C Error: Cannot fopen a file using the same name after fclose it

Question

在这个任务中，我需要创建多个 JPEG 文件。每次，在我打开下一个文件之前，都会打开、写入和关闭一个文件。然而，当我再次命名文件 outptr 时它显示错误，尽管我在打开新文件之前关闭了文件。你能告诉我这里出了什么问题吗？

错误信息如下：

recover.c:51:23: error: declaration shadows a local variable [-Werror,-Wshadow]
                FILE *outptr = fopen(outfile, "w");
                      ^
recover.c:25:11: note: previous declaration is here
    FILE *outptr = fopen("000.jpg", "w");
          ^
1 error generated.

这是我的原始代码：

int main(int argc, char *argv[])
{
    // Number of bytes in a block
    const int BLOCK_SIZE = 512;

    // Open input file
    FILE *infile = fopen(argv[1], "r");
    if (infile == NULL)
    {
        fprintf(stderr, "Could not open %s.\n", argv[1]);
        return 1;
    }


    //File name
    char outfile[7];

    // Create a buffer to copy data
    int16_t buffer[512];
    // Open a random file
    FILE *outptr = fopen("000.jpg", "w");

    int i = -1;


    while (i < 50)
    {
        // While not end of memory card
        while (!(buffer[0] == 0x00 && buffer[1] == 0x00 && buffer[2] == 0x00 && i == 50))
        {
            fread(buffer, sizeof(int16_t) * 512, 1, infile);

            // Check if this block marks the beginning of a new picture
            if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff)
            {
                // Increase file number
                i += 1;

                // Close current output file
                fclose(outptr);

                // Output file name
                sprintf(outfile, "%03d.jpg\n", i);
    
                // Open new output file
                FILE *outptr = fopen(outfile, "w");
                if (outptr == NULL)
                {
                    fclose(infile);
                    fprintf(stderr, "Could not create %s.\n", outfile);
                    return 1;
                }

                // Write buffer to new file
                fwrite(buffer, sizeof(int16_t) * 512, 1, outptr);
            }
            else
            {
                // Write buffer to current file
                fwrite(buffer, sizeof(int16_t) * 512, 1, outptr);
            }

        }
        // Increase i to 50 and break the while loop
        i += 1;
        // Close current output file
        fclose(outptr);
    }
    // Close files
    fclose(infile);
}

Answer 1

您在代码块中重新定义了 outptr。在同一个代码块中，您使用了外部作用域变量。这在 C 中是不合法的。修复是这样的：

将 while 内 if 块中的 FILE *outptr = fopen(outfile, "w"); 替换为：
outptr = fopen(outfile, "w");

C Error: Cannot fopen a file using the same name after fclose it

C Error: Cannot fopen a file using the same name after fclose it

c

error-handling

fopen

fwrite

fclose