Re: windows exit codes truncated to 1 Byte

[Eric Blake <eblake@redhat.com>]

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On 03/31/2016 07:30 AM, Björn Stabel wrote:
> Am 31.03.2016 um 15:01 schrieb Cristian:
>> I noted that exit codes returned by CMD and other apps (msiexec) are truncated to 1 byte (0 .. 255).

This matches Linux, but not POSIX.

>> Windows exit codes are represented using 32 bits, so is this limitation intentional?

Part intentional (we do what Linux does), and part accidental (Cygwin
handles the return status slightly different than Windows, and that
handling makes it impossible to easily preserve all 32-bits, even if
Linux were to be patched to obey POSIX).

> POSIX specifies that the lower 8 bits of the exit status be made
> available to the caller of wait/waitpid:
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/wait.html

Correct: wait() and waitpid() can only return 8 bits; but POSIX states
that waitid() MUST be able to access all 32-bits untruncated; this is
where Linux gets it wrong (Linux truncates during exit(), so waitid()
can only return 8 bits; other operating systems do NOT truncate during
exit, but preserve all 32 bits; if you use wait() or waitpid() you only
get 8 bits, but if you use waitid() you can see the full 32 bits).

> Maybe there's another way to get the entire status value, but this looks
> like a POSIX limitation to me.
> Cygwin is conformant here.

Cygwin is only partially conformant here.

See also: http://austingroupbugs.net/view.php?id=947

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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