C malloc分段错误

Question

In the function RenameSubs() when I try debugging I get segmentation fault at this line of code

subsdir[i] = (char*)malloc((GetStringSize(moviesdir[i]) + 1 + 4) * sizeof(char));

I don't understand why — can you explain?

int main()
{
    int number;
    char *mainDirectory = NULL,**names = NULL;

    printf("Give the movies directory: ");
    mainDirectory = ReadMainDirectory();

    if(GetFiles(&mainDirectory,&names,&number) != 0)
    {
        RenameSubs(number,mainDirectory,names);
        system("PAUSE");
        return 1;
    }

    system("PAUSE");
    return 0;
}

char* ReadMainDirectory()
{
    char *dir,c;
    int size = 1;

    dir = (char*)malloc(size+1);
    dir[size-1] = '\0';

    while((c = getchar()) != '\n')
    {
        dir[size-1] = c;
        size++;

        dir = (char*)realloc(dir,size+1);
        dir[size-1] = '\0';
    }

    return dir;
}

int GetFiles(char **dir,char ***names,int *number)
{
    struct dirent *dp;
    DIR *fd;

    if ((fd = opendir(*dir)) == NULL)
    {
        printf("Can't open directory %s!\n",*dir);
        return 0;
    }

    *number = 0;

    *names = (char**)malloc(((*number)+1) * sizeof(char*));

    while ((dp = readdir(fd)) != NULL)
    {
        if (!strcmp(dp->d_name, ".") || !strcmp(dp->d_name, ".."))
        {
            continue;
        }

        (*names)[*number] = strdup(dp->d_name);

        (*number)++;

        *names = (char**)realloc(*names,((*number)+1) * sizeof(char*));
    }

    closedir(fd);

    return 1;
}

int GetStringSize(char *string)
{
    int size = 0;

    while(string[size] != '\0')
    {
        size++;
    }

    return size;
}

int StringEndsWith(char* string,char* extension)
{
    int size;
    char *strextension = NULL;

    size = GetStringSize(string);

    strextension = (char*)malloc(5 * sizeof(char));

    strextension[0] = string[size-4];
    strextension[1] = string[size-3];
    strextension[2] = string[size-2];
    strextension[3] = string[size-1];
    strextension[4] = '\0';

    if(strcmp(strextension,extension) == 0)
    {
        return 1;
    }

    return 0;
}

void RenameSubs(int number,char* mainDir,char** filenames)
{
    int i,mainDirSize,movieDirSize[number],moviesdirnumber,subsdirnumber,j,y;
    char **moviesdir = NULL,**subsdir = NULL,**subsdest = NULL,**moviesdirfilenames = NULL,**subsdirfilenames = NULL,*moviesname = NULL;

    moviesdir = (char**)malloc(number * sizeof(char*));

    mainDirSize = GetStringSize(mainDir);

    for(i=0;i<number;i++)
    {
        movieDirSize[i] = mainDirSize + 1 + GetStringSize(filenames[i]);

        moviesdir[i] = (char*)malloc((movieDirSize[i]+1) * sizeof(char));

        strcpy(moviesdir[i],mainDir);
        strcat(moviesdir[i],"\\");
        strcat(moviesdir[i],filenames[i]);

        GetFiles(&moviesdir[i],&moviesdirfilenames,&moviesdirnumber);

        subsdir[i] = (char*)malloc((GetStringSize(moviesdir[i]) + 1 + 4) * sizeof(char));

        strcpy(subsdir[i],moviesdir[i]);
        strcat(subsdir[i],"\\");
        strcat(subsdir[i],"Subs");

        GetFiles(&subsdir[i],&subsdirfilenames,&subsdirnumber);

        subsdest[i] = (char*)malloc((GetStringSize(subsdir[i]) + GetStringSize(subsdirfilenames[0]) + 1) * sizeof(char));

        strcpy(subsdest[i],subsdir[i]);
        strcat(subsdest[i],"\\");
        strcat(subsdest[i],subsdirfilenames[0]);

        for(j=0;j<moviesdirnumber;j++)
        {
            if(StringEndsWith(moviesdirfilenames[j],".mkv") || StringEndsWith(moviesdirfilenames[j],".mp4") || StringEndsWith(moviesdirfilenames[j],".avi"))
            {
                moviesname = (char*)malloc((GetStringSize(moviesdirfilenames[j]) - 4 + 1) * sizeof(char));

                for(y=0;y<(GetStringSize(moviesdirfilenames[j]) - 4);y++)
                {
                    moviesname[y] = moviesdirfilenames[j][y];
                }

                moviesname[y] = '\0';

                break;
            }
        }
    }
}

Answer 1

You are using array of pointers without initializing it first . initialize it.

In loop

 subsdir[i] = malloc((GetStringSize(moviesdir[i]) + 1 + 4) * sizeof(char));

This is the second step . First u need to initialize

 subsdir = malloc (sizeof(char*) * number);