Question

当运行get_poly函数时，它会给我一个分段错误。一些占位符和东西是尝试修复错误。我真的不知道造成这种情况的原因。

//Weston Sapusek, cop3515
//This program outputs the polynomial of a number given coefficients for each exponent.

#include <stdio.h>
#include <math.h>

void get_poly(double *coeff, int N);
void eval_poly(double *coeff, double base, int N);

int main(void)
{
    int N; //max exponent
    double base;

    printf("Please enter the power of your polynomial: ");
    scanf("%d", &N);

    printf("Please enter the base number: ");
    scanf("%lf", &base);

    double a[N];
    double *coeff;
    coeff = &a[0];

    get_poly(coeff, N);
    coeff = 0; //reset the coefficient pointer

    eval_poly(coeff, base, N);  
    return 0;
}

void get_poly(double *coeff, int N) {
    printf("Enter %d coeffecients of the function, in order: ", N);
    int i = 0;
    double placeholder;
    for (i = 0; i < N; i++){
        scanf("%lf", &placeholder);
        *coeff = placeholder;
        coeff++;
    }
}

void eval_poly(double *coeff, double base, int N)
{
    int i = 0;
    double x = 0; //total

    for (i = 0; i < N; i++){
        x+= *coeff * base;
    }
    printf("%lf", x);
}

Answer 1

这看起来像有问题的代码：

get_poly(coeff, N);
coeff = 0; //reset the coeffecient pointer

eval_poly(coeff, base, N);

在<{1}}为NULL之后，您重置系数指针。然后调用coeff并取消引用eval_poly函数内的NULL指针coeff。这导致了段错误。

Answer 2

只需删除此行：

  coeff = 0; //reset the coeffecient pointer

coeff未被get_poly更改，因为它是按值发送的（尽管它是指针）

设置coeff = 0;使其指向无效的内存地址。

使用指向数组的指针时出现分段错误

2 个答案: