Re: [PATCH] wrapper: Fix a errno discrepancy on NetBSD.

[Junio C Hamano <gitster@pobox.com>]

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> On 2025-05-02 at 23:33:32, Collin Funk wrote:
>> As documented on NetBSD's man page, open with the O_NOFOLLOW flag and a
>> symlink returns -1 and sets errno to EFTYPE which differs from POSIX.
>> This patch fixes the following test failure:
>> 
>> $ sh t0602-reffiles-fsck.sh --verbose
>> --- expect	2025-05-02 23:05:23.920890147 +0000
>> +++ err	2025-05-02 23:05:23.916794959 +0000
>> @@ -1 +1 @@
>> -error: packed-refs: badRefFiletype: not a regular file but a symlink
>> +error: unable to open '.git/packed-refs': Inappropriate file type or format
>> not ok 12 - the filetype of packed-refs should be checked
>> 
>> This portability issue was introduced in Commit
>> cfea2f2da8 (packed-backend: check whether the "packed-refs" is regular file, 2025-02-28)
>> 
>> Signed-off-by: Collin Funk <collin.funk1@gmail.com>
>> ---
>>  wrapper.c | 14 +++++++++++++-
>>  1 file changed, 13 insertions(+), 1 deletion(-)
>> 
>> diff --git a/wrapper.c b/wrapper.c
>> index 3c79778055..4d448d7c57 100644
>> --- a/wrapper.c
>> +++ b/wrapper.c
>> @@ -737,7 +737,19 @@ int is_empty_or_missing_file(const char *filename)
>>  int open_nofollow(const char *path, int flags)
>>  {
>>  #ifdef O_NOFOLLOW
>> -	return open(path, flags | O_NOFOLLOW);
>> +	int ret = open(path, flags | O_NOFOLLOW);
>> +#ifdef __NetBSD__
>> +	/*
>> +	 * NetBSD sets errno to EFTYPE when path is a symlink. The only other
>> +	 * time this errno occurs when O_REGULAR is used. Since we don't use
>> +	 * it anywhere we can avoid an lstat here.
>> +	 */
>> +	if (ret < 0 && errno == EFTYPE) {
>> +		errno = ELOOP;
>> +		return -1;
>> +	}
>> +#endif
>> +	return ret;
>
> This patch seems reasonable and correct.  I don't use NetBSD, but I do
> often test there, and I'm aware of this infelicity.  I'm surprised we
> haven't hit it before.

Thanks, both.  Will queue after fixing the proposed log message a
bit (the sample must be indented, especially when it contains lines
that look like a patch).

> I suspect we'll also hit this on FreeBSD, which has a similar issue in
> that it returns `EMLINK` instead of `ELOOP`.

I won't expect Collin or you to redo this patch to cover FreeBSD;
anybody with FreeBSD box/vm can do a separate patch on a different
day.

> I do wish these two OSes
> would provide an appropriate POSIX-compatible `open` call when set with
> `_POSIX_SOURCE`, since this is one of the biggest portability problems
> with them.

That may be true, but not something we can fix here X-<.