.dll question

.dll question

[Paul G.]

Hi folks,

	Try not to add to noise for this list unless it seems necessary for something I am 
currently porting.  That is my apology ahead of time.

	Does msvc/c++ load .dlls generated using gcc -shared  -mno-cygwin?

	I've not ever had msvc/c++ so can't say one way or the other.

	Thanks,

		Paul G.

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Re: .dll question

[Dan Kegel]

David Starks-Browning wrote:
>>>	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
>>>does Microsofts'  method of name mangling prohibit such things?
>>
>>No it can't. In general, C++ compilers don't interoperate. The C++-Lite
>>FAQ has a section on this.
>>
>>From memory, the issues are:
>>*name mangling
>>*VMT layout
>>*new[] management
>>*exception handling
>>
>>If you want to use cygwin C++ from MSVC, write some C bindings for the
>>code.
> 
> ... All the FAQ says about this is the following:
> 
>   Q.  Can I mix objects compiled with msvc++ and gcc?
> 
>   A.  Yes, but only if you are combining C object files. MSVC C++ uses
>       a different mangling scheme than GNU C++, so you will have
>       difficulties combining C++ objects.
> 
> I'd like to include the extra detail that Robert goes into, if it's
> correct.  Does anyone know for sure?

Any discussion of these issues isn't complete without mentioning
the fact that you can't even mix objects compiled by gcc2.x
and gcc3.x.  This was caused by the switchover as of gcc3.x to the standard
C++ ABI defined at http://www.codesourcery.com/cxx-abi/
That document defines very carefully all the issues Robert writes
about, I think.  All C++ compilers for Linux should now be following
that standard.  See also http://gcc.gnu.org/gcc-3.2/c++-abi.html

Also, I have some extra detail about name mangling in MSVC6 and gcc2.x
at http://www.kegel.com/mangle.html
It's three years old but may still be useful.

- Dan

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Re: .dll question

[David Starks-Browning]

On  3 Oct 02, Robert Collins writes:
> On Thu, 2002-10-03 at 09:13, Paul G. wrote:
> 
> > 	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
> > does Microsofts'  method of name mangling prohibit such things?
> 
> No it can't. In general, C++ compilers don't interoperate. The C++-Lite
> FAQ has a section on this.
> 
> >From memory, the issues are:
> *name mangling
> *VMT layout
> *new[] management
> *exception handling
> 
> If you want to use cygwin C++ from MSVC, write some C bindings for the
> code.

Apologies for this blast from the past.  As you can see I'm nearly 7(!)
months behind in the mailing list.  (But I'm catching up!)

All the FAQ says about this is the following:

  Q.  Can I mix objects compiled with msvc++ and gcc?

  A.  Yes, but only if you are combining C object files. MSVC C++ uses
      a different mangling scheme than GNU C++, so you will have
      difficulties combining C++ objects.

I'd like to include the extra detail that Robert goes into, if it's
correct.  Does anyone know for sure?

Thanks for your help.

Regards,
David
(Cygwin FAQ maintainer)


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Re: .dll question

[Shankar Unni]

On 10/2/2002 4:19 PM, Robert Collins wrote:

> No it can't. In general, C++ compilers don't interoperate. The C++-Lite
> FAQ has a section on this.
> From memory, the issues are:
> *VMT layout
 > [..]

And before someone jumps up and asks why this can't be reverse 
engineered - apart from the general difficulty of the task, there are 
even potential patent issues, as Microsoft claims to have patented some 
clever VMT layout and optimization algorithms that they use for VC++. 
It's unclear whether another compiler can use the same algorithm (to 
match VC++) without running afoul of these patents..




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Re: .dll question

[Paul G.]

Thank you, Rob.

On 3 Oct 2002 at 9:19, Robert Collins wrote:

> On Thu, 2002-10-03 at 09:13, Paul G. wrote:
> 
> > 	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
> > does Microsofts'  method of name mangling prohibit such things?
> 
> No it can't. In general, C++ compilers don't interoperate. The C++-Lite
> FAQ has a section on this.
> 
> From memory, the issues are:
> *name mangling
> *VMT layout
> *new[] management
> *exception handling
> 
> If you want to use cygwin C++ from MSVC, write some C bindings for the
> code.
> 
> Rob

		Paul G.

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Re: .dll question

[Paul G.]

Thank you, Rob.

On 3 Oct 2002 at 9:19, Robert Collins wrote:

> On Thu, 2002-10-03 at 09:13, Paul G. wrote:
> 
> > 	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
> > does Microsofts'  method of name mangling prohibit such things?
> 
> No it can't. In general, C++ compilers don't interoperate. The C++-Lite
> FAQ has a section on this.
> 
> From memory, the issues are:
> *name mangling
> *VMT layout
> *new[] management
> *exception handling
> 
> If you want to use cygwin C++ from MSVC, write some C bindings for the
> code.
> 
> Rob

		Paul G.

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Re: .dll question

[Robert Collins]

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On Thu, 2002-10-03 at 09:13, Paul G. wrote:

> 	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
> does Microsofts'  method of name mangling prohibit such things?

No it can't. In general, C++ compilers don't interoperate. The C++-Lite
FAQ has a section on this.

From memory, the issues are:
*name mangling
*VMT layout
*new[] management
*exception handling

If you want to use cygwin C++ from MSVC, write some C bindings for the
code.

Rob
-- 
---
GPG key available at: http://users.bigpond.net.au/robertc/keys.txt.
---

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Re: .dll question

[Paul G.]

Hi folks,

	Thank you, ahead of time, for your consideration and your replies.

On 2 Oct 2002 at 17:09, Phil Dempster wrote:

> > Try not to add to noise for this list unless it
> > seems necessary for something I am currently
> > porting.  That is my apology ahead of time.
> > 
> > Does msvc/c++ load .dlls generated using
> > gcc -shared  -mno-cygwin?
> 
> You can use gcc compiled DLLs with MSVC compiled
> executables.  However, you won't be able to debug them
> in the MSVC IDE.

	Thank you, Phil.  Thank you again for that clarification.

	On a related note, can Cygwin generate c++ .dlls which are loadable by msvc++ or 
does Microsofts'  method of name mangling prohibit such things?

	Thanks again for your input folks.

	Paul G.

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Re: .dll question

[Igor Pechtchanski]

On Wed, 2 Oct 2002, [iso-8859-1] Phil Dempster wrote:

> > Try not to add to noise for this list unless it
> > seems necessary for something I am currently
> > porting.  That is my apology ahead of time.
> >
> > Does msvc/c++ load .dlls generated using
> > gcc -shared  -mno-cygwin?
>
> You can use gcc compiled DLLs with MSVC compiled
> executables.  However, you won't be able to debug them
> in the MSVC IDE.
>
> Hope this helps
> Phil

Phil,
ISTR that there were some differences in function name mangling between
gcc and MSVC...
	Igor
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Re: .dll question

[Phil Dempster]

> Try not to add to noise for this list unless it
> seems necessary for something I am currently
> porting.  That is my apology ahead of time.
> 
> Does msvc/c++ load .dlls generated using
> gcc -shared  -mno-cygwin?

You can use gcc compiled DLLs with MSVC compiled
executables.  However, you won't be able to debug them
in the MSVC IDE.

Hope this helps
Phil

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