Hints on how to migrate from C++ to C

[Sune]

Hi!

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

To get going I would need a cross reference on how to replace
useful C++ features with their C equivalents. Since I'm quite C++
literate (and also lazy) this shortcut is needed to ever make it
happen, I think. A truly good tricks'n'hints doc would also do it
as long as what's suggested in it is somewhat accepted in the C
industry.

Something like:

C++ construct C counterpart
--------------- ----------------
Exceptions ...
Resource ownership ...

If too many 'useful' C++ constructs cannot be represented in C this
will also stop my migration.

I've got a decent knowledge of what is doable in C, but I haven't LIVED
with C as I have with C++, so my hope goes out to you guys!

Thanks in advance
/Sune

[Free Bird]

Sune wrote:

C++ construct C counterpart
--------------- ----------------
Exceptions ... Three possibilities:
1) Returning an error code
2) Setting a global error variable
3) Raising a signal
Resource ownership ...

AFAICS, there are two possibilities:
1) The static keyword
2) Your own self-restraint

I hope that helps. Don't expect a seamless transition, though. If all C++
constructs could easily be translated to C without any loss of meaning than
we wouldn't need C++.

[Rouben Rostamian]

In article <11**********************@g43g2000cwa.googlegroups .com>,
Sune <su**********@hotmail.com> wrote:

Hi!

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

To get going I would need a cross reference on how to replace
useful C++ features with their C equivalents. Since I'm quite C++
literate (and also lazy) this shortcut is needed to ever make it
happen, I think. A truly good tricks'n'hints doc would also do it
as long as what's suggested in it is somewhat accepted in the C
industry.

Something like:

C++ construct C counterpart
--------------- ----------------
Exceptions ...
Resource ownership ...

If too many 'useful' C++ constructs cannot be represented in C this
will also stop my migration.

The old saying goes: when in Rome, do as the Romans do. It is
counterproductive to move to a new language and try to preserve
your old idioms in the new language. A programming language
comes with its own philosophy and world-view. It's pointless
to coerce it to fit another language's world-view. If you try,
then at best you will be writing programs in one language that
speak with another language's accent.

My point is, don't look for a table of matching idioms in C
and C++. You may construct such a table, but it is the wrong
approach. Instead, immerse yourself in C and express your ideas
in accepted C paradigms. Don't carry over C++ paradigms to C.

That said, if you want to push C to talk with a slight C++ accent,
have look at "C Interfaces and Implementations" by David Hanson.

--
Rouben Rostamian

[Sune]

Rouben Rostamian skrev:

In article <11**********************@g43g2000cwa.googlegroups .com>,
Sune <su**********@hotmail.com> wrote:

Hi!

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

To get going I would need a cross reference on how to replace
useful C++ features with their C equivalents. Since I'm quite C++
literate (and also lazy) this shortcut is needed to ever make it
happen, I think. A truly good tricks'n'hints doc would also do it
as long as what's suggested in it is somewhat accepted in the C
industry.

Something like:

C++ construct C counterpart
--------------- ----------------
Exceptions ...
Resource ownership ...

If too many 'useful' C++ constructs cannot be represented in C this
will also stop my migration.

The old saying goes: when in Rome, do as the Romans do. It is
counterproductive to move to a new language and try to preserve
your old idioms in the new language. A programming language
comes with its own philosophy and world-view. It's pointless
to coerce it to fit another language's world-view. If you try,
then at best you will be writing programs in one language that
speak with another language's accent.

My point is, don't look for a table of matching idioms in C
and C++. You may construct such a table, but it is the wrong
approach. Instead, immerse yourself in C and express your ideas
in accepted C paradigms. Don't carry over C++ paradigms to C.

That said, if you want to push C to talk with a slight C++ accent,
have look at "C Interfaces and Implementations" by David Hanson.

--
Rouben Rostamian

Thanks for your viewpoint, but why would it be counter productive to
use the best of two worlds?

It's like saying:
- Either drink milk or coffe, DO NOT put milk in your coffe, that's
counter productive!

Just trying to keep an open mind...

[Alan Balmer]

On 27 Jul 2005 06:47:12 -0700, "Sune" <su**********@hotmail.com>
wrote:

It's like saying:
- Either drink milk or coffe, DO NOT put milk in your coffe, that's
counter productive!

If you have two consumers, one who can't drink milk and the other who
can't drink coffee, you've ruined it for both of them.

--
Al Balmer
Balmer Consulting
re************************@att.net

[Sune]

Why does a mix of milk and coffe make consumers allergic???

Cows can't jump - Confucius

[Martin Ambuhl]

Sune wrote:

Cows can't jump - Confucius

I have grepped my copy of _Lunyu_ and cannot find any such statement.
Do you have a citation for that?

[John Bode]

Sune wrote:

Hi!
[snip]
C++ construct C counterpart
--------------- ----------------
Exceptions ...
Resource ownership ...

Off the top of my head:

C++ C
---------- ------------
classes no equivalent
inheritance no equivalent
exceptions signal/raise,
setjmp/longjmp
iostreams stdio (*scanf(),
*printf(), read(),
write(), fgetc(),
fputc(), etc.)
polymorphism no equivalent
(variadic functions
DO NOT count)
templates no equivalent
operator no equivalent
overloading

[Sune]

Hi!

I totally appreciate your effort, thanks.

2 clarifications:
- I guess with your exception approach there will be some
additional work compared with C++, possible recursive call
unwinding etc?
- What can I implement in terms of resource ownership? Is
there a way, I'm totally C from now on.

BRs
/Olle

[tedu]

John Bode wrote:

C++ C
---------- ------------
classes no equivalent
inheritance no equivalent

Structs with function pointers come close.

[Malcolm]

"Sune" <su**********@hotmail.com> wrote

[ C++ like C ]
Thanks for your viewpoint, but why would it be counter productive to
use the best of two worlds?

It's like saying:
- Either drink milk or coffe, DO NOT put milk in your coffe, that's
counter productive!

Sometimes you can take a good idea from another programming language, and
use it in your own. Generally, however, the good idea requires some support
that the other language doesn't have.
For instance C++ exceptions are arguably such a good idea, and can be faked
up in C somehow. However C offers no mechanism for automatically freeing
objects called by malloc(), so you cannot unwind the stack. This makes any
attempt to implement exceptions in C very difficult and error prone. So in
fact you are better off using error return codes to indicate error
conditions in C code.

[Keith Thompson]

"Sune" <su**********@hotmail.com> writes:

I totally appreciate your effort, thanks.

2 clarifications:
- I guess with your exception approach there will be some
additional work compared with C++, possible recursive call
unwinding etc?
- What can I implement in terms of resource ownership? Is
there a way, I'm totally C from now on.

Can you clarify what you mean by "resource ownership"?

If you need some of the features that C++ provides and C doesn't, but
you dislike some aspects of C++, you can always just program in a
subset of C++. Use the features you like, and ignore the ones you
don't. (Though ignoring features isn't necessarily easy.)

C90 is very nearly a subset of C++. If you write code that's
basically C-like except that it uses C++ exceptions, for example, you
can compile it with a C++ compiler.

If you take this approach, you'll need to discuss it in comp.lang.c++.

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Old Wolf]

Sune wrote:

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

To get going I would need a cross reference on how to replace
useful C++ features with their C equivalents. Since I'm quite C++
literate (and also lazy) this shortcut is needed to ever make it
happen, I think. A truly good tricks'n'hints doc would also do it
as long as what's suggested in it is somewhat accepted in the C
industry.

Something like:

C++ construct C counterpart
--------------- ----------------
Exceptions ...
Return a value from the function, indicating success or failure.
The calling function tests this value and takes appropriate
action.
Resource ownership ...
Free the resource when you are finished with it.

It may be beneficial to register a function with atexit()
if your operating system isn't going to automatically clean
up resources when the program exits.
If too many 'useful' C++ constructs cannot be represented in C this
will also stop my migration.

Why are you migrating anyway. You suggest that you don't like
some aspects of C++ -- if so, then simply stop using those
aspects, and use its C-like aspects instead. That's got to
be simpler than a total rewrite.

[Sune]

Hi all,

your remarks and hints are all valid. They can be summed up as:

1) If you write code that's basically C-like except that it uses
C++ exceptions, for example, you can compile it with a C++
compiler.

2) Tweaks as those suggested will be error prone, don't use them.

1. IMHO C will stand the test of time better than C++ if the
current trends in C++ continues, mainly: STL suckage and
syntactic sugar rushes. This is the main reason I asked these
seemingly awkward questions.

