Class libraries w/VS 2005

[djbaker]

Greetings,
I am trying to create a class library/dll with C++ and I am running
into a lot of trouble. I know that this is a C++ forum and not one
specific to windows or VS 2005 but I'm hoping someone call help me.

I would like to create a class library so that I can put classes that
I reuse a lot into their own modules. I played around with it for
awhile and had no luck. It was really easy to do in C# but C++ does
not seem to be so easy.

I saw a lot of websites referencing exporting and importing symbols
but they all seem to relate to functions. How do you decorate the
class so that you can export the whole class and create an instance of
it in the calling program.

Thanks.

 

[Guest]

Greetings,
I am trying to create a class library/dll with C++ and I am running
into a lot of trouble. I know that this is a C++ forum and not one
specific to windows or VS 2005 but I'm hoping someone call help me.

I would like to create a class library so that I can put classes that
I reuse a lot into their own modules. I played around with it for
awhile and had no luck. It was really easy to do in C# but C++ does
not seem to be so easy.

I saw a lot of websites referencing exporting and importing symbols
but they all seem to relate to functions. How do you decorate the
class so that you can export the whole class and create an instance of
it in the calling program.

You are right about this not being a C++ question, so for future
questions regarding DLLs please use a more appropriate group (I think a
win32 programming group would be the right choice). Here is a tutorial
to get you started: http://www.codeproject.com/dll/RegDLL.asp

 

[Kenneth Porter]

You are right about this not being a C++ question, so for future
questions regarding DLLs please use a more appropriate group (I think a
win32 programming group would be the right choice). Here is a tutorial
to get you started: http://www.codeproject.com/dll/RegDLL.asp

I think ghetto-izing shared library implementation should be discouraged.
Instead, consider ways to design sharable libraries that can be used on
many platforms (not just Win32). For example, is there any standardization
effort in creating syntactic linkage hints such as this kind of
import/export decorator?

For example, right now I'm working on a proprietary closed-source library
that's initially implemented as a Win32 DLL but I'd like to design it so
that it can be easily rebuilt on Linux, Solaris, Mac, etc. What's the best
way to structure one's code to accomplish that?

My approach has been to create an auxiliary header (<MyLibrary/_internal.h>
) that gets included in each public header and defines linkage macros that
get used for each class and function that needs this.

I put my headers in project/include/MyLibrary, and library clients add
project/include to their -I option. This allows me to use simple names for
headers and keeps them in a separate #include namespace. (Perhaps
project/include/Vendor/Library) would be preferable, if a vendor produces
several libraries.)

My biggest hassle so far in portable shared libraries is the use of STL
objects (particularly containers) in public classes. The MS compiler will
whine that those classes need DLL linkage. Is gcc under Linux subject to
the same problem? How can I design the classes so that I don't face this?

 

[Guest]

I think ghetto-izing shared library implementation should be discouraged.
Instead, consider ways to design sharable libraries that can be used on
many platforms (not just Win32). For example, is there any standardization
effort in creating syntactic linkage hints such as this kind of
import/export decorator?

There is very little in the way of standardising shared libraries. The
latest effort I can find on standard committee's site (N2407) is little
more than a description of the problem, an investigation of how it is
done on Windows and Linux and a suggestion of how to specify what should
be exported or not. This late in the process I would not expect it to be
included in the next version of the standard.

My biggest hassle so far in portable shared libraries is the use of STL
objects (particularly containers) in public classes. The MS compiler will
whine that those classes need DLL linkage. Is gcc under Linux subject to
the same problem? How can I design the classes so that I don't face this?

I *think* that by default everything is exported on Linux, while you
have to explicitly export it on Windows.