Question

我有一个循环，涉及C中动态分配的数组。由于某种原因，它在flag递增7次后崩溃。在重新分配数组大小之前，这种情况没有发生。这是代码：

for (int i = 0; i < length-1; i++) 
{

    if (audio_samples[i] > threshold  && run) 
    {

        *event_flags = (int*)realloc(*event_flags, sizeof(int)*(flag+1)); // reallocate the size of the array
        *event_flags[flag] = i;
        // printf("FLAG CREATED! %i\n ", i);
        printf("EVENT FLAG %i  %i\n",flag, *event_flags[flag] );
        if (flag >5) {
            printf("%d\n", i);
        }

        flag++;
        run = false;
    }

有什么想法吗？请记住，数组的大小确实与长度相同。以下是我的错误示例： enter image description here

编辑1

文件一：

   int *event_positions = (int *) malloc(1 * sizeof(int)); // let us start with 1 and then add more within the method. This should continue until we have all the flags we want.  
   int number_of_flags = event_extractor(vocal_data, size, event_positions);

文件二：

 float g_THRESHOLD_FACTOR = 2.3; // THIS INCREASES THE THRESHOLD VALUE.


 int event_extractor (int *audio_samples, unsigned int size_of_audio ,int *event_flags)
 {

int length = (int)size_of_audio;


// * * * * * * * * * * * * * * * * * * 
// RECTIFY VALUES (MAKE ABSOLUTE) (MAKE ALL POSITIVE)
int *rectified_audio = (int *) malloc(length * sizeof(int)); // I took this line from wave header reader. The number is the number of samples of the hip hop track.
make_values_absolute(audio_samples, length, rectified_audio);


   // If I convert to signed ints here would the method run more efficiently?   

// * * * * * * * * * * * * * * * * * * * *
// LOW PASS FILTER
int *lopass_samples = (int *) malloc(length * sizeof(int)); // I took this line from wave header reader. The number is the number of samples of the hip hop track.
lopass(rectified_audio, length,0.5, lopass_samples);



int number_of_flags = apply_threshold (lopass_samples, length, &event_flags);


printf("\n\n\n NUMBER OF EVENTS AAAA  --- %d\n", number_of_flags);

for (int i = 0; i < number_of_flags; i++) {
    printf("FLAG %i  -- %d \n", i, event_flags[i]);
}



return number_of_flags;
 }


 int apply_threshold (int *audio_samples, unsigned int size_of_audio, int **event_flags)
  {


int flag = 0; // this will be the number of flags that I have 
bool run = true; // this will make sure that a minimum amount of time passes before I grab another flag. It's a guard.
int counter = 0; // this is the counter for the above guard. 





printf("\n\nCURRENT MINIMUM TIME:  20100 SAMPLES \n\n");

// event_flags[0] = 1; // this first one is a dud. within the loop we will automatically start adding flags


int threshold = calculate_threshold_value(audio_samples, size_of_audio);

printf("\n\n this is the threshold %d \n\n", threshold);

int length = (int)size_of_audio;

printf("LENGTH OF VOCAL AUDIO %d \n", length  );  


for (int i = 0; i < length-1; i++) 
{

    if (audio_samples[i] > threshold  && run) 
    {

        // ** is this realloc working ?
        // event_flags = (int*)realloc(event_flags, sizeof(int) * (flag+1));
        *event_flags = (int*)realloc(*event_flags, sizeof(int)*(flag+1)); // reallocate the size of the array
        *event_flags[flag] = i;
        // printf("FLAG CREATED! %i\n ", i);
        printf("EVENT FLAG %i  %i\n",flag, *event_flags[flag] );
        if (flag >5) {
            printf("%d\n", i);
        }

        flag++;
        run = false;




    }   

    if (!run) {
        counter++;
        if (counter > 20100) { // hardcode minimum size for now. 
            counter = 0;
            run=true;
        }
    }

}

printf("\n\n\n NUMBER OF EVENTS --- %d\n", flag);

for (int i = 0; i < flag; i++) {
    printf("FLAG %i  -- %d\n", i, *event_flags[i]);
}



printf("\nFIVE samples before and after my second flag: \n 0 should indicate a reach in the threshold\n");

for (int i = 0; i <10 ; i++) {
    printf("VOCAL SAMPLE %i  %i \n", i-5,audio_samples[*event_flags[1]+i-5] );
}


return flag;
 }

Answer 1

首先，你不应该转换realloc。

然后，如果我认为该变量的类型是int*

*event_flags[flag] = i;

有一个*太多了吗？

编辑：在您发表演讲后发表评论。

因此，如果您的event_flags有效int**，那么您的确走错了路。看到你的使用，我猜你只想要一个int的数组。如果你这样做然后

event_flags[flag] = i;

到处都没有*，你的问题应该消失。

如果你真的需要那个间接，你不仅需要分配数组event_flags，还需要分配这些指针所指向的所有单个数组，例如

for (size_t j = startvalue; j < something; ++j)
   event_flags[j] = malloc(whatever);

Answer 2

我认为您可能会遇到*运算符与[]运算符的优先级问题。那是*event_flags[flag]而(*event_flags)[flag]不引用相同的内存位置。第一个对应**(event_flags + flag)（可能无法访问），而第二个对应*((*event_flags) + flag)（你想要的）。

因此，您应该将代码重写为：

int** event_flags;
// ...
*event_flags = realloc(*event_flags, sizeof(int) * (flag + 1));
(*event_flags)[flag] = i;

循环不会超过8？

2 个答案: