struct DIR的前向声明

forward declaration of struct DIR

本文关键字：声明 DIR struct      更新时间：2023-10-16

我把include弄乱了，但没能找到错误:

#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <errno.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef DEBUG
#define DLOG(x) printf(x)
#define PLOG(x,y) printf(x,y)
#else
#define DLOG(x)
#define PLOG(x,y)
#endif
harddrive::Results* harddrive::search_for(char* start,char* target,char** ignore,int size) {
PLOG("work directory: %s",start);
DIR* curr_dir = opendir(start);
Results* local = new Results;
if(!curr_dir) {
    printf(" opendir() failure, probably no real directory: %s",start);
    errno = 0;
    return NULL;
}
struct dirent* elem;
while( (elem = readdir(curr_dir)) ) {
    //form URI
    char* uri = form_uri(start,curr_dir->d_name); //here is the actual error
    struct stat st;
    lstat(elem->d_name,&st);
    if( S_ISDIR(st.st_mode) ) {
        if( !do_ignore(uri,ignore,size) )
            local = merge(local,search_for( form_uri(start,elem->d_name), target,ignore,size));
    } 
    else if( S_ISREG(st.st_mode) ) { //this is line 41
编译器输出:

Directory.cpp: In function ‘harddrive::Results* harddrive::search_for(char*, char*, char**, int)’:
Directory.cpp:34:38: error: invalid use of incomplete type ‘struct DIR’
/usr/include/dirent.h:128:16: error: forward declaration of ‘struct DIR’

curr_dir->d_name应为elem->d_name。

如错误所示，您错误地试图解引用指向不透明类型DIR的指针。

DIR*是一个不透明句柄，你不能访问它的内部。您可能想访问elem而不是curr_dir

。把

form_uri(start,curr_dir->d_name);


form_uri(start,elem->d_name);

dirent.h says:
/* This is the data type of directory stream objects.
   The actual structure is opaque to users.  */
typedef struct __dirstream DIR;
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