Question

I am using VS2010 on a C++ project using opencv. Many of the calls in opencv have default parameters for the last few parameters to functions. However, when omitting these parameters in function calls, Visual Studio complains and says "functionname: too few arguments for call

Is this a quirk of visual studio? Is it a setting somewhere that I can turn off? Why is this occurring. The code compiles fine under g++.

edit

As an example,

#include <cv.h>
#include <cxcore.h>

int main()
{

    CvMat *rotation_vector = cvCreateMat(3,3, CV_64FC1);
    double rotation[] = { 0, 1, 0,
                -1, 0, 0,
                0, 0, 1 };

    cvInitMatHeader(rotation_vector, 3, 3, CV_64FC1, rotation, 2147483647); // works
        cvInitMatHeader(rotation_vector, 3, 3, CV_64FC1, rotation); // doesn't work
    return 0;
}

Answer 1

The declaration for cvInitMatHeader() is this:

CVAPI(CvMat*) cvInitMatHeader( CvMat* mat, int rows, int cols, int type,
    void* data CV_DEFAULT(NULL), int step CV_DEFAULT(CV_AUTOSTEP) ); 

The definition of CV_DEFAULT looks something like this:

#ifdef __cplusplus
    #define CV_DEFAULT(val) = val
#else
    #define CV_DEFAULT(val)
#endif

So it appears that your Visual C++ compiler is actually compiling in C mode and not C++ mode. In C mode, __cplusplus would not be defined, so CV_DEFAULT expands to nothing. Therefore, it appears that the function declaration does not have default parameters.

Check your project settings and make sure you’re compiling the code in C++ mode. That is, ensure that the /Tp or /TP compiler switch is enabled. You should also make sure your C++ files have the .cpp file extension.