Function parameter problem

Christoffer Green · 2012-10-23T08:05:30

Hello! I am new to angelscript and I have a problem where the first parameter to a registered object method is always the object itself. What can I do to fix this? Here is some example code: [source lang="cpp"]void MessageCallback_(const asSMessageInfo *msg, void *param) { const char *type = "ERR "; if( msg->type == asMSGTYPE_WARNING ) type = "WARN"; else if( msg->type == asMSGTYPE_INFORMATION ) type = "INFO"; printf("%s (%d, %d) : %s : %s\n", msg->section, msg->row, msg->col, type, msg->message); } [/source] [source lang="cpp"]class Person { public: Person() {} void printTwoInts(int a, int b); void AddRef() {} void ReleaseRef() {} static Person *refFactory() { return new Person(); }; }; Person::printTwoInts(int a, int b){ cout (int)this " " a " " b endl; } (had to remove left arrows for cout in the above code above) [/source] [source lang="cpp"]int main() { asIScriptEngine *scriptEngine = asCreateScriptEngine(ANGELSCRIPT_VERSION); int r = scriptEngine->SetMessageCallback(asFUNCTION(MessageCallback_), 0, asCALL_CDECL);assert( r >= 0 ); r = scriptEngine->RegisterObjectType("Person", sizeof(Person), asOBJ_REF); assert( r >= 0 ); r = scriptEngine->RegisterObjectBehaviour("Person", asBEHAVE_FACTORY, "Person @f()", asFUNCTION(Person::refFactory), asCALL_CDECL); assert( r >= 0 ); r = scriptEngine->RegisterObjectBehaviour("Person", asBEHAVE_ADDREF, "void f()", asMETHOD(Person, AddRef), asCALL_THISCALL); assert( r >= 0 ); r = scriptEngine->RegisterObjectBehaviour("Person", asBEHAVE_RELEASE, "void f()", asMETHOD(Person, ReleaseRef), asCALL_THISCALL); assert( r >= 0 ); r = scriptEngine->RegisterObjectMethod("Person", "void printTwoInts(int a, int b)", asMETHOD(Person, printTwoInts), asCALL_THISCALL);assert( r >= 0 ); CScriptBuilder builder; r = builder.StartNewModule(scriptEngine, "Test"); assert( r >= 0 ); r = builder.AddSectionFromFile("./Test.as"); assert( r >= 0 ); r = builder.BuildModule();if( r < 0 ); assert( r >= 0 ); asIScriptModule *mod = scriptEngine->GetModule("Test"); asIScriptFunction *func = mod->GetFunctionByDecl("void main()"); asIScriptContext *ctx = scriptEngine->CreateContext(); ctx->Prepare(func); r = ctx->Execute(); return 0; }[/source] The Test.as script is as: [source lang="cpp"]void main() { Person p; p.printTwoInts(999,55); }[/source] When run this outputs: "8097752 8097752 999" Meaning the first parameter is not an int but an object pointer. So the function calling is done wrong? But when I try to change asCALL_THISCALL to asCALL_CDECL, asCALL_STDCALL, asCALL_CDECL_OBJLAST, asCALL_CDECL_OBJFIRST or asCALL_GENERIC I get an error code: -24. -24 is asWRONG_CALLING_CONV but I don't know how to fix that. Do I need to use something else other then asMETHOD when registering the function? If so what? I am using mingw 4.7.0. Thanks.

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Started by Heuristics September 23, 2012 07:17 AM

18 comments, last by Heuristics 11 years, 6 months ago

WitchLord

4,834

October 12, 2012 11:53 PM

I've updated the code::blocks project files in revision 1431.

I tried installing mingw too, but the installer from the mingw site appears to only install version 4.6, not 4.7. The mingw version that comes with code::blocks is even older.

Where do you get version 4.7 from? Is it necessary to download each file manually?

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Heuristics

147

Author

October 13, 2012 07:20 AM

I think I did something like getting this file: http://sourceforge.net/projects/mingw/files/Installer/mingw-get-inst/mingw-get-inst-20120426/
and during the installation I picked "download latest repository catalogues". From checking now that appears to download mingw 4.7

WitchLord

4,834

October 13, 2012 05:41 PM

Thanks, I'll give that a try.

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WitchLord

4,834

October 14, 2012 05:37 PM

I'm making some progress.

However, there are more changes in MinGW 4.7 than I had expected. It will be a while longer before I can complete all the changes and tests needed to get this fully working.

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WitchLord

4,834

October 14, 2012 11:30 PM

It appears that I made a break-through. As of revision 1435, all tests pass successfully with MinGW32 4.7.0 and 4.6.2.

The MinGW developers made some strange choices with the new ABI. For the most part they seem to have wanted to more closely follow the MS ABI, most likely to make it easier to use the many dlls available, but in some cases they ended up with something that is neither like the MS ABI nor the GNUC ABI. This doesn't make any sense at all to me, and quite frankly I believe they may very well change it again with a future version.

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Heuristics

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Author

October 15, 2012 06:26 PM

Great to hear!

I tested it as well with my own code and it does indeed appear to work. Thanks a lot, I very much appreciate the very quick fix to this issue. I now get to use fancy c++11 features with angelscript

Strange about the ABI though, but then again I know little about such things. But I do know that it is sometimes hard to understand how the GNU devs pick their priorities.

Heuristics

147

Author

October 21, 2012 07:14 PM

Hello again.

I extended my little test code with using a class as value instead of as reference and then it crashes in mingw 4.7.0 but works fine in 4.6.0. Perhaps this is another problem? (or I might just be doing it wrong

)

Here is the modified example: http://pastebin.com/27BzeQcy

WitchLord

4,834

October 21, 2012 08:58 PM

That it works on 4.6, but not on 4.7 does seem to indicate the problem is related to the changes done in MinGW, but I'll need to investigate it to be sure.

I'll let know when I figure it out. Thanks.

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WitchLord

4,834

October 21, 2012 11:32 PM

The problem was not with MinGW after all.

You've implemented the constructor and destructor incorrectly. They should be global functions, or static members, and registered with asCALL_CDECL_OBJLAST instead of asCALL_THISCALL.

It didn't crash on MinGW 4.6.0 because before 4.7 the thiscall was practically identical to the cdecl calling convention.



class Person {

    public:

	    Person() {cout<<(int)this<<endl;this->counter = 1;}

	    static void Constructor(void *memory) {new(memory) Person();}

	    static void Destructor(void *memory) {((Person*)memory)->~Person();}

	    void printTwoInts(int a, int b) { cout << (int)this << " " << a << " " << b << endl; }

	    void AddRef() {cout<<this<<" 1 "<<this->counter;}

	    void ReleaseRef() {cout<<this<<" 2 "<<this->counter;}

	    static Person *refFactory() {

		    return new Person();

	    };

	    int counter;

};



void main()

{

  ...

  asIScriptEngine *engine = asCreateScriptEngine(ANGELSCRIPT_VERSION);

  engine->SetMessageCallback(asMETHOD(COutStream,Callback), &out, asCALL_THISCALL);

  r = engine->RegisterObjectType("Person", sizeof(Person), asOBJ_VALUE | asOBJ_POD); assert( r >= 0 );

  r = engine->RegisterObjectBehaviour("Person", asBEHAVE_CONSTRUCT, "void f()", asFUNCTION(Person::Constructor), asCALL_CDECL_OBJLAST); assert( r >= 0 );

  r = engine->RegisterObjectBehaviour("Person", asBEHAVE_DESTRUCT, "void f()", asFUNCTION(Person::Destructor), asCALL_CDECL_OBJLAST); assert( r >= 0 );



  r = engine->RegisterObjectMethod("Person", "void printTwoInts(int a, int b)", asMETHOD(Person, printTwoInts), asCALL_THISCALL);assert( r >= 0 );

}

Regards,
Andreas

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Heuristics

147

Author

October 23, 2012 08:05 AM

Ah!

That makes sense, I feel a bit silly now

(was mislead by it not crashing on 4.6.0). Sorry about that. But thank you very much for your help again!

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