Why fopen_s returns EEXIST (errno 17) when opening file for reading

Question

When I execute fopen_s(&fid, FILE_NAME, "r"), fid is null and errno is 17.
How is this even possible that when I try to open a file for reading I get EEXIST error?

Sometimes, it has to do with an invalid path. Specifically, if a directory is specified in FILE_NAME, and that directory does not exist... It would be helpful if more detail were supplied so that the context of the call could be examined. — Mahonri Moriancumer, Jul 15 '14 at 14:44
When I change the directory name of the file name I get the error: "No such file or directory" — fudge, Jul 15 '14 at 14:55
Do you know the file you are trying to open exists? Do you know if the program you are running has permission to read the directory and file? — jxh, Jul 15 '14 at 14:56
Yes, it exists. And yes I have permissions. No permission is a different error. EEXIST is "File exist" error which should only happen if the open operation doesn't make sense if the file doesn't exist. — fudge, Jul 15 '14 at 15:01

score 3 · Answer 1 · answered Jul 15 '14 at 15:16

errno is not meaningful after a call to fopen_s. The error code is in the return value of the function.

Source: C11 Annex K, K.3.5.2.2 The freopen_s function, paragraph 9:

The fopen_s function returns zero if it opened the file. If it did not open the file or if there was a runtime-constraint violation, fopen_s returns a nonzero value.

Why fopen_s returns EEXIST (errno 17) when opening file for reading

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