如何在C中初始化一个指针结构的二维数组为空?

I have the following struct:

我有以下结构:

typedef void (*HSM_State_Fcn)(void*, size_t);
typedef HSM_State_Fcn HSM_Dest_State_Fcn;
typedef uint8_t (*HSM_Guard_Fcn)(void*, size_t);
typedef void (*HSM_Action_Fcn)(void*, size_t);

typedef struct HSM_Transition_Tag
{
    HSM_Dest_State_Fcn dest_fcn;
    HSM_Guard_Fcn      guard_fcn;
    HSM_Action_Fcn     action_fcn;
}HSM_Transition_T;

And I have the following 2D array that I want every element to be NULL:

我有下面的2D数组我想让每个元素都是空的:

static HSM_Transition_T Transition_Table_Array_Test[3][3] = {NULL};

As you can see I tried to equal to {NULL} but I get the following warning:

如您所见，我试图等于{NULL}，但我得到以下警告:

warning: (near initialization for 'Transition_Table_Array_Test[0]') [-Wmissing-braces]

警告:(对“Transition_Table_Array_Test[0]”进行近初始化)

What would be the correct approach to initialize every element to NULL?

将每个元素初始化为NULL的正确方法是什么?

If I make it:

如果我让它:

static HSM_Transition_T Transition_Table_Array_Test[3][3] = {{NULL}};

I get the same error.

我得到了同样的错误。

3 个解决方案

#1

static HSM_Transition_T* Transition_Table_Array_Test[3][3]={{NULL}};

NULL should be used with pointers not structure.

NULL应该用于指针而不是结构。

If you want to initialize struct fields in 2d array of structs, then

如果要在结构体的2d数组中初始化结构体字段，则

static HSM_Transition_T Transition_Table_Array_Test[3][3]={{{NULL,NULL,NULL}}};

#2

The reason you're getting a warning is because NULL is a primitive, but the elements of your array are aggregates; they need to either be initialized with an aggregate variable (of the right type), or with yet a third braced expression (constructing an aggregate in-place).

得到警告的原因是NULL是一个原语，但是数组的元素是聚合的;它们需要使用聚合变量(正确的类型)初始化，或者使用第三个支撑表达式(在适当的位置构造聚合)初始化。

The type of the array does not admit using NULL to initialize the elements, because structure values cannot be NULL, only pointers. Structures exist in-place, so it's not possible for them to be "absent" from the array (the elements of the array are the structures; if the array exists, so do they).

数组的类型不允许使用NULL来初始化元素，因为结构值不能为NULL，只能是指针。结构存在于适当的位置，所以它们不可能从数组中“缺席”(数组的元素是结构;如果数组存在，那么它们也存在)。

The compiler is complaining that braces are still missing, rather than telling you a structure value cannot be NULL, because it thinks you're trying to initialize the function pointers within the HSM_Transition_T to NULL (which is an operation that would make sense).

编译器在抱怨大括号仍然丢失，而不是告诉您结构值不能为NULL，因为它认为您正在尝试将HSM_Transition_T中的函数指针初始化为NULL(这是一个有意义的操作)。

#3

You can write:

你可以写:

static HSM_Transition_T Transition_Table_Array_Test[3][3] = {
    {NULL, NULL, NULL},
    {NULL, NULL, NULL},
    {NULL, NULL, NULL}};

But NULL is mostly used with pointer and not struct.

但是NULL主要用于指针，而不是struct。

You would have written (note the '*' before Transition_Table_Array_Test:

您应该已经编写(请注意Transition_Table_Array_Test之前的“*”:

static HSM_Transition_T *Transition_Table_Array_Test[3][3] = {
    {NULL, NULL, NULL},
    {NULL, NULL, NULL},
    {NULL, NULL, NULL}};

#1

static HSM_Transition_T* Transition_Table_Array_Test[3][3]={{NULL}};