指向數組的指針作為函數參數
[英]Pointer to array as function parameter
I wrote a function which takes a pointer to an array to initialize its values:
我寫了一個函數，它接受一個指向數組的指針來初始化它的值：
#define FIXED_SIZE 256
int Foo(int *pArray[FIXED_SIZE])
{
/*...*/
}
//Call:
int array[FIXED_SIZE];
Foo(&array);
And it doesn't compile:
它不編譯：
error C2664: 'Foo' : cannot convert parameter 1 from 'int (*__w64 )[256]' to 'int *[]'
錯誤C2664：'Foo'：無法將參數1從'int（* __ w64）[256]'轉換為'int * []'
However, I hacked this together:
但是，我一起攻擊了這個：
typedef int FixedArray[FIXED_SIZE];
int Foo(FixedArray *pArray)
{
/*...*/
}
//Call:
FixedArray array;
Foo(&array);
And it works. What am I missing in the first definition? I thought the two would be equivalent...
它有效。我在第一個定義中缺少什么？我以為這兩個是等價的......
3 个解决方案
#1
13
int Foo(int *pArray[FIXED_SIZE])
{
/*...*/
}
In the first case, pArray is an array of pointers, not a pointer to an array.
在第一種情況下，pArray是一個指針數組，而不是指向數組的指針。
You need parentheses to use a pointer to an array:
您需要括號來使用指向數組的指針：
int Foo(int (*pArray)[FIXED_SIZE])
You get this for free with the typedef (since it's already a type, the * has a different meaning). Put differently, the typedef sort of comes with its own parentheses.
你可以使用typedef免費獲得這個（因為它已經是一個類型，*具有不同的含義）。換句話說，typedef類型帶有自己的括號。
Note: experience shows that in 99% of the cases where someone uses a pointer to an array, they could and should actually just use a pointer to the first element.
注意：經驗表明，在99％的情況下，有人使用指向數組的指針，他們可以而且實際上應該只使用指向第一個元素的指針。
#2
2
One simple thing is to remember the clockwise-spiral rule which can be found at http://c-faq.com/decl/spiral.anderson.html
一個簡單的事情是記住順時針螺旋規則，可以在http://c-faq.com/decl/spiral.anderson.html找到。
That would evaluate the first one to be an array of pointers . The second is pointer to array of fixed size.
那將評估第一個是一個指針數組。第二個是指向固定大小數組的指針。
#3
0
An array decays to a pointer. So, it works in the second case. While in the first case, the function parameter is an array of pointers but not a pointer to integer pointing to the first element in the sequence.
數組衰減到指針。所以，它適用於第二種情況。在第一種情況下，函數參數是一個指針數組，但不是一個指向序列中第一個元素的整數的指針。
注意！
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