C在结构中初始化数组 [英] C initialize array within structure

问题描述

我想在结构中包含一个可变长度的数组，但无法正确初始化它.

I want to have an variable-length array contained within a structure, but am having trouble initializing it correctly.

struct Grid {
  int rows;
  int cols;
  int grid[];
}

int main() {
  struct Grid testgrid = {1, 3, {4, 5, 6}};
}

我尝试的一切都给我一个错误:灵活数组成员的非静态初始化"错误.

Everything I try gives me an 'error: non-static initialization of a flexible array member' error.

推荐答案

您可以通过将结构设为 static 或全局来使其在 gcc 中工作，但事实证明，初始化灵活的数组成员是不符合标准，因此除了 gcc 外，它可能无法正常工作.这是一种仅使用符合 C99 的功能的方法...

You can make that work in gcc by making the struct either static or global, but it turns out that initializing flexible array members is non-conforming and so it is likely to not work except with gcc. Here is a way to do it that just uses C99-conforming features...

#include <stdlib.h>
#include <stdarg.h>

typedef struct Grid {
  int rows;
  int cols;
  int grid[];
} *Grid;

Grid newGrid(int, int, ...);

Grid newGrid(int rows, int cols, ...)
{
Grid g;
va_list ap;
int i, n = rows * cols;

  if((g = malloc(sizeof(struct Grid) + rows * cols * sizeof(int))) == NULL)
    return NULL;
  g->rows = rows;
  g->cols = cols;
  va_start(ap, cols);
  for(i = 0; i < n; ++i)
    g->grid[i] = va_arg(ap, int);
  va_end(ap);
  return g;
}
.
.
.
Grid g1, g2, g3;
g1 = newGrid(1, 1, 123);
g2 = newGrid(2, 3, 1, 1, 1,
                   2, 2, 2);
g3 = newGrid(4, 5, 1,  2,  3,  4,  5,
                   6,  7,  8,  9, 10,
                  11, 12, 13, 14, 15,
                  16, 17, 18, 19, 20);

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