c - 错误 : request for member xxxxxx in something not a structure or union

Question

这是一个旨在处理 ppm 图像文件的程序。

当我尝试使用接受全局结构变量的函数并提取该图像的成员时，出现编译错误。

这是全局结构(在 ppmIO.c 和 ppmIO.h 中声明):

ppmIO.c:

struct Image *instance;

ppmIO.h:

struct Image
{
  int width;
  int height;
  unsigned char *data;
};

extern struct Image *instance;

这是我从 main 调用函数的方式:

  ImageInvert(&instance);

这些是我的 imageManip.c 文件的相关部分:

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <ppmIO.h>
#include <imageManip.h>

void ImageInvert(struct Image **toInvert) {


  int i;
  int pix = (*toInvert->width) * (*toInvert->height);

  for (i = 0; i < pix; i++)
    {
      *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data));
      *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
      *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
    }

}

这是我的 imageManip.h 文件:

#include <ppmIO.h>

void ImageInvert(struct Image **toInvert);

void ImageSwap(struct Image **toSwap);

这些是我得到的错误:

imageManip.c:31:23: error: request for member ‘width’ in something not a structure or union
   int pix = (*toInvert->width) * (*toInvert->height);
                       ^
imageManip.c:31:44: error: request for member ‘height’ in something not a structure or union
   int pix = (*toInvert->width) * (*toInvert->height);
                                            ^
imageManip.c:35:18: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data));
                  ^
imageManip.c:35:60: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data));
                                                            ^
imageManip.c:35:67: error: expected ‘;’ before ‘)’ token
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data));
                                                                   ^
imageManip.c:35:67: error: expected statement before ‘)’ token
imageManip.c:36:18: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
                  ^
imageManip.c:36:60: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
                                                            ^
imageManip.c:36:69: error: expected ‘;’ before ‘)’ token
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
                                                                     ^
imageManip.c:36:69: error: expected statement before ‘)’ token
imageManip.c:37:18: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
                  ^
imageManip.c:37:60: error: request for member ‘data’ in something not a structure or union
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));
                                                            ^
imageManip.c:37:69: error: expected ‘;’ before ‘)’ token
       *(toInvert)->data = ((unsigned char)255 - *(toInvert)->data++));

不确定我是否正确访问了成员或者是否正确使用了指针...

Answer 1

我使用括号的方式存在问题。

这是 imageInvert 函数的工作版本:

void ImageInvert(struct Image **toInvert) {


  int i;
  int pix = (*toInvert)->width * (*toInvert)->height;

  for (i = 0; i < pix; i++)
    {
      (*toInvert)->data = ((unsigned char)255 - (unsigned char)(*toInvert)->data);
      (*toInvert)->data = ((unsigned char)255 - (unsigned char)(*toInvert)->data++);
      (*toInvert)->data = ((unsigned char)255 - (unsigned char)(*toInvert)->data++);
    }

}