CS50的pset4上的分割錯誤

Question

我開始瘋狂地試圖弄清楚我的代碼正在發生什麼。

我目前在CS50的pset4中。恢復挑戰。

對於那些不知道它是什麼的人： 給我們一個名爲card.raw的文件，其中有一些刪除的照片。我們的任務是實施一個程序，可以做一些取證（田園詩般的），並恢復丟失的照片。

在此我附上我的代碼：

#include <stdio.h> 
#include <stdint.h> 


int main(int argc, char *argv[]) 
{ 
    if (argc != 2) 
    { 

     fprintf(stderr, "Usage: ./recover file\n"); 
     return 1; 
    } 

    //declaring pointer infile and giving the address of argv[1]; 
    char *infile = argv[1]; 

    //Opening file 
    FILE *raw_data; 
    raw_data = fopen(infile, "r"); 

    //Checking for NULL error 
    if(raw_data == NULL) 
    { 
     fprintf(stderr, "Could not open file.\n"); 
     return 2; 
    } 


    uint8_t buffer[512];    //Delcaring unsigned int variable type. Array of 512 bytes. 
    int counter = 0;     //Declaring counter for counting jpegs files 

    FILE *outfile;     //Setting pointer named outfile for printing here 

    char filename[8];     //declaring 'filename' variable for storing the file's name 


    //While we can reads blocks of memory of 512 bytes from raw_data (aka the address from the infile) into buffer: 
    while (fread(buffer, 512, 1, raw_data)) 
    { 
     //Condition for tracking the first bytes that form a JPEG file 
     if(buffer[0] == 0xff && 
      buffer[1] == 0xd8 && 
      buffer[2] == 0xff && 
      (buffer[3] & 0xf0) == 0xe0) 
      { 


       if(counter == 0)        //If this is the 1st file, then name the file with 
                  //counter value with 3 digits (%03d) 
       {            
        sprintf(filename, "%03d.jpg", counter); // And 3 digits (%i3) 
        outfile = fopen(filename, "w");   //Open file named outfile in write mode 
        counter++; 
       } 

       else        //If this is not the first JPG opened, firstly close the 
       {         // current open file, and then open a new one with the 
        fclose(outfile);    // current counter value and 3 digits for its name 
        sprintf(filename, "%03d.jpg", counter); 
        outfile = fopen(filename, "w"); //Open file named 'outfile' in write mode 
        counter++; 

       } 


      } 

     fwrite(buffer, 1, sizeof(buffer), outfile); /* Write function that takes buffer data (aka the 
                 pointer to the array of elements to be written, 
                 writes 1 byte of elements of the syze buffer (512) 
                 and it writes it to the output, aka 'outfile' */ 
    } 
    fclose(outfile);   //Remember to close the last file once we get out of the while-loop 
} 

這裏是棘手的部分：

我已經成功地恢復所有問題的圖像。但是，如果我多次運行代碼，比如說5次，我最終會出現分段錯誤。

當我運行check50時，我收到以下消息（我將在一些成功的運行和check50 veredict後附上一個圖像，包含分段錯誤）。 Click here to see the image

我只是不明白。我建議記憶可能會有一些麻煩，但我只是不知道它是什麼。

非常感謝你的時間和你的幫助人。 StackOVerFlow總是這樣一個尋找指導的好地方。

編輯

如果我跑echo $?一旦分割故障提示，我得到的139

Here's the terminal prompt screenshot

編輯

正如@Thomas迪基值已經指出，該程序正在寫一個文件，不管是否有打開的文件。

我已經更新並修復了一下我的代碼，以保持它的清潔，並添加了if條件以修復它。

這裏的解決方案：

#include <stdio.h> 
#include <stdint.h> 


int main(int argc, char *argv[]) 
{ 
if (argc != 2) 
{ 

    fprintf(stderr, "Usage: ./recover file\n"); 
    return 1; 
} 

//declaring pointer infile and giving the address of argv[1]; 
char *infile = argv[1]; 

//Opening file 
FILE *raw_data; 
raw_data = fopen(infile, "r"); 

//Checking for NULL error 
if(raw_data == NULL) 
{ 
    fprintf(stderr, "Could not open file.\n"); 
    return 2; 
} 

uint8_t buffer[512];    //Delcaring unsigned int variable type. Array of 512 bytes. 

int counter = 0;     //Declaring counter for counting jpegs files 

FILE *outfile;     //Setting pointer named outfile for printing here 

char filename[8];     //declaring 'filename' variable for storing the file's name 


//While we can reads blocks of memory of 512 bytes from raw_data (aka the address from the infile) into buffer: 
while (fread(buffer, 512, 1, raw_data)) 
{ 
    //Condition for tracking the first bytes that form a JPEG file 
    if(buffer[0] == 0xff && 
     buffer[1] == 0xd8 && 
     buffer[2] == 0xff && 
     (buffer[3] & 0xf0) == 0xe0) 
     { 

      if(counter != 0)        
      {   
       fclose(outfile);      //If this is not the first JPG opened, close previous file 
      } 

      sprintf(filename, "%03d.jpg", counter); //print stream to 'filename' the value of 'counter' in 3 digits 
      outfile = fopen(filename, "w");   //Open file named outfile in write mode 
      counter++;        //Add 1 to counter 

     } 
     if(counter != 0)       //Don't start writing on a file until the first jpeg is found 
     { 
     fwrite(buffer, sizeof(buffer), 1, outfile);   /* - Write function that takes buffer data 
                    (aka the array of elements to be written) , 
                   - Write a block of 512 bytes of elements 
                    (aka the size of buffer), 
                   - 1 block of 512 bytes at a time, 
                   - And it writes it to the output, aka 'outfile' */ 
     }               

} 
fclose(outfile);   //Remember to close the last file once we get out of the while-loop 
return 0; 

}

Answer 1

程序只打開輸出文件，如果頭看起來不錯，但寫入到輸出irregardless。如果您閱讀的文件沒有jpeg標題，則會中斷。