2. I hoped for tweaks, even ugly ones, to be able to use a C
in a C++ like way in some situations. However this seems,
according to you and my newly adopted opinion, not to be
the case. (A few C++ constructs and idioms are very
powerful; this is why I hoped for 'clones' in C).

Conclusion
------------------------
I will implement my application in a procedural C-like manner,
using C++ (hopefully being able to restrain C++ a bit and thus
save it from itself).

Thanks for your time and input!

BRs
/Sune

[Richard Heathfield]

Sune wrote:

Hi!

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

To get going I would need a cross reference on how to replace
useful C++ features with their C equivalents.
No problem.
Since I'm quite C++
literate (and also lazy) this shortcut is needed to ever make it
happen, I think.
Here's the whole thing: use a C compiler instead of a C++ compiler, and fix
all the resulting error messages. That will probably sort out 99% of your
problems.
Something like:

C++ construct C counterpart
--------------- ----------------
Exceptions ...
return errorcode;
Resource ownership ...
/* this bit's MINE! */

If too many 'useful' C++ constructs cannot be represented in C this
will also stop my migration.
If C++ constructs were all that useful, you wouldn't be moaning about them.

I've got a decent knowledge of what is doable in C, but I haven't LIVED
with C as I have with C++, so my hope goes out to you guys!

The door is open. Just bring your things in and find a desk. The water
cooler is over there in the corner.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
mail: rjh at above domain

[Richard Bos]

Martin Ambuhl <ma*****@earthlink.net> wrote:

Sune wrote:

Cows can't jump - Confucius

I have grepped my copy of _Lunyu_ and cannot find any such statement.
Do you have a citation for that?

Confucius say "Conficius say more in English than in Chinese".

Richard

[Alan Balmer]

On Thu, 28 Jul 2005 06:37:34 GMT, rl*@hoekstra-uitgeverij.nl (Richard
Bos) wrote:

Martin Ambuhl <ma*****@earthlink.net> wrote:

Sune wrote:

> Cows can't jump - Confucius

I have grepped my copy of _Lunyu_ and cannot find any such statement.
Do you have a citation for that?

Confucius say "Conficius say more in English than in Chinese".

Richard

He was ahead of his time.

--
Al Balmer
Balmer Consulting
re************************@att.net

[John Bode]

tedu wrote:

John Bode wrote:

C++ C
---------- ------------
classes no equivalent
inheritance no equivalent

Structs with function pointers come close.

For sufficiently distant values of "close".

[Roger Leigh]

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Hash: SHA1

"Sune" <su**********@hotmail.com> writes:

C++ construct C counterpart
--------------- ----------------
Exceptions ...

There are mechanisms for propagating errors back up the call stack in
C. Here's one of them:

http://developer.gnome.org/doc/API/2...Reporting.html

And here's an example of its use:

http://cvs.alioth.debian.org/cgi-bin...t=buildd-tools
http://cvs.alioth.debian.org/cgi-bin...t=buildd-tools

In the header, all the ERROR enums and macros are the error codes for
the SBUILD_AUTH_ERROR error domain (equivalent to a derived exception
class, but perhaps a little more useful in practice). In the source,
sbuild_auth_run() shows how errors may be propagated up the call
stack; all the preceding functions may "throw" (propagate) an error.

This method is rather more "manual" than C++ exceptions, but in
practice is mostly equivalent. It has the advantage that you can't
have an unhandled exception abort the application unexpectedly because
all the error propagation is explicit, and because it's passed on the
stack, it's part of the function signature.

Here's where that object's exceptions are caught at the top-level:
http://cvs.alioth.debian.org/cgi-bin...t=buildd-tools
(10 lines from the bottom).
Regards,
Roger

- --
Roger Leigh
Printing on GNU/Linux? http://gimp-print.sourceforge.net/
Debian GNU/Linux http://www.debian.org/
GPG Public Key: 0x25BFB848. Please sign and encrypt your mail.
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[Rob Thorpe]

Sune wrote:

Hi all,

your remarks and hints are all valid. They can be summed up as:

1) If you write code that's basically C-like except that it uses
C++ exceptions, for example, you can compile it with a C++
compiler.

2) Tweaks as those suggested will be error prone, don't use them.

