GCC:数组类型具有不完整的元素类型 [英] GCC: Array type has incomplete element type

问题描述

我已经声明了一个 struct，并且我尝试将这些结构的数组(以及一个双精度数组和一个整数的 double 数组)传递给一个函数.我在编译时从 gcc 收到 数组类型具有不完整的元素类型" 消息.将 struct 传递给函数的方式有什么问题?

typedef struct graph_node {整数 X;输入 Y;活动；} g_node;void print_graph(g_node graph_node[], double weight[][], int nodes);

我也尝试过 struct g_node graph_node[]，但我得到了同样的结果.

解决方案

导致问题的数组:

void print_graph(g_node graph_node[], double weight[][], int nodes);

必须给出第二个和后续维度:

void print_graph(g_node graph_node[], double weight[][32], int nodes);

或者你可以只给出一个指向指针的指针:

void print_graph(g_node graph_node[], double **weight, int nodes);

然而，尽管它们看起来相似，但它们的内部却大不相同.

如果您使用的是 C99，则可以使用可变限定数组.引用 C99 标准中的一个例子(第 6.7.5.2 节数组声明符):

void fvla(int m, int C[m][m]);//有效:具有原型作用域的 VLAvoid fvla(int m, int C[m][m])//有效:调整为自动指向 VLA{typedef int VLA[m][m];//有效:块作用域 typedef VLA结构标签{int (*y)[n];//无效:y 不是普通标识符int z[n];//无效:z 不是普通标识符};int D[m];//有效:自动 VLA静态整数 E[m];//无效:静态块作用域 VLAextern int F[m];//无效:F 有链接并且是 VLAint (*s)[m];//有效:自动指向 VLAextern int (*r)[m];//无效:r 有链接并指向 VLAstatic int (*q)[m] = &B;//有效:q 是指向 VLA 的静态块指针}

<小时>

评论中的问题

<块引用>

[...] 在我的 main() 中，我试图传递给函数的变量是一个 double array[][]，那么我该如何将它传递给函数呢?将 array[0][0] 传入它给了我不兼容的参数类型，&array 和 &array[0][0].

在你的 main() 中，变量应该是:

双数组[10][20];

或类似的东西；也许

double array[][20] = { { 1.0, 0.0, ... }, ... };

你应该可以用这样的代码传递它:

typedef struct graph_node{整数 X;输入 Y;活动；} g_node;void print_graph(g_node graph_node[], double weight[][20], int nodes);int main(void){g_node g[10];双数组[10][20];整数 n = 10;打印图(g，数组，n)；返回0；}

使用 GCC 4.2(i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1(基于 Apple Inc. build 5658)(LLVM build 2336.9.00))和还使用命令行在 Mac OS X 10.7.3 上使用 GCC 4.7.0:

/usr/bin/gcc -O3 -g -std=c99 -Wall -Wextra -c zzz.c

I have declared a struct, and I try to pass an array of those structs (as well as a double array of doubles, and an integer) into a function. I get an "array type has incomplete element type" message from gcc when I compile it. What have I gotten wrong in how I pass the struct to the function?

typedef struct graph_node {
  int X;
  int Y;
  int active;
} g_node;

void print_graph(g_node graph_node[], double weight[][], int nodes);

I have also tried struct g_node graph_node[], but I get the same thing.

解决方案

It's the array that's causing trouble in:

void print_graph(g_node graph_node[], double weight[][], int nodes);

The second and subsequent dimensions must be given:

void print_graph(g_node graph_node[], double weight[][32], int nodes);

Or you can just give a pointer to pointer:

void print_graph(g_node graph_node[], double **weight, int nodes);

However, although they look similar, those are very different internally.

If you're using C99, you can use variably-qualified arrays. Quoting an example from the C99 standard (section §6.7.5.2 Array Declarators):

void fvla(int m, int C[m][m]); // valid: VLA with prototype scope

void fvla(int m, int C[m][m])  // valid: adjusted to auto pointer to VLA
{
    typedef int VLA[m][m];     // valid: block scope typedef VLA
    struct tag {
        int (*y)[n];           // invalid: y not ordinary identifier
        int z[n];              // invalid: z not ordinary identifier
    };
    int D[m];                  // valid: auto VLA
    static int E[m];           // invalid: static block scope VLA
    extern int F[m];           // invalid: F has linkage and is VLA
    int (*s)[m];               // valid: auto pointer to VLA
    extern int (*r)[m];        // invalid: r has linkage and points to VLA
    static int (*q)[m] = &B;   // valid: q is a static block pointer to VLA
}

---

Question in comments

[...] In my main(), the variable I am trying to pass into the function is a double array[][], so how would I pass that into the function? Passing array[0][0] into it gives me incompatible argument type, as does &array and &array[0][0].

In your main(), the variable should be:

double array[10][20];

or something faintly similar; maybe

double array[][20] = { { 1.0, 0.0, ... }, ... };

You should be able to pass that with code like this:

typedef struct graph_node
{
    int X;
    int Y;
    int active;
} g_node;

void print_graph(g_node graph_node[], double weight[][20], int nodes);

int main(void)
{
    g_node g[10];
    double array[10][20];
    int n = 10;

    print_graph(g, array, n);
    return 0;
}

That compiles (to object code) cleanly with GCC 4.2 (i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.9.00)) and also with GCC 4.7.0 on Mac OS X 10.7.3 using the command line:

/usr/bin/gcc -O3 -g -std=c99 -Wall -Wextra -c zzz.c

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