HOW TO - created and use shared library (.so)

[big4mil]

Hi all,

I've created my own shared library and tried to load it dynamically while my small test app is running. Unfortunately it's not working - the lib is not loaded!

In the .pro file for my lib:

TEMPLATE = lib
CONFIG += dll
TARGET = mylib

TEMPLATE = lib
CONFIG += dll
TARGET = mylib

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In the header file for my lib:

#include <Qt/qglobal.h>
 
#ifdef TEST_LIB
# define TEST_EXPORT Q_DECL_EXPORT
#else
# define TEST_EXPORT Q_DECL_IMPORT
#endif
 
class TEST_EXPORT DBConnection
{
...
};

#include <Qt/qglobal.h>

#ifdef TEST_LIB
# define TEST_EXPORT Q_DECL_EXPORT
#else
# define TEST_EXPORT Q_DECL_IMPORT
#endif

class TEST_EXPORT DBConnection
{
...
};

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Is there somthing else what I need to do?

Then in my test app I call the lib:

QLibrary myLib("mylib");

QLibrary myLib("mylib");

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If I check it with

myLib.isLoaded()

myLib.isLoaded()

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then I can see that the lib is not loaded.
Maybe it can't find the lib? Where I have to put my lib that its beeing loaded?

Any help would be great!!
Many thanks and best regrads
big4mil

[wysota]

You could place it in the same directory as the main binary.

I might be wrong here, but I think you need to wrap your methods in 'extern "C"' statements if you want to resolve symbols dynamically. And you'll need factory functions to create instances of your class.

[big4mil]

Hi wysota,

many thanks for your response. My lib is in the same directoy as the app is. I develop under SUSE Linux 10.1.

Can you give me please one simple example on how to do this? I have never done this bevor. Would be great.

What do you mean with:

And you'll need factory functions to create instances of your class.

Many thanks
big4mil

[wysota]

See the C++ dlopen mini-howto for details. QLibrary uses dlopen internally so everything there applies.

[big4mil]

that's fine - thanks for the link...I'll check that out!!


big4mil