Messages in this thread | | | Date | Thu, 09 Oct 2008 13:43:02 -0700 | From | "H. Peter Anvin" <> | Subject | Re: dup2() vs dup3() inconsistency when |
| |
Ulrich Drepper wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > H. Peter Anvin wrote: >> The dup2() behavior comes from the logical consequence of dup2()'s >> "close on reuse"; one would think it would be logical for dup3() to >> behave the same way. > > No. We deliberately decided on this change. Otherwise, what is the > result of dup3(fd, fd, O_CLOEXEC)? There is no reason to use > dup2(fd,fd), so why the hell somebody wants to defend this is beyond me. >