Is it a good thing that program mix C and C++?
Mar 28 '07
45  2079 
On Mar 28, 1:39 pm, "Sheth Raxit" <raxitsheth2... @yahoo.co.inwro te:
On Mar 28, 11:33 am, CBFalconer <cbfalco...@yah oo.comwrote:
dolphin wrote:
Is it a good thing that program mix C and C++?
Mix, no. You can call C routines from C++, but not the reverse.
one can call c from c++, and viceversa.
i was 'technically' wrong, but i think effect is almost same.
>
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
--
Posted via a free Usenet account fromhttp://www.teranews.co m- Hide quoted text -
- Show quoted text -
Kenneth Brody <ke******@spamc op.netwrote in message
news:46******** *******@spamcop .net...
Kenny McCormack wrote:
In article <sD************ ********@bgtnsc 04-news.ops.worldn et.att.net>,
Bill Reid <ho********@hap pyhealthy.netwr ote:
...
>object files pretty much at will. It is quite obvious that some people
>here who are experts on the return value of main() don't understand
>this.
Well said, sir! And, you might add, the ethics of casting the return
value of malloc().
Note (for the uninitiated): The "casting the return value of malloc()"
thing is an idea that is taken as gospel around here, but has no real
world traction outside of this NG. It is certainly possible to disagree
with this bit of dogma, but doing so will win you no friends around
here.
>
It's considered bad practice, as it can hide a missing #include for
the malloc-and-friends prototypes. Without those prototypes, all
bets are off as to what happens when the compiler takes what it
thinks is an int return and casts it into your pointer.
Yeah, yeah, yeah, but interestingly apropos to the original question,
if you should for some reason decide to use malloc() instead of new()
in a C++ program, you MUST cast the return value. If you don't,
you'll get a compiler error! (Which happens for many of the "little"
differences between C types, standard libraries, and semantics
when used in a C++ program.)
And of course, it is exactly this required explicit typing of return
values in C++ that precludes all the "horrible" problems (which
only occur if you make another ACTUAL mistake) of NOT casting
the value in C!
But like the use of extern "C", this is not just off-topic, but beyond
the scope of knowledge of many of the frequent posters here, as
evidenced by their struggle in this thread to come to grips with
some simple realities of real-world programming as it is and was
performed at any time in the last 15 years or so...
---
William Ernest Reid
CBFalconer <cb********@yah oo.comwrote:
Ian Collins wrote:
CBFalconer wrote:
Ian Collins wrote:
No so, C++ provides a mechanism (the extern "C" linkage specifier)
to make C++ functions callable from C.
That makes C callable from C++. Not the reverse.
It's a two way street.
No it isn't. The C++ compiler does various unspeakable things to
the function names [ ... ]
The <<extern "C">constru ct of C++ allows the programmer to
write C++ functions that are callable from C. That's a fact.
You can also write C++ functions that are not callable from C. So
what. To use such functions in a C program you have to write a
wrapper, necessarily in C++, that *is* callable from C.
It's not just a name mangling issue, the ABI's can be different
and that comes up when passing a C++ function pointer to a C library
that wants a callback.
To the OP: you can mix your C and C++ exactly as you would mix C
and, say, Fortran. Treat them as distinct languages and do what
you have to do to create working interlanguage bindings.
--
pa at panix dot com
Bill Reid wrote:
>
.... snip ...
>
Yeah, yeah, yeah, but interestingly apropos to the original question,
if you should for some reason decide to use malloc() instead of new()
in a C++ program, you MUST cast the return value. If you don't,
you'll get a compiler error! (Which happens for many of the "little"
differences between C types, standard libraries, and semantics
when used in a C++ program.)
Did you by any chance ever note the name of this newsgroup? If so,
will you kindly explain to me (and others) where in it the
character sequence "++" appears?
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
--
Posted via a free Usenet account from http://www.teranews.com
CBFalconer <cb********@yah oo.comwrote in message
news:46******** *******@yahoo.c om...
Bill Reid wrote:
... snip ...
Yeah, yeah, yeah, but interestingly apropos to the original question,
if you should for some reason decide to use malloc() instead of new()
in a C++ program, you MUST cast the return value. If you don't,
you'll get a compiler error! (Which happens for many of the "little"
differences between C types, standard libraries, and semantics
when used in a C++ program.)
Did you by any chance ever note the name of this newsgroup? If so,
will you kindly explain to me (and others) where in it the
character sequence "++" appears?
Nowhere! Which is why I am concerned about the topicality of
this previous post in this thread:
Date: Wed, 28 Mar 2007
From: CBFalconer <cb********@yah oo.com>
Newsgroups: comp.lang.c
Subject: Re: Is it a good thing that program mix C and C++?
dolphin wrote:
>
Is it a good thing that program mix C and C++?
Mix, no. You can call C routines from C++, but not the reverse.
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
---end of archived post
Actually, I'm not that concerned about the dreaded "++" as much
as the fact that it was just technically incorrect. Bad information is
ALWAYS off-topic in any group AFAIC...
So my advice is to stick with what you know. If you don't know
much, don't post much, or honestly ask for help from people who
do know. Simple enough?
---
William Ernest Reid
In article <Y0************ *********@bgtns c04-news.ops.worldn et.att.net>,
Bill Reid <ho********@hap pyhealthy.netwr ote:
(poor, misunderstood CBF wrote)
>Did you by any chance ever note the name of this newsgroup? If so,
will you kindly explain to me (and others) where in it the
character sequence "++" appears?
Nowhere! Which is why I am concerned about the topicality of
this previous post in this thread:
Date: Wed, 28 Mar 2007
From: CBFalconer <cb********@yah oo.com>
Newsgroups: comp.lang.c
Subject: Re: Is it a good thing that program mix C and C++?
dolphin wrote:
>>
Is it a good thing that program mix C and C++?
(And, again, poor, misunderstood CBF wrote)
>Mix, no. You can call C routines from C++, but not the reverse.
See, that's really the problem with being so anal about the topicality
nonsense. You can't help but eventually become hoist on your own petard.
But, of course, the regs get around this by implicitly (and from time to
time, explicitly, as in the recent fracas where good ole Heathfield
started posting a bunch of wildly OT crud) having different rules for
the regs than for the hoi polloi.
>Actually, I'm not that concerned about the dreaded "++" as much
as the fact that it was just technically incorrect. Bad information is
ALWAYS off-topic in any group AFAIC...
So my advice is to stick with what you know. If you don't know
much, don't post much, or honestly ask for help from people who
do know. Simple enough?
Good advice. But following it would mean the death of this (very
entertaining) newsgroup. We can't have that.
"Kenny McCormack" <ga*****@xmissi on.xmission.com wrote in message
news:eu******** **@news.xmissio n.com...
In article <sD************ ********@bgtnsc 04-news.ops.worldn et.att.net>,
Bill Reid <ho********@hap pyhealthy.netwr ote:
...
>>object files pretty much at will. It is quite obvious that some people
here who are experts on the return value of main() don't understand
this.
Well said, sir! And, you might add, the ethics of casting the return
value of malloc().
Note (for the uninitiated): The "casting the return value of malloc()"
thing is an idea that is taken as gospel around here, but has no real
world traction outside of this NG. It is certainly possible to disagree
with this bit of dogma, but doing so will win you no friends around here.
I was converted to uncast malloc() by the ng. Not for the reason given -
that it can mask failure to include stdlib.h. In production code that just
can't happen. My reason was to reduce visual clutter, and because a C
function only rarely needs to be cut and pasted into C++.
--
Free games and programming goodies. http://www.personal.leeds.ac.uk/~bgy1mm
In article <Rs************ *************** ***@bt.com>,
Malcolm McLean <re*******@btin ternet.comwrote :
....
>I was converted to uncast malloc() by the ng. Not for the reason given -
that it can mask failure to include stdlib.h. In production code that just
can't happen. My reason was to reduce visual clutter, and because a C
function only rarely needs to be cut and pasted into C++.
Agreed on all counts. The "mask failure" arguement is particularly
weak. It is very similar to the "if (1 == a) rather than if (a == 1)"
thing, where, this may have had some traction at some point in the deep
dark past, but nowadays any compiler worth 2 bits will catch it (i.e.,
warn about it) anyway.
The point is that is you consider the following three commonly harped on
things in this NG:
1) char a[10]; x = a[10];
2) void main()
3) char *x = (char *) malloc(10);
The first is clearly an error. The 2nd probably, and the third, really not.
Yet all three are harped upon with equal vigor, by a bunch of freaks who
don't understand the concept of degree.
On Fri, 30 Mar 2007 23:37:26 +0100, Malcolm McLean wrote:
"Kenny McCormack" <ga*****@xmissi on.xmission.com wrote in message
news:eu******** **@news.xmissio n.com...
>In article <sD************ ********@bgtnsc 04-news.ops.worldn et.att.net>,
Bill Reid <ho********@hap pyhealthy.netwr ote: ...
>>>object files pretty much at will. It is quite obvious that some people
here who are experts on the return value of main() don't understand
this.
Well said, sir! And, you might add, the ethics of casting the return
value of malloc().
Note (for the uninitiated): The "casting the return value of malloc()"
thing is an idea that is taken as gospel around here, but has no real
world traction outside of this NG. It is certainly possible to
disagree with this bit of dogma, but doing so will win you no friends
around here.
I was converted to uncast malloc() by the ng. Not for the reason given -
that it can mask failure to include stdlib.h. In production code that
just can't happen.
I have corrected a live, delivered, customer-affecting bug in 'production
code' caused by failure to include stdlib.h, masked by casting the return
from malloc. "Just can't happen" is thereby proven to be something of an
exaggeration. To the (reasonable) argument "but it must have been
seriously inexperienced programmers", I point out that's _exactly_
the audience for "Don't Cast Malloc()".
As for C++, should we not be recommending <OTuse new() <OT>?
Martin
--
Martin Golding | He who steals my code steals trash.
DoD #0236 | (Twas mine, tis his, and will be slave to thousands.)
A poor old decrepit Pick programmer. Sympathize at: fo*****@comcast .net Vancouver, WA
Malcolm McLean said:
I was converted to uncast malloc() by the ng. Not for the reason given
- that it can mask failure to include stdlib.h. In production code
that just can't happen.
When "just can't happen" relies on a basic level of human competence, we
can count on it happening at least 17 times a day, 260 days a year.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
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