C 数组分配问题 / CS50 分数计算器

Question

我尝试用 CS50 学习 C 并尝试编写考试分数计算器。我试图编写如下动态代码，但出现错误。这是我的主要代码：

#include <cs50.h>
#include <stdio.h>

const int total_exam = 3 ;  // Now we are creating a constant

//Prototype
//int get_scores(void);

int main(void)
{
    // get exam scores
    int *all_scores;
    all_scores = get_scores();

    printf("Your average score is %f\n", average(total_exam, all_scores) );

}

// create an function to get exam scores of the user

int *get_scores()
{
    //get exam scores of the user

    int scores[total_exam];

    for (int i=0;i< total_exam; i++)
    {
        scores[i] =  get_int("What's your exam score?: "); // each int uses 4 byte space
    }

    return scores;
}

// create an function to calculate average

float average(int length, int array[])
{
    int sum=0;
    for (int i=0 ; i<length; i++)
    {
        sum = sum+array[i];
    }

    return sum / (float) length ;
}

但是当我尝试执行它时，我得到了如下错误。

scores_with_array.c:14:18: error: implicit declaration of function 'get_scores' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    all_scores = get_scores();
                 ^
scores_with_array.c:14:16: error: incompatible integer to pointer conversion assigning to 'int *' from 'int' [-Werror,-Wint-conversion]
    all_scores = get_scores();
               ^ ~~~~~~~~~~~~
scores_with_array.c:16:42: error: implicit declaration of function 'average' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    printf("Your average score is %f\n", average(total_exam, all_scores) );
                                         ^
scores_with_array.c:16:42: error: format specifies type 'double' but the argument has type 'int' [-Werror,-Wformat]
    printf("Your average score is %f\n", average(total_exam, all_scores) );
                                  ~~     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                  %d
scores_with_array.c:22:6: error: conflicting types for 'get_scores'
int *get_scores()
     ^
scores_with_array.c:14:18: note: previous implicit declaration is here
    all_scores = get_scores();
                 ^
scores_with_array.c:33:12: error: address of stack memory associated with local variable 'scores' returned [-Werror,-Wreturn-stack-address]
    return scores;
           ^~~~~~
scores_with_array.c:38:7: error: conflicting types for 'average'
float average(int length, int array[])
      ^
scores_with_array.c:16:42: note: previous implicit declaration is here
    printf("Your average score is %f\n", average(total_exam, all_scores) );
                                         ^
7 errors generated.

我猜这是关于数组分配的，但我无法理解。你能帮忙解决这个问题吗？提前致谢。

Answer 1

1. 为什么评论了get_scores 的原型？它导致了隐式声明问题。而且也错了，应该是int *get_scores(void);。
2. average 函数的原型不存在。 C 假设它返回一个int，这会导致更多问题。
3. 为什么要返回scores 数组，函数退出后，堆栈被破坏并且可能发生内存泄漏。像这样分配它：int *scores = malloc(sizeof(int) * total_exam)。

您的代码有点乱，所以如果还有其他问题仍然存在，我不会感到惊讶。另外，请随时通过评论要求澄清。