Is it a good thing that program mix C and C++?
Mar 28 '07
45  2075 
Richard Heathfield wrote:
Ian Collins said:
>>Richard Heathfield wrote:
>>>Ian Collins said:
CBFalcone r wrote:
>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.
No so, C++ provides a mechanism (the extern "C" linkage specifier) to
make C++ functions callable from C.
No, it doesn't. It makes C functions callable from C++.
All together now: oh yes it does!
I can find no evidence in ISO/IEC 9899 to support your claim - or, for
that matter, my own claim that it makes C functions callable from C++.
I therefore withdraw that claim. Please provide chapter and verse from
ISO/IEC 9899 for extern "C" being a mechanism to C++ functions callable
from C, or alternatively follow my lead by withdrawing your claim.
That's almost as daft as asking me to show where ISO/IEC 9899 states
that the sky is blue.
--
Ian Collins.
On Mar 28, 10:30 am, SM Ryan <wyrm...@tang o-sierra-oscar-foxtrot-
tango.fake.orgw rote:
CBFalconer <cbfalco...@yah oo.comwrote:
# Ian Collins wrote:
# CBFalconer wrote:
# >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.
# >
# 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.
That comes as a real shock to those of us who do so, by deviously
following the extern "C" rules explicitly intended to allow this.
Albeit at great danger in either case.
For instance, you cannot mix try/catch with setjmp()/longjmp().
Are you absolutely certain that setjmp()/longjmp() are not used
anywere in the C routines (including library calls)?
How about try/catch?
There are other dangers as well.
Ian Collins said:
Richard Heathfield wrote:
<snip>
>Please provide chapter and
verse from ISO/IEC 9899 for extern "C" being a mechanism to [make]
C++ functions callable from C, or alternatively follow my lead by
withdrawing your claim.
That's almost as daft as asking me to show where ISO/IEC 9899 states
that the sky is blue.
And indeed, as I look out of my window, I see that the sky is not blue.
It's quite a deep black, actually.
Had ISO/IEC 9899 guaranteed the blueness of the sky, I would have had
cause for complaint about non-conformance. As it doesn't offer any such
guarantee, however, I fail to see the relevance of your objection.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: rjh at the above domain, - www.
Richard Heathfield wrote:
Ian Collins said:
>>Richard Heathfield wrote:
<snip>
>>>Please provide chapter and
verse from ISO/IEC 9899 for extern "C" being a mechanism to [make]
C++ functions callable from C, or alternatively follow my lead by
withdrawin g your claim.
That's almost as daft as asking me to show where ISO/IEC 9899 states
that the sky is blue.
And indeed, as I look out of my window, I see that the sky is not blue.
It's quite a deep black, actually.
Had ISO/IEC 9899 guaranteed the blueness of the sky, I would have had
cause for complaint about non-conformance. As it doesn't offer any such
guarantee, however, I fail to see the relevance of your objection.
There is a world beyond ISO/IEC 9899, so just as ISO/IEC 9899 doesn't
guarantee the blueness of the sky, it doesn't say anything regarding how
other languages make their functions callable from C.
--
Ian Collins.
Ian Collins said:
There is a world beyond ISO/IEC 9899
Chapter and verse, please. :-)
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: rjh at the above domain, - www.
Richard Heathfield wrote:
Ian Collins said:
>>There is a world beyond ISO/IEC 9899
Chapter and verse, please. :-)
We are still waiting for the first draft of the ISO "Life, the Universe
and Everything" specification. I'll get back to you when it is released....
--
Ian Collins.
In article <57************ *@mid.individua l.net>,
Ian Collins <ia******@hotma il.comwrote:
>>>There is a world beyond ISO/IEC 9899
>Chapter and verse, please. :-)
>We are still waiting for the first draft of the ISO "Life, the Universe
and Everything" specification. I'll get back to you when it is released....
There was a W3C specification for this, but it never got past the
Candidate Recommendation stage because of the lack of two compatible
implementations .
-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
Richard Heathfield <rj*@see.sig.in validwrites:
Ian Collins said:
>Richard Heathfield wrote:
>>Ian Collins said:
CBFalcone r wrote:
[...]
>>>>>Mix, no. You can call C routines from C++, but not the reverse.
No so, C++ provides a mechanism (the extern "C" linkage specifier) to
make C++ functions callable from C.
No, it doesn't. It makes C functions callable from C++.
All together now: oh yes it does!
I can find no evidence in ISO/IEC 9899 to support your claim - or, for
that matter, my own claim that it makes C functions callable from C++.
I therefore withdraw that claim. Please provide chapter and verse from
ISO/IEC 9899 for extern "C" being a mechanism to C++ functions callable
from C, or alternatively follow my lead by withdrawing your claim.
The lack of any mention of this in ISO/IEC 9899 indicates that the
claim is off-topic. It does not indicate that it should be withdrawn,
<OT>particularl y since the claim happens to be correct</OT>.
Withdrawing a claim tends to imply that it's untrue, not merely that
it should not have been made.
If your call to withdraw the claim was not intended to imply that the
claim is untrue, then I have no argument (except for your potentially
misleading choice of words).
--
Keith Thompson (The_Other_Keit h) 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."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
Ian Collins wrote:
CBFalconer wrote:
>Ian Collins wrote:
>>CBFalconer wrote:
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.
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 in order to handle overloading, i.e. it creates
multiple names for functions depending on the types of their
parameters. It calls these functions with similarly adorned
names. This is all necessary to make C++ work. A C header file
can conditionally (on __cplusplus) include the extern "C" { .... }
wrapper on the function prototypes, which tells the C++ compiler
that these calls are unadorned. Now the linker can work.
Since the C++ object code uses those adorned names, the C compiler
has no way of generating calls to them. If you try to compile the
C code with a C++ compiler you have other problems, because they
are different languages.
--
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 wrote:
Ian Collins wrote:
>>CBFalconer wrote:
>>>Ian Collins wrote:
CBFalcone r wrote:
>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.
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 in order to handle overloading, i.e. it creates
multiple names for functions depending on the types of their
parameters. It calls these functions with similarly adorned
names. This is all necessary to make C++ work. A C header file
can conditionally (on __cplusplus) include the extern "C" { .... }
wrapper on the function prototypes, which tells the C++ compiler
that these calls are unadorned. Now the linker can work.
extern "C" linkage suppresses name mangling for functions compiled as
C++. The rules of C++ permit only one instance of any extern "C"
function name, they can not be overloaded and they can be called from C.
Since the C++ object code uses those adorned names, the C compiler
has no way of generating calls to them.
It dose if they are declared extern "C" because the functions are not
mangled.
--
Ian Collins. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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