C:常量结构数组中的外部常量int

当使用外部常量整数初始化结构数组时，我收到一条错误消息“表达式必须具有常量值”

File1.c:

const unsigned char data1[] =
{
    0x65, 0xF0, 0xA8, 0x5F, 0x5F,
    0x5F, 0x5F, 0x31, 0x32, 0x2E,
    0x31, 0xF1, 0x63, 0x4D, 0x43, 
    0x52, 0x45, 0x41, 0x54, 0x45,
    0x44, 0x20, 0x42, 0x59, 0x3A,
    0x20, 0x69, 0x73, 0x70, 0x56, 
// ...
};
const unsigned int data1_size = sizeof(data1);

const unsigned char data2[] =
{
    0x20, 0x44, 0x61, 0x74, 0x61,
    0x20, 0x52, 0x6F, 0x77, 0x20,
    0x3D, 0x20, 0x34, 0x38, 0x12, 
//...
};
const unsigned int data2_size = sizeof(data2);

extern const unsigned char * data1;
extern const unsigned int    data1_size;
extern const unsigned char * data2;
extern const unsigned int    data2_size;

struct Array_Attributes
{
    const unsigned char *    p_data;
    const unsigned int       size;
};

const struct Array_Attributes Data_Arrays[] =
{
    {data1, data1_size},  // Error message is for data1_size here.
    {data2, data2_size},  // Another error message generated for data2_size here.
};

File2.c:

const unsigned char data1[] =
{
    0x65, 0xF0, 0xA8, 0x5F, 0x5F,
    0x5F, 0x5F, 0x31, 0x32, 0x2E,
    0x31, 0xF1, 0x63, 0x4D, 0x43, 
    0x52, 0x45, 0x41, 0x54, 0x45,
    0x44, 0x20, 0x42, 0x59, 0x3A,
    0x20, 0x69, 0x73, 0x70, 0x56, 
// ...
};
const unsigned int data1_size = sizeof(data1);

const unsigned char data2[] =
{
    0x20, 0x44, 0x61, 0x74, 0x61,
    0x20, 0x52, 0x6F, 0x77, 0x20,
    0x3D, 0x20, 0x34, 0x38, 0x12, 
//...
};
const unsigned int data2_size = sizeof(data2);

extern const unsigned char * data1;
extern const unsigned int    data1_size;
extern const unsigned char * data2;
extern const unsigned int    data2_size;

struct Array_Attributes
{
    const unsigned char *    p_data;
    const unsigned int       size;
};

const struct Array_Attributes Data_Arrays[] =
{
    {data1, data1_size},  // Error message is for data1_size here.
    {data2, data2_size},  // Another error message generated for data2_size here.
};

获取字节。c:

const unsigned char data1[] =
{
    0x65, 0xF0, 0xA8, 0x5F, 0x5F,
    0x5F, 0x5F, 0x31, 0x32, 0x2E,
    0x31, 0xF1, 0x63, 0x4D, 0x43, 
    0x52, 0x45, 0x41, 0x54, 0x45,
    0x44, 0x20, 0x42, 0x59, 0x3A,
    0x20, 0x69, 0x73, 0x70, 0x56, 
// ...
};
const unsigned int data1_size = sizeof(data1);

const unsigned char data2[] =
{
    0x20, 0x44, 0x61, 0x74, 0x61,
    0x20, 0x52, 0x6F, 0x77, 0x20,
    0x3D, 0x20, 0x34, 0x38, 0x12, 
//...
};
const unsigned int data2_size = sizeof(data2);

extern const unsigned char * data1;
extern const unsigned int    data1_size;
extern const unsigned char * data2;
extern const unsigned int    data2_size;

struct Array_Attributes
{
    const unsigned char *    p_data;
    const unsigned int       size;
};

const struct Array_Attributes Data_Arrays[] =
{
    {data1, data1_size},  // Error message is for data1_size here.
    {data2, data2_size},  // Another error message generated for data2_size here.
};

我还从

Array\u Attributes

的

size

字段中删除了

const

限定符，并得到了相同的错误消息

当

data1\u size

和

data2\u size

是

const unsigned int

但在不同的转换单元中时，为什么编译器会抱怨常量值表达式

我想要一个在编译时生成的[array address，array size]常量数组

---

我使用的是Green Health CCAM< <代码> 4.24，在WindowsXP上，C语言<强> > > > > C++ > .< P> C >代码> const 限定符与编译器认为的代码<常数表达式< /代码>无关。在初始值设定项中，即

const struct attributes attrs[] = {
    { expr1, expr2 }, 
    ...
}

expr1

和

expr2

必须具有编译器可以接受的非常特定的形式。这些限制的结果是，表达式可以在不从程序变量获取的情况下进行求值，因为这些变量在编译时不存在

您正在尝试使用

data1\u size

和

data2\u size

，根据这些规则，它们不是编译时常量

顺便说一下，声明

const unsigned char data1[] = { ... };

及

不兼容，将导致代码中出现错误。后者应该是

extern const unsigned char data1[];

---

我的理解是

data1[]

和

*data1

是相同的。它们有什么不同，为什么会导致错误？它们唯一可以被替换的地方是在参数声明中

extern char*foo

告诉编译器

foo

是一个包含字符指针的4字节变量

extern char bar[]

告诉编译器

bar

是一个地址常量，指向未知大小的字符块

foo[i]

首先获取4字节指针，添加

i

，然后取消引用以获取字符

bar[i]

获取值

bar

，添加

i

，并取消引用。