
'exit'.
AFAIK there is no portable way to catch the exit. The only thing
I can think of is atexit, but that does not work since 'exit' is
still called afterward.
What I am thinking now is that I need to replace all exit(val)
with longjmp(env, val). And make 'env' global.
Just leave it calling exit. The result is as follows:
7.20.4.3 The exit function
[C standard's description of the exit function snipped]
And how does this answer the OP's question?
He has a main program; a call to exit terminates the program.
He wants to turn this main program into a function within a larger
program. Wherever there's a call to exit, he wants to terminate the
function, not the entire (now larger) program.
If that's what he wants to do that is another case. But the
previous effect was to terminate the program, whch is what exit
does.
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
CBFalconer <cb********@yah oo.comwrites:
Keith Thompson wrote:
>CBFalconer <cb********@yah oo.comwrites:
>>mathieu wrote:
I am trying to reuse a piece of code that was designed as an
applicatio n. The code is covered with 'exit' calls. I would like
to reuse it as a library. For that I renamed the 'main' function
into 'mymain', but I am stuck as to what I should do for the
'exit'.
AFAIK there is no portable way to catch the exit. The only thing
I can think of is atexit, but that does not work since 'exit' is
still called afterward.
What I am thinking now is that I need to replace all exit(val)
with longjmp(env, val). And make 'env' global.
Just leave it calling exit. The result is as follows:
7.20.4.3 The exit function
[C standard's description of the exit function snipped]
And how does this answer the OP's question?
He has a main program; a call to exit terminates the program.
He wants to turn this main program into a function within a larger
program. Wherever there's a call to exit, he wants to terminate the
function, not the entire (now larger) program.
If that's what he wants to do that is another case. But the
previous effect was to terminate the program, whch is what exit
does.
He knew that.
If he wanted the existing exit calls to terminate the program, why
would he have asked what to do about them?
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
CBFalconer said:
Keith Thompson wrote:
<snip>
>>
He has a main program; a call to exit terminates the program.
He wants to turn this main program into a function within a larger
program. Wherever there's a call to exit, he wants to terminate the
function, not the entire (now larger) program.
If that's what he wants to do that is another case.
No, it's the original question. To avoid making such mistakes in future, I
recommend that you save up your replies for an hour or so, and then:
(1) Re-read the original question, and then re-read your original reply. At
this stage, it will sometimes become clear that your reply was based on a
mis-reading of the question which your second reading makes obvious.
Solution: delete your reply without sending it.
(2) By this time, there may well be one or two other replies to the
question, by people whose opinion you respect. Read them.
If they are, in essence, the same as your own reply, delete your reply
without sending it, since it would be pointlessly duplicative (unless your
reply adds something useful that was overlooked by the others).
If they are *not* in essence the same as your reply, consider seriously the
possibility that you have mis-read the question. Read their replies, and
the original question, again, and find out why they have replied as they
did. If you genuinely interpret the question differently to them, then
edit your reply so that it says something like "I've read A's and B's
replies, and they've assumed you meant such-and-such. If so, fine. But it
seems to me that you might mean /this/ instead. If so, then my advice
is..." Then, having changed your reply, save it up for an hour or so, and
then start back at (1) again.
(3) Now send any undeleted replies.
I suggest that using this strategy could save you from a huge amount of
embarrassment.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
mathieu said:
Hi there,
I am trying to reuse a piece of code that was designed as an
application. The code is covered with 'exit' calls. I would like to
reuse it as a library. For that I renamed the 'main' function into
'mymain', but I am stuck as to what I should do for the 'exit'.
AFAIK there is no portable way to catch the exit. The only thing I
can think of is atexit, but that does not work since 'exit' is still
called afterward.
What I am thinking now is that I need to replace all exit(val) with
longjmp(env, val). And make 'env' global.
Comments ?
Eric has already given you some excellent advice, and there is no point in
duplicating it, obviously.
My comment is more in the nature of a smug, satisfied grin, I'm afraid. You
see, I don't use exit() - or at least, if I do, I consider it to be a bug
that has to be fixed. I've just searched my personal code base for exit()
calls. I found 24 altogether in 14 different C files (out of - well,
thousands), dating back in some cases to the mid-1990s. That's 24 bugs I
have to fix, which isn't too huge a job, really.
Why don't I use exit()? Well, it's a style thing, I suppose. I like to
think of big chunks being made up of little chunks, and that means that
little chunks have to behave like little chunks and not take arbitrary
decisions like "quit the program", leaving those decisions to bigger
chunks. And whilst I will grant a big chunk (think "main()") the right to
make such a decision, it is easy to revoke it (think "edit and rename one
function") if that big chunk becomes a mere part of an enormous chunk.
Unfortunately, it is not always possible to persuade other people of the
advantages of this kind of modularity. In 1994-5, I was working at V, and
the code I was working on was littered with mallocs, which were never
freed. (No, it wasn't me that did that, and I didn't have time to fix it
because I was too busy doing other stuff.) It was no big deal, said the
principal culprit, because the memory was in any case released when the
program exited. In due course, I left, and went on to work at W, X, and Y.
And then I was hired by Z, who had bought the code from X. And guess what?
They had to do precisely what you need to do - turn a program into a
function. And suddenly all these leaks mattered a great deal.
Fellow regulars in comp.lang.c often smile indulgently when I wax lyrical
about my strange stylistic habits - such as one entry point and one exit
point for each function and each loop, always initialise, always give
control back to your caller, and so on. But I have my reasons, and they
are good reasons. In this case: if the original programmer had been me,
your task would have been trivial, and we would never even have heard
about it because you wouldn't have had to ask.
Why am I telling you all this? Well, think about it the next time you write
a program. What if, one day, you need *this* program to become a function?
How hard would it be to do that? How can you make it easier?
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
On Aug 14, 9:55 am, Richard Heathfield <r...@see.sig.i nvalidwrote:
mathieu said:
Hi there,
I am trying to reuse a piece of code that was designed as an
application. The code is covered with 'exit' calls. I would like to
reuse it as a library. For that I renamed the 'main' function into
'mymain', but I am stuck as to what I should do for the 'exit'.
AFAIK there is no portable way to catch the exit. The only thing I
can think of is atexit, but that does not work since 'exit' is still
called afterward.
What I am thinking now is that I need to replace all exit(val) with
longjmp(env, val). And make 'env' global.
Comments ?
Eric has already given you some excellent advice, and there is no point in
duplicating it, obviously.
My comment is more in the nature of a smug, satisfied grin, I'm afraid. You
see, I don't use exit() - or at least, if I do, I consider it to be a bug
that has to be fixed. I've just searched my personal code base for exit()
calls. I found 24 altogether in 14 different C files (out of - well,
thousands), dating back in some cases to the mid-1990s. That's 24 bugs I
have to fix, which isn't too huge a job, really.
Why don't I use exit()? Well, it's a style thing, I suppose. I like to
think of big chunks being made up of little chunks, and that means that
little chunks have to behave like little chunks and not take arbitrary
decisions like "quit the program", leaving those decisions to bigger
chunks. And whilst I will grant a big chunk (think "main()") the right to
make such a decision, it is easy to revoke it (think "edit and rename one
function") if that big chunk becomes a mere part of an enormous chunk.
Unfortunately, it is not always possible to persuade other people of the
advantages of this kind of modularity. In 1994-5, I was working at V, and
the code I was working on was littered with mallocs, which were never
freed. (No, it wasn't me that did that, and I didn't have time to fix it
because I was too busy doing other stuff.) It was no big deal, said the
principal culprit, because the memory was in any case released when the
program exited. In due course, I left, and went on to work at W, X, and Y.
And then I was hired by Z, who had bought the code from X. And guess what?
They had to do precisely what you need to do - turn a program into a
function. And suddenly all these leaks mattered a great deal.
Fellow regulars in comp.lang.c often smile indulgently when I wax lyrical
about my strange stylistic habits - such as one entry point and one exit
point for each function and each loop, always initialise, always give
control back to your caller, and so on. But I have my reasons, and they
are good reasons. In this case: if the original programmer had been me,
your task would have been trivial, and we would never even have heard
about it because you wouldn't have had to ask.
Why am I telling you all this? Well, think about it the next time you write
a program. What if, one day, you need *this* program to become a function?
How hard would it be to do that? How can you make it easier?
So to paraphrase you, I should have said:
....
While working at X, I am trying to reuse a piece of code that was
designed by
Y as an application, in mid 1990. The code is covered with 'exit'
calls...
....
:)
Anyway to put names, I am talking about the PVRG JPEG library (google
it if needed). And it is producing a bizarre JPEG compression for 16
bits lossless that I simply *cannot* reproduce using IJG (google). So
the only way I can support those damned lossless JPEG is to link to
PVRG. I am not very keen on 'system' call, as I do not know how
portable they are. So yes I am stuck on reusing this piece of code,
and my goal is to spent little time as possible.
-Mathieu
In article <ln************ @nuthaus.mib.or g>,
Keith Thompson <ks***@mib.orgw rote in a splendid little chick fight
leading up to:
....
>He knew that.
If he wanted the existing exit calls to terminate the program, why
would he have asked what to do about them?
Looks like Keith is getting caught up in his own little web.
Are you guys beginning to see how pointless these little pedantic
quibbles are? How silly it looks when all you are doing is redefining
OP's questions to suit your own petty little agendas?
CBFalconer wrote:
Keith Thompson wrote:
>CBFalconer <cb********@yah oo.comwrites:
>>mathieu wrote:
I am trying to reuse a piece of code that was designed as an
applicatio n. The code is covered with 'exit' calls. I would like
to reuse it as a library. For that I renamed the 'main' function
into 'mymain', but I am stuck as to what I should do for the
'exit'.
AFAIK there is no portable way to catch the exit. The only thing
I can think of is atexit, but that does not work since 'exit' is
still called afterward.
What I am thinking now is that I need to replace all exit(val)
with longjmp(env, val). And make 'env' global.
Just leave it calling exit. The result is as follows:
....
>He wants to turn this main program into a function within a larger
program. Wherever there's a call to exit, he wants to terminate the
function, not the entire (now larger) program.
If that's what he wants to do that is another case.
No, that's the original case, not another one.
... But the
previous effect was to terminate the program, whch is what exit
does.
And he made it abundantly clear, I thought, that the point of his
question was about not wanting to terminate the program. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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