为另一个结构内的结构数组分配内存 [英] Allocating memory for a structure array inside another structure

问题描述

我真的不知道这里有什么问题.编译器说一切正常，但是当我运行它时，可执行文件崩溃了(我相信这是一个分段错误问题).都说两颗心总比一颗好，所以我希望你们能找到我遗漏的东西.

I really don't know what the issue is here. The compiler says it's all okay, but when I run it, the executable crashes ( I believe it's a segmentation fault problem ). They say two minds are always better than one, so I hope you guys can find whatever I have missed.

好的，所以它是这样的:我有两个结构:

Okay, so it goes this way: I have 2 structures:

struct _Color {

    unsigned char r,g,b;
    char *pchars;
}; //typedef to Color in header file

struct _XPM {

    unsigned int width;
    unsigned int height;
    unsigned char cpp; 
    unsigned int ncolors;
    Color *colta; //collor table
    unsigned int *data[];

}; //typedef to XPM in header file

然后，在一个函数中，我为 XPM 结构分配内存，然后为 XPM 结构内的 Color 数组分配内存(我不会在这里编写故障安全代码):

Then, in a function I allocate memory for the XPM structure and then for the Color array inside the XPM structure (I won't write the fail safe code here):

XPM *imagine; //received as a parameter
imagine = ( XPM* ) malloc ( sizeof ( XPM ) + sizeof ( unsigned int* ) * width );
imagine -> colta = malloc ( ncolors * sizeof ( imagine -> colta ) ); 
/*I tried with both *imagine ->colta and imagine -> colta just to be safe */

当我尝试访问颜色表中的字段时出现问题

The problem shows when I try accessing the fields in the Color table

imagine -> colta [ index ].r = r;

也许这只是我犯的一个小错误，但我找不到.有人有想法吗?

Maybe it's just a small mistake I made, but I cannot find it. Does anyone have an idea?

谢谢！:)

编辑

main 函数中到这个程度的代码是这样的:

The code in the main function to this extent is this:

XPM *img;
initXPM(img, 10, 10, 1, 3);
setXPMColor(img, 0, 255, 255, 255, "0");

setXPMColor 函数是这样的:

The setXPMColor function goes like this:

void setXPMColor(XPM *imagine,
    unsigned int index,
    unsigned char r,
    unsigned char g,
    unsigned char b,
    char *charpattern) {


   imagine -> colta [ index ].r = r;
   imagine -> colta [ index ].g = g;
   imagine -> colta [ index ].b = b;
   imagine -> colta [ index ].pchars = charpattern;
}

推荐答案

void func(type *pointer){
    //"type *pointer" : The only variable on the stack
    pointer = malloc(sizeof(type));//But is not set to the original.
    retrurn;
}

简短的测试代码:

#include <stdio.h>
#include <stdlib.h>

void init_int_pointer(int *p){
    p = malloc(sizeof(*p));
}

int main(){
    int *p = NULL;
    printf("before : %p\n", (void*)p);//NULL
    init_int_pointer(p);
    printf("after : %p\n", (void*)p);//NULL

    return 0;
}

修复

1)
type * func(){
    type *pointer = malloc(sizeof(type));
    retrurn pointer;
}
...
type *p = func();

2)
void func(type **pointer){
    *pointer = malloc(sizeof(type));
    retrurn ;
}
...
type *p;
func(&p);

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