Missing constructor (unresolved external)

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Hello,

I have tried to include a library with a Plane class. The plane class has three constructors. The following is copied from the header file...

C++

ManipExport Plane(Point3& normal, Point3& point);
ManipExport Plane(Point3& p1, Point3& p2, Point3& p3);
ManipExport Plane(): mNormal(0,0,1), mPoint(0,0,0), mD(0.0f) {}

In my code, I can compile the following...

C++

Point3 p0, p1, p2;
p0 = mn.v[mn.f[this_face].vtx[0]].p;
p1 = mn.v[mn.f[this_face].vtx[1]].p;
p2 = mn.v[mn.f[this_face].vtx[2]].p;

Plane pln(p0, p1);

but when I try to use the the second constructor as follows I get an error

C++

Plane pln(p0, p1, p2);

I don't understand why I can compile with one constructor but not the other. I'm not even sure what I should be looking out for with this error so some hints as to what to research would be welcome...

The error is as follows.....

txt

 error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl Plane::Plane(class Point3 &,class Point3 &,class Point3 &)" (__imp_??0Plane@@QEAA@AEAVPoint3@@00@Z) referenced in function "public: void __cdecl P2PModData::Update(int)" (?Update_Q@P2PModData@@QEAAXH@Z)
1>c:\plugins\P2P.dlm : fatal error LNK1120: 1 unresolved externals

Many thanks....

Posted 27-Jul-11 21:42pm

FlurryKnox

Updated 27-Jul-11 22:04pm

Emilio Garavaglia

v2

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2 solutions

Solution 1

The third constructor is defined (has the {} at the end) and does nothing but calling the member constructors.
The first two are just declared.

You have to define them somewhere else in a CPP file as

ManipExport::ManipExport Plane(Point3& p1, Point3& p2, Point3& p3)
{
   //TODO: place here the code to initialize the members according with
   //the parameters
}

and similarly with the other one.

Posted 27-Jul-11 22:01pm

Emilio Garavaglia

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Olivier Levrey · Accepted Answer · 2011-07-27T23:47:00

If this is your own library, then Emilio's answer is the right one: you just forgot to give the implementation for that constructor.

If this is a 3rd party library, then there are several possibilities:
1- they forgot to implement that constructor and you can't do anything with it (I doubt that such a mistake could be done by serious developpers...)
2- you forgot to provide the .lib file that contains the implementation for that constructor.
3- the version of the .h you are using to compile is different from the .lib you are using for linking. If you are using different versions of a SDK, check carrefully that you are not mixing files.
4- somebody (very evil) changed the .h and added a non-existing function just to bother you...

For now I don't see anything else.