Using fseek and ftell to determine the size of a file has a vulnerability?

Question

I\'ve read posts that show how to use fseek and ftell to determine the size of a file.

FILE *fp;
long file_size;
char *buffer;

fp = fopen(\"foo.bin\", \"r\         


        

Answer 1

The reason to not use fstat is that fstat is POSIX, but fopen, ftell and fseek are part of the C Standard.

There may be a system that implements the C Standard but not POSIX. On such a system fstat would not work at all.