[PATCH] support kernels without __ARCH_WANT_SYSCALL_NO_FLAGS

[Bernhard Reutner-Fischer]

On 26 April 2012 18:47, Rich Felker <dalias at aerifal.cx> wrote:
> On Thu, Apr 26, 2012 at 11:00:39AM -0400, Rich Felker wrote:
>> On Thu, Apr 26, 2012 at 10:18:11AM -0400, Mark Salter wrote:
>> > +#ifdef __NR_dup2
>> >  _syscall2(int, dup2, int, oldfd, int, newfd)
>> > +#elif defined __NR_dup3
>> > +#include <fcntl.h>
>> > +
>> > +int
>> > +dup2 (int fd, int fd2)
>> > +{
>> > +   /* For the degenerate case, check if the fd is valid (by trying to
>> > +      get the file status flags) and return it, or else return EBADF.  */
>> > +   if (fd == fd2)
>> > +           return __libc_fcntl(fd, F_GETFL, 0) < 0 ? -1 : fd;
>>
>> Is there a reason this special case is necessary? Not questioning it,
>> I just want to know.
>
> OK, I'll answer my own question: it seems to be a workaround for a
> kernel bug on 64-bit Linux:
>
> http://old.nabble.com/-PATCH--dup2:-Fix-return-value-with-oldfd-%3D%3D-newfd-and-invalid-fd-td23488867.html

Which, from the looks, was fixed in
6c5d0512a091480c9f981162227fdb1c9d70e555 so 2.6.27 and later do not
need this in libc.