Why does `fseek(..., 0, SEEK_CUR)` fail on windows?

The fseek() function is used to set the file position indicator for a given stream. When using fseek(stream, 0, SEEK_CUR), you are attempting to seek to the current position in the file. This operation is generally expected to be successful, but there are some cases where it might fail, especially on Windows.

One possible reason for failure on Windows is related to the way files are opened in different modes, like binary or text mode. On Windows, if a file is opened in text mode (using "t" flag in fopen()), newline characters (\n) might be translated to a carriage return and line feed (\r\n) sequence when writing to the file, and vice versa when reading from the file. This translation can cause the file position indicator to be different in binary and text mode, leading to unexpected results when using fseek().

To avoid issues with seeking in text mode, it's recommended to open the file in binary mode ("b" flag in fopen()) on Windows. This ensures that the file position indicator behaves consistently across platforms.

Here's an example of how you might use fopen() with binary mode:

cCopy code
#include <stdio.h>



int main() {

    FILE* file = fopen("myfile.txt", "rb");  // Open in binary mode

    if (file == NULL) {

        perror("Error opening file");

        return 1;

    }



    // Perform other file operations, including fseek



    fclose(file);

    return 0;

}

If you still encounter issues with fseek() failing on Windows, there might be other factors at play, such as file permissions, file sharing issues, or other system-specific conditions. In such cases, it might be helpful to provide more details about your code and the specific circumstances where the fseek() operation is failing.