initializing array pointer to a struct

Question

I get the Error run-time check failure #3, and i have to initialize P and i know why but not how to do it.

Points is supposed to be a variable 2D array like float* points[3] for testing purposes its constant for now.

CVAPI(CvPOSITObject*)  lvCreatePOSITObject( float points[5][3], int point_count )
{
    CvPoint3D32f* P; //array of structs with int x,y,z 
    for(int i = 0; i< point_count; i++)
    {
        P[i].x = points[i][0];
        P[i].y = points[i][1];
        P[i].z = points[i][2];
    }
    return cvCreatePOSITObject(P,point_count);
}

What does cvCreatePOSITObject() do? This is essential to know, for deciding which solution to take, as there are multiple. — alk
– alk, Commented Nov 4, 2015 at 12:44
a value of type void* cannot be used to initialize an entity of type CvPoint3D32f, also is it possible to use malloc(point_count, sizeof(CVPoint3D32f))? it creates a opencv structure from points — Eumel
– Eumel, Commented Nov 4, 2015 at 12:45
malloc(point_count, sizeof(CVPoint3D32f)) should have read calloc(point_count, sizeof(CVPoint3D32f))? — alk
– alk, Commented Nov 4, 2015 at 12:49

MikeCAT · Accepted Answer · 2015-11-04 12:43:09Z

1

I don't know much about OpenCV, but I think you should allocate some memory to store the data.

#include <stdlib.h> // add this to the head of the file to use malloc

CVAPI(CvPOSITObject*)  lvCreatePOSITObject( float points[5][3], int point_count )
{
    CvPoint3D32f* P; //array of structs with int x,y,z
    P = malloc(sizeof(CvPoint3D32f) * point_count); // allocate some memory
    for(int i = 0; i< point_count; i++)
    {
        P[i].x = points[i][0];
        P[i].y = points[i][1];
        P[i].z = points[i][2];
    }
    return cvCreatePOSITObject(P,point_count);
}

This code may be bad because this may not free the allocated buffer.

answered Nov 4, 2015 at 12:43

MikeCAT

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3 Comments

Eumel Over a year ago

malloc says: a value of type void* cannot be used to initialize an entity of type CvPoint3D32f freeing the memory happens in another function

alk Over a year ago

@Eumel: Mind the * in CvPoint3D32f* P;!

Eumel Over a year ago

oh yes there should be a * there

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