C语言 C 错误数组：数组类型具有不完整的元素类型。
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C error Array: array type has incomplete element type.
提问by ambika
I have:
我有：
extern int docx(char *,char[][]) // in a header file
It is compiled properly in solaris, but in Redhat Linux it shows the error bellow:
它在 solaris 中正确编译，但在 Redhat Linux 中显示以下错误：
array type has incomplete element type.
I know i can solve it as - char[][20]
我知道我可以解决它 - char[][20]
Is it the right way?
这是正确的方法吗？
回答by David Rodríguez - dribeas
You will have to know what the function is actually expecting and modify the interface accordingly. If it is expecting a bidimensional array (char [N][M]) the correct interface would be:
您必须知道该函数实际期望什么并相应地修改接口。如果它需要一个二维数组 ( char [N][M])，则正确的接口将是：
extern int docx(char *,char*[M]);
Which is different from:
与以下不同：
extern int docx( char*, char** );
In the first case the function would be expecting a pointer into a contiguous block of memory that holds N*Mcharacters (&p[0][0]+M == &p[1][0]and (void*)&p[0][0]==(void*)&p[0]), while in the second case it will be expecting a pointer into a block of memory that holds Npointers to blocks of memory that may or not be contiguous (&p[0][0]and &p[1][0]are unrelated and p[0]==&p[0][0])
在第一种情况下，该函数将期望一个指向包含N*M字符 ( &p[0][0]+M == &p[1][0]and (void*)&p[0][0]==(void*)&p[0])的连续内存块的指针，而在第二种情况下，它将期望一个指向内存块的N指针，该内存块包含指向内存块的指针，这些内存块可能或不连续（&p[0][0]并且&p[1][0]不相关并且p[0]==&p[0][0]）
// case 1
ptr ------> [0123456789...M][0123.........M]...[0123.........M]
// case 2
ptr ------> 0 [ptr] -------> "abcde"
1 [ptr] -------> "another string"
...
N [ptr] -------> "last string"
回答by slartibartfast
char *[M]is no different from char **. char *[M]is an array of pointers to char. The dimension plays no role in C (in this case). What David meant was char (*)[M]which is a pointer to an array of M chars which would be the correct type for your prototype - but your char [][M]is fine also (in fact it is the more common formulation).
char *[M]与 没有什么不同char **。char *[M]是一个指向 char 的指针数组。维度在 C 中不起作用（在这种情况下）。David 的意思是char (*)[M]这是一个指向 M 个字符数组的指针，它是您的原型的正确类型 - 但您的char [][M]也很好（实际上它是更常见的公式）。
