Ç复合文字，指针数组 [英] C compound literals, pointer to arrays

问题描述

我试图复合字面常量分配给一个变​​量，但它似乎不工作，请参阅：

I'm trying to assign a compound literal to a variable, but it seems not to work, see:

  int *p[] = (int *[]) {{1,2,3},{4,5,6}};

我在GCC一个错误。

I got a error in gcc.

但如果我只写这样的：

  int p[] = (int []) {1,2,3,4,5,6};

然后，它没关系。

Then it's okay.

不过，是不是我想要的。

But is not what I want.

我不明白，为什么出现错误;因为如果我初始化它像一个阵列，或字符数组的指针使用它，它的好，见：

I don't understand why the error occurrs, because if I initialize it like a array, or use it with a pointer of arrays of chars, its okay, see:

  int *p[] = (int *[]) {{1,2,3},{4,5,6}}; //I got a error
  int p[][3] = {{1,2,3},{4,5,6}}; //it's okay
  char *p[] = (char *[]) {"one", "two"...}; // it's okay!

请注意，我不明白为什么我得到了第一个错误，并请我不能，否则我不想写这样的第二种形式，因为它需要一个复合文字，和我不不想说有多大阵列编译器。我想是这样，第二个，但对于int值。

Note I don't understand why I got an error in the first one, and please I can't, or I don't want to write like the second form because it's needs to be a compound literals, and I don't want to say how big is the array to the compiler. I want something like the second one, but for int values.

先谢谢了。

推荐答案

首先，铸件在所有的例子多余的，可以删除。其次，您使用的初始化多维数组的语法，这需要以分配的内存连续块的定义的第二个维度。相反，请尝试以下两种方法之一：

First, the casts are redundant in all of your examples and can be removed. Secondly, you are using the syntax for initializing a multidimensional array, and that requires the second dimension the be defined in order to allocate a sequential block of memory. Instead, try one of the two approaches below:

• 多维数组：

• Multidimensional array:

int p[][3] = {{1,2,3},{4,5,6}};

指针数组一维数组：

Array of pointers to one dimensional arrays:

int p1[] = {1,2,3};
int p2[] = {4,5,6};
int *p[] = {p1,p2};

后一种方法具有允许用于改变长度的子阵列的优点。然而，前一种方法可以确保内存连续布局。

The latter method has the advantage of allowing for sub-arrays of varying length. Whereas, the former method ensures that the memory is laid out contiguously.

这是我强烈建议您不要使用另一种方法是EN code在字符串中的整数。这是一个不可移植的黑客。另外，在字符串中的数据被认为是恒定的。做你的阵列需要是可变的？

Another approach that I highly recommend that you do NOT use is to encode the integers in string literals. This is a non-portable hack. Also, the data in string literals is supposed to be constant. Do your arrays need to be mutable?

int *p[] = (int *[]) {
    "\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00",
    "\x04\x00\x00\x00\x05\x00\x00\x00\x06\x00\x00\x00"
};

这例子可能是32位小端机器上工作，但我从一个iPad打字这一点，目前无法核实。再次，请不要使用;我甚至把它觉得脏。

That example might work on a 32-bit little-endian machine, but I'm typing this from an iPad and cannot verify it at the moment. Again, please don't use that; I feel dirty for even bringing it up.

在发现的铸造方法也出现的指针的指针运行。这可以被索引像多维数组也是如此。

The casting method you discovered also appears to work with a pointer to a pointer. That can be indexed like a multidimensional array as well.

int **p = (int *[]) { (int[]) {1,2,3}, (int[]) {4,5,6} };

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