C语言 为什么即使在 C 中分配给一个大的可变长度数组也有一个固定值 -1？
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Why does a large variable length array has a fixed value -1 even if assigned to in C?
提问by dubbeat
I'm trying to make a variable sized array in c.
我正在尝试在 c 中创建一个可变大小的数组。
The array keeps on coming back as having a value of -1.
数组不断返回，值为 -1。
What I want to do is to make an array of size sizeand then incrementally add values to it. What am I doing wrong?
我想要做的是制作一个大小的数组，size然后逐步向其中添加值。我究竟做错了什么？
int size = 4546548;
UInt32 ar[size];
//soundStructArray[audioFile].audioData = (UInt32 *)malloc(sizeof(UInt32) * totalFramesInFile);
//ar=(UInt32 *)malloc(sizeof(UInt32) * totalFramesInFile);
for (int b = 0; b < size; b++)
{
UInt32 l = soundStructArray[audioFile].audioDataLeft[b];
UInt32 r = soundStructArray[audioFile].audioDataRight[b];
UInt32 t = l+r;
ar[b] = t;
}
采纳答案by jer
What you need is a dynamic array. One that you can allocate an initial size, then use reallocto increase the size of it by some factor when appropriate.
你需要的是一个动态数组。您可以分配一个初始大小，然后realloc在适当的时候使用某个因素来增加它的大小。
I.e.,
IE，
UInt32* ar = malloc(sizeof(*ar) * totalFramesInFile);
/* Do your stuff here that uses it. Be sure to check if you have enough space
to add to ar and if not, call grow_ar_to() defined below. */
Use this function to grow it:
使用这个函数来增长它：
UInt32* grow_ar_to(UInt32* ar, size_t new_bytes)
{
UInt32* tmp = realloc(ar, new_bytes);
if(tmp != NULL)
{
ar = tmp;
return ar;
}
else
{
/* Do something with the error. */
}
}
回答by Wyatt Anderson
You should probably allocate (and subsequently free) the array dynamically, like so:
您可能应该动态分配（并随后释放）数组，如下所示：
int *ar = malloc(sizeof(int) * size);
for (int b = 0; b < size; b++)
{
...
}
// do something with ar
free(ar);
回答by Hervé
if you make size a const int that should work. Also, if your array is inside a function and size is an argument of said function, that should work too.
如果你让 size 成为一个应该工作的 const int 。此外，如果您的数组在一个函数内并且 size 是所述函数的参数，那也应该有效。
回答by Argote
C does not allow a variable to be used when defining an array size, what you'd need to do is use malloc, this should give you an idea:
C 不允许在定义数组大小时使用变量，您需要做的是使用malloc，这应该给您一个想法：
UInt32* ar;
ar = (UInt32*) malloc(size * sizeof(UInt32));
Don't forget to free it up afterwards
之后不要忘记释放它
