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GCC gives me an "array type has incomplete element type"-error message when i try to compile this:
typedef struct _
struct _node{
node (*children)[2];
In memory the struct should look like this
0x pointer to 1. child node
0x pointer to 2. child node
That's because the C type expression works the other way round.
node (*children)[2];
reads as the following: the contents of children, when dereferenced (* is applied to them), yield something on which the array operator [] can be applied, yielding a node. Which means that children is a pointer to an array of two node. However, you do not want a pointer to an array, you want an array of two pointers. For that, you should put the parentheses thus:
node *(children[2]);
which then reads as: the contents of children are an applying * on one of them yields a node. This is what you want: an array of two pointers to node. Note that this is equivalent to:
node *children[2];
because in the C syntax, when it comes to type expressions, the [] operator takes precedence over the * operator.
In your initial version, the C compiler grumbles because at the time it reads the declaration, it does not know what size node is (the structure definition is not complete yet), and, as such, has trouble imagining a type "array of two node". This is a rather indirect symptom of the problem.
Side note: you should refrain from using _node or any other identifier beginning with an underscore in your code. These identifiers are reserved for "the implementation". In practice, system headers may use them, and collisions could prove harmful. Personally, I tend to add the underscore at the end, like this: typedef struct node_
49.6k888145
Instead of this:
node (*children)[2];
struct _node* children[2];
28.4k1176130
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array type has incomplete element type
我在移植代码到hp(ia64 B.11.23)时编译出错，
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我在移植代码到hp(ia64 B.11.23)时编译出错，
编译器用的是gcc4.1.0，错误提示为：
In file included from /usr/include/sys/mp.h:53,
from /usr/include/sys/malloc.h:59,
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incomplete sype
可以看到string的定义，
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dereferencing pointer to incomplete type
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我反复检查了代码，是没有错的。
在网上简单搜了一下，说是头文件包含的问题。
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[问题点数：40分，结帖人mcmay]
关于一个函数指针数组（error: array type has incomplete element type）
[问题点数：40分，结帖人mcmay]
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