I'm not a frequent user of Linux and I think I did something wrong.
This is the code for a test dynamic library ".so" I'm generating.
class InternalClass
{
public:
int Function(){ return 10; }
};
extern "C"
{
int WrapperFunctionSimple() { return 10; }
void WrapperCreateInstance() {InternalClass* item = new InternalClass(); delete item; }
}
The compilation fails with the following error:
g++ -Wall -fexceptions -O2 -c /home/lidia/compartida/TestLibrary/TestLibrary/main.cpp -o obj/Release/main.o
g++ -shared obj/Release/main.o -o bin/Release/libTestLibrary.so -s
/usr/lib64/gcc/x86_64-suse-linux/7/../../../../x86_64-suse-linux/bin/ld: obj/Release/main.o: warning: relocation against `_Znwm@@GLIBCXX_3.4' in read-only section `.text'
/usr/lib64/gcc/x86_64-suse-linux/7/../../../../x86_64-suse-linux/bin/ld: obj/Release/main.o: relocation R_X86_64_PC32 against symbol `_Znwm@@GLIBCXX_3.4' can not be used when making a shared object; recompile with -fPIC
/usr/lib64/gcc/x86_64-suse-linux/7/../../../../x86_64-suse-linux/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
I tried with -fPIC as suggested and it compiles. But when using this library, It cannot be loaded when I add that last function:
void WrapperCreateInstance() {InternalClass* item = new InternalClass(); delete item; }
The problem is using the InternalClass, without this function everything works.
I'm using VirtualBox. I installed OpenSUSE 64bit, the app that uses the library is also 64bit. In another linux distribution (Mint), with exactly the same project and settings (without fPIC), it can be compiled. When I use that library (.so) it works in SUSE.
I'm also using :
What am I doing wrong? This seems like something advanced Linux users could help me understand.
EDIT: To add more information, this can compile in Ubuntu with the same settings. Not in SUSE
This usually means that you don't have all functions defined. A better error message would be nice, but this is what we have for now. Define all used functions, and you should be good to go.
It happened to me when I used GCC to compile a CPP file. So for C++ files use g++ only, and obviously not GCC, which is meant for c files.
To me it happened, if one library (A) depends on another one (B) and library A was linked before library B. The solution is to link library B first and then A.