loading shared libraries (linux)
Author
Hi folks
I created a shared library (.so) and put it on /usr/local/lib.
On MinGW, I went in Project -> Settings and called it there...
It compiles everything ok but the program simply doesn't run. I'm quite a newbie in programming on linux and I couldn't figure out what's going on... :-(
Does anyone know?
Hm, MinGW means "Minimal GNU for Windows", so do you run it on Linux or what?
( Do you mean Dev-C++ 5 ??? )
( Do you mean Dev-C++ 5 ??? )
On linux, you also want to run ldconfig (as root) after installing new shared libraries. Also make sure /usr/local/lib is available in your ldconfig, and in your library path.
If you want to be able to use libraries in /usr/local/lib, either add that directory to ld.so.conf OR put it in the env variable LD_LIBRARY_PATH
ldconfig is only necessary if you did the former (maybe not even then)
Mark
ldconfig is only necessary if you did the former (maybe not even then)
Mark
Author
Quote:Original post by AndiDog
Hm, MinGW means "Minimal GNU for Windows", so do you run it on Linux or what?
( Do you mean Dev-C++ 5 ??? )
It works under linux too
Quote:Original post by Roboguy
Does the library file name begain with 'lib'? If not, add it to the front.
yes, it does
Quote:Original post by hplus0603
On linux, you also want to run ldconfig (as root) after installing new shared libraries. Also make sure /usr/local/lib is available in your ldconfig, and in your library path.
Ok, it's done now. I put /usr/local/lib in the ld.so.conf file and ran ldconfig. But it can't find my .h files yet. Before that, I had created a libFile.so and a libFile.a and put both into /usr/local/lib. (are these the only files I need?)
I'm declaring my libraries like this -> #include "scene.h" (is this the correct way? I tried also this #include "File/scene.h" but it didn't work either)
Is there any step-by-step tutorial about how to create and use a library? I couldn't find one
Thanks
take this
then this
compile like this
where dynamic.cpp is the library loader (first code listing) and hellocc.cpp is the module (second).
#include <dlfcn.h>#include <iostream>using namespace std;// calling Foo demonstrates calling internal functionsextern "C" void Foo();void Bar();// Foo() calls Bar()extern "C" void Foo(){ cout << "Foo()\n"; Bar();}void Bar(){ cout << "Bar()\n";}template<class T>T function_cast(void *symbol){ assert(sizeof(void *) == sizeof(T)); union { void *symbol; T function; }cast; cast.symbol = symbol; return cast.function;}int main(){ // open module void *module = dlopen("./hello.so", RTLD_NOW|RTLD_GLOBAL); if(!module) { cerr << "error in open: " << dlerror() << "\n"; exit(-1); } // can this next 4 lines be done in a simpler way? typedef void (*Function)(); Function function; void *pointer = dlsym(module, "hello"); function = *reinterpret_cast<Function*>(&pointer); // check for errors const char *error = dlerror(); if(error) { cerr << "fatal error: " << error << "\n"; exit(-1); } // call the function function(); // close the module dlclose(module); return 0;}then this
#include <iostream>using namespace std;// look we can reference mangled variables! (below)int x = 110;extern "C"{void Foo();void hello(){ cout << "hello " << x << "\n"; Foo();}}compile like this
genjix@linux:~/media/tmp/obj/dl> g++ dynamic.cpp -ldl -export-dynamicgenjix@linux:~/media/tmp/obj/dl> g++ -o hello.so -shared hellocc.cppgenjix@linux:~/media/tmp/obj/dl> ./a.outhello 110Foo()Bar()genjix@linux:~/media/tmp/obj/dl>where dynamic.cpp is the library loader (first code listing) and hellocc.cpp is the module (second).
Author
I still don't get it :-(
I'm using classes... is it the same thing I should do? just put extern C before my methods implementations?
I'm using classes... is it the same thing I should do? just put extern C before my methods implementations?
ok you make an extern c function that returns a pointer to your class
as for implementation, well you implement this in the module (above).
#include "objectvirtualbase.h"class Object : public ObjectVirtualBase{ // ...};extern "C" ObjectVirtualBase *CreateObject(ResourceTree params){ return new ObjectVirtualBase();}as for implementation, well you implement this in the module (above).
Quote:Original post by Silent AngelYes, but why use a Windows port of something originally made for UNIX variants on a UNIX variant?Quote:Original post by AndiDog
Hm, MinGW means "Minimal GNU for Windows", so do you run it on Linux or what?
( Do you mean Dev-C++ 5 ??? )
It works under linux too
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