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C:\temp>gcc -dM -E t.c |grep DOS
#define DOSERROR_STR _DOSERROR_STR
#define DOSERROR _DOSERROR
*#define __MSDOS__ 1*
#define MSDOS 1
#define __MSDOS 1
On Wed, Jun 16, 2021 at 2:10 PM Mark Olesen ***@***.***> wrote:
> If I do a search on "readdir ENOENT" there are some java references that
> pop, which check for this condition as well. I guess the only way to really
> find out is to reach out to kernel developers for various operating systems?
>
> SIDE NOTE: Various compilers use different macros to specify DOS.
> OpenWatcom uses '__DOS__'
>
> I believe __DOS__ is also used in DJ Delories gcc/g++ implementation (it's
> been awhile so I am being lazy and not confirming).
>
> MSDOS <http://en.wikipedia.org/wiki/MS-DOS>
> Type Macro
> Identification MSDOS
> Identification __MSDOS__
> Identification _MSDOS
> Identification __DOS__
> https://sourceforge.net/p/predef/wiki/OperatingSystems/
>
>
>
> On Wed, Jun 16, 2021 at 1:49 PM Albrecht Schlosser <
> ***@***.***> wrote:
>
>> Looking at the GNU implementation of readdir, it seems evident that ENOENT
>> should be checked for correctness as an EOF condition.
>>
>> No, Mark, that's not true. Please *do not take the ENOENT error
>> condition literally*. In the example code you posted (a link to) this is
>> the error code returned by the system (kernel) function getdents() which
>> in this case is turned into an EOF (end of directory) condition for
>> whatever reason (doesn't matter). This is a special case on "some systems"
>> (citation) and has absolutely nothing to do with our case here on DOS.
>>
>> We do not know why the DOS function readdir() returns ENOENT at the end
>> of the directory. Maybe this is ancient history and has never been changed
>> for backwards compatibility. You can't conclude from the (likely Linux
>> kernel) implementation of getdents() on the result of the DOS function
>> readdir(). The ENOENT errno value of POSIX readdir() is definitely an
>> error condition and not just "end of directory".
>>
>> The question we need to answer is how we deal with this condition. An
>> easy (pseudo code) solution would be, partly as Greg suggested, using #ifdef
>> MSDOS for the decision:
>>
>> #ifdef MSDOS /* MSDOS readdir() returns ENOENT on end of directory */
>> if ((!errno) || (ENOENT == errno))
>> #else /* POSIX compliant readdir()
>> if (!errno)
>> #endif
>>
>> ... or something like this ...
>>
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