Create and use library Qt creator

[posixprogrammer]

Hi all,
I create a shared object ( dynamic library) by Eclipse IDE and I can use this *.so for Qt Creator, Eclipse. But when I create a shared object by Qt Creator, I can not use it on both Eclipse , Qt Creator. I use "ldd" command to check it, I see no problem.
Please tell me why?
Thank you

[posixprogrammer]

If we mix source code C, C++ in library, executable project for header file, please note key word:
#ifdef __cplusplus
extern "C" {
#endif
//prototype here
#ifdef __cplusplus
}
#endif