[英]How can I store a variable length array in a struct in C
I want to store a variable length array in a struct, and I use a pointer for this purpose. 我想在结构中存储一个可变长度的数组,为此我使用了一个指针。 However, if I retrieve the stored array, I get the wrong values back.
但是,如果检索存储的数组,则会返回错误的值。 In the example below, I get the output "1 0", while you would expect the output "1 2".
在下面的示例中,我得到输出“ 1 0”,而您期望输出“ 1 2”。
#include <stdio.h>
typedef struct Flexibility {
int *flex;
} Flexibility;
Flexibility calculateFlexibility()
{
int a[2];
a[0] = 1;
a[1] = 2;
Flexibility f;
f.flex = a;
return f;
}
void main()
{
Flexibility f;
f = calculateFlexibility();
int i;
for(i = 0; i < 2; i++)
{
fprintf(stdout, "%i ", *(f.flex + i));
}
}
you're creating temporary variable a
in function calculateFlexibility
, then you store pointer to f.flex
variable, but after function is ended - a
is gone from memory, so your f.flex
pointer is now pointing to nowhere 要创建临时变量
a
函数calculateFlexibility
,那么你存储指针f.flex
变量,但功能结束之后- a
是从内存中消失了,所以你f.flex
指针正指向无处
if you want to have really variable length, you should do something like this: 如果您想要真正可变的长度,则应执行以下操作:
Flexibility calculateFlexibility()
{
Flexibility f;
f.flex = (int*)malloc(....);
return f;
}
and at the end of program: 并在程序结束时:
free(f.flex);
for proper arguments of malloc I suggest you to read: http://en.cppreference.com/w/c/memory/malloc 有关malloc的正确参数,建议您阅读: http : //en.cppreference.com/w/c/memory/malloc
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