OpenGL中glutMouseFunc函数问题

Question

我想在MouseFunc中给一个结构体中成员赋值，但是一直报错Segmentation fault (core dumped)，用gdb查了一下是这个赋值语句的问题，以下是代码

#include<GL/glut.h>
#include<stdio.h>
#include<math.h>
#include<malloc.h>
#include<stdlib.h>

struct PointD
{
        int x;
        int y;
        PointD* next;
};

struct PointU
{
        int x;
        int y;
        PointU* next;
};

struct PointD* D=NULL;
struct PointU* U=NULL;

void MouseClick(int btn,int state ,int x,int y)
{
        x=ReCoordinate(x);
        y=ReCoordinate(y);
        x=x-half;
        y=half-y;
        if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
         {
                 D->x=x;  //报错语句
                 D->y=y;//报错语句
                 PointD* p=NULL;
                 p=(PointD*)malloc(sizeof(PointD));
                 D->next=p;//报错语句
                 D=D->next;
                 pressed=1;
         }
       else if(btn==GLUT_LEFT_BUTTON && state==GLUT_UP && pressed==1)
        {
                U->x=x;
                U->y=y;
                PointU* q=NULL;
                q=(PointU*)malloc(sizeof(PointU));
                U->next=q;
                U=U->next;
                pressed=0;
                glutPostRedisplay;
        }
}
int main(int argc,char** argv)
{

        D=(struct PointD*)malloc(sizeof(PointD));
        U=(struct PointU*)malloc(sizeof(PointU));
        glutInit(&argc,argv);
        glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE|GLUT_DEPTH);
        glutInitWindowPosition(100,100);
        glutInitWindowSize(800,800);
        int half=400;
        glutCreateWindow("TEST");
        glMatrixMode(GL_PROJECTION);
        glOrtho(-half,half,-half,half,-half,half);
        glutDisplayFunc(&display);
        glutMouseFunc(MouseClick);
        glutMainLoop();
        return 0;
}

Answer 1

https://blog.csdn.net/m0_37876745/article/details/78147046