返回结构体指针

如果想让函数返回一个结构体指针，必须要malloc或者new一个空间，否则返回一个局部变量的地址，结果是无法确定的 。

#include <iostream>

typedef struct
{
    double x;
    double y;
    double z;
} calculate;

calculate *math_calculate(double a, double b);

int main() {
    calculate *cc;
    cc = math_calculate(0.5, 0.2);
    std::cout << "x : " << cc->x << "\ny : " << cc->y << "\nz : " << cc->z << std::endl;

    std::cout << "Hello, World!" << std::endl;
    free(cc);  //记得free
    return 0;
}

calculate *math_calculate(double a, double b)
{
    calculate *cal = (calculate*)malloc(sizeof(calculate));  // 必须malloc，否则报错：interrupted by signal 11: SIGSEGV
    cal->x = a + b;
    cal->y = a - b;
    cal->z = a * b;

    return cal;
}