1. IMHO C will stand the test of time better than C++ if the
current trends in C++ continues, mainly: STL suckage and
syntactic sugar rushes. This is the main reason I asked these
seemingly awkward questions.

2. I hoped for tweaks, even ugly ones, to be able to use a C
in a C++ like way in some situations. However this seems,
according to you and my newly adopted opinion, not to be
the case. (A few C++ constructs and idioms are very
powerful; this is why I hoped for 'clones' in C).

Conclusion
------------------------
I will implement my application in a procedural C-like manner,
using C++ (hopefully being able to restrain C++ a bit and thus
save it from itself).

Thanks for your time and input!

One more thing:

Many people, myself included, think that exceptions are overused.
Their purpose should be to treat truely exceptional situations..

A good program is one that never uses exceptions. They should be a
port of final call if an error cannot be propagated through the program
in a more structured way.

[Simon Biber]

Richard Bos wrote:

Martin Ambuhl <ma*****@earthlink.net> wrote:

Sune wrote:

Cows can't jump - Confucius

I have grepped my copy of _Lunyu_ and cannot find any such
statement. Do you have a citation for that?

Confucius say "Conficius say more in English than in Chinese".

å*�曰：“å*�曰英文多于ä¸*æ–‡â€�。

--
Simon.

[Emmanuel Delahaye]

Sune wrote on 27/07/05 :

It's like saying:
- Either drink milk or coffe, DO NOT put milk in your coffe, that's
counter productive!

Just trying to keep an open mind...

Coffee and milk are well known poisons.

http://www.justeatanapple.com/coffee.html
http://www.notmilk.com/
http://www.milksucks.com/index2.html

Coffee + milk.. I can't imagine...

http://www.meridianinstitute.com/ech...s/1coffee.html

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"

[Emmanuel Delahaye]

Simon Biber wrote on 30/07/05 :

Confucius say "Conficius say more in English than in Chinese".

åí�æ›°ïüšâ€œåí�曰英文åäšäºŽä¸*æ–‡â€�ãÀ‚

Cute !

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"

[Emmanuel Delahaye]

Sune wrote on 27/07/05 :

I've been designing telecom applications in C++ for 8 years now
and I'm being fed up with parts of OO and C++.

http://ldeniau.home.cern.ch/ldeniau/html/oopc/oopc.html
http://ldeniau.home.cern.ch/ldeniau/...exception.html

Have fun !

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"C is a sharp tool"

[Emmanuel Delahaye]

(supersedes <mn***********************@YOURBRAnoos.fr>)

Simon Biber wrote on 30/07/05 :

Confucius say "Conficius say more in English than in Chinese".

åí�æ›°ïüšâ€œåí�曰英文åäšäºŽä¸*æ–‡â€�ãÀ‚

"Sub- says: 'the child says the English are many to Chinese'"

Cute!

I think the the chinese people will have fun with Google translation
like we have!

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"Mal nommer les choses c'est ajouter du malheur au
monde." -- Albert Camus.

[Chris Croughton]

On Sat, 30 Jul 2005 21:34:51 +0200, Emmanuel Delahaye
<em***@YOURBRAnoos.fr> wrote:

Sune wrote on 27/07/05 :

It's like saying:
- Either drink milk or coffe, DO NOT put milk in your coffe, that's
counter productive!

Just trying to keep an open mind...

Coffee and milk are well known poisons.

http://www.justeatanapple.com/coffee.html
http://www.notmilk.com/
http://www.milksucks.com/index2.html

Coffee + milk.. I can't imagine...

http://www.meridianinstitute.com/ech...s/1coffee.html

It's worse than that, coffee is made with DiHydrogen Monoxide (also
known as Hydrogen Hydroxide) which is a well-known factor in thousands
of deaths every year (as well as being a bad influence on the greenhouse
effect and very corrosive).

Milk also contains large quantities of this substance, which may account
for its toxicity.

http://www.dhmo.org/facts.html

Chris C

[Emmanuel Delahaye]

Chris Croughton wrote on 31/07/05 :

It's worse than that, coffee is made with DiHydrogen Monoxide (also

sounds like water (H²O) to me...
--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"C is a sharp tool"

[Alexei A. Frounze]

"Emmanuel Delahaye" <em***@YOURBRAnoos.fr> wrote in message
news:mn***********************@YOURBRAnoos.fr...

Chris Croughton wrote on 31/07/05 :

It's worse than that, coffee is made with DiHydrogen Monoxide (also

sounds like water (H²O) to me...

That's what it is :) You can write it as H<subscript>2</subscript>O or as
HOH, it still is the same thing. It's the most damned substance, because if
there's not enough of it (imagine a desert or an empty pool you're falling
in:) you have a problem and if there's too much of it (imagine a tsunami)
you have another problem, and yes, over the time it turns your car into a
selfmoving garbage :)

Alex

[CBFalconer]

Emmanuel Delahaye wrote:

Chris Croughton wrote on 31/07/05 :

It's worse than that, coffee is made with DiHydrogen Monoxide

sounds like xxxxx (XnX) to me...

Hush. You are spoiling the effect. We could have a long
discussion of the relative performance of hardware exposed to
monoxides vs dioxides, for example. It could get crossposted to
some chemistry group, thus giving it a long life.

--
"If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

[Chris Croughton]

On Sun, 31 Jul 2005 16:08:32 +0400, Alexei A. Frounze
<al*****@chat.ru> wrote:

"Emmanuel Delahaye" <em***@YOURBRAnoos.fr> wrote in message
news:mn***********************@YOURBRAnoos.fr...

Chris Croughton wrote on 31/07/05 :

> It's worse than that, coffee is made with DiHydrogen Monoxide (also
sounds like water (H²O) to me...

Well, you can use the slang name, yes <g>.
That's what it is :) You can write it as H<subscript>2</subscript>O or as
HOH, it still is the same thing. It's the most damned substance, because if
there's not enough of it (imagine a desert or an empty pool you're falling
in:) you have a problem and if there's too much of it (imagine a tsunami)
you have another problem, and yes, over the time it turns your car into a
selfmoving garbage :)

In vapour form it is also one of the worst greenhouse gasses, it traps the
heat better than most of the others. It also breaks down ozone (there was
someing in news reports about that the other day). And it is, of course,
the major component of acid rain <g>. (In fact all of the examples on
www.dhmo.org are correct, they are just worded in the same way that typical
food 'scare' stories are done.)

And don't think what fish do in it...

Chris C

[Simon Biber]

Emmanuel Delahaye wrote:

"Sub- says: 'the child says the English are many to Chinese'"

Cute!

I think the the chinese people will have fun with Google translation
like we have!

Google's translator (Systran) does not recognise the phrase "å*�æ›°"
(Pinyin zi3 yue1, Confucius said). In this case the å*� is short for å*”å*�
(kong3 zi3, Confucius). In this usage the meaning of å*� is a polite way
to refer to somebody respected. The character å*� also has the meaning
"child" or "son".

Simon.

[Randy Howard]

CBFalconer wrote
(in article <42***************@yahoo.com>):

Emmanuel Delahaye wrote:

Chris Croughton wrote on 31/07/05 :

It's worse than that, coffee is made with DiHydrogen Monoxide

sounds like xxxxx (XnX) to me...

Hush. You are spoiling the effect.

Anyone see the Penn and Teller Bull$%^& episode on showtime a
while back where they went to a "earth first" style eco-whacko
rally and got everybody they could find, including a
spokesperson for one of the groups to sign a petition to "ban
dihyrdogen monoxide"? It was a riot.

--
Randy Howard (2reply remove FOOBAR)

[CBFalconer]

Randy Howard wrote:

CBFalconer wrote

Emmanuel Delahaye wrote:

Chris Croughton wrote on 31/07/05 :

It's worse than that, coffee is made with DiHydrogen Monoxide

sounds like xxxxx (XnX) to me...

Hush. You are spoiling the effect.

Anyone see the Penn and Teller Bull$%^& episode on showtime a
while back where they went to a "earth first" style eco-whacko
rally and got everybody they could find, including a
spokesperson for one of the groups to sign a petition to "ban
dihyrdogen monoxide"? It was a riot.

No, but I can imagine. Unfortunately such spoofs need to be
balanced by others deriding the action of the "destroy and grow
rich" style rabid rightists, such as attempts to build more fission
reactors in preference to economies such as a higher CAFE.

--
Chuck F (cb********@yahoo.com) (cb********@worldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net> USE worldnet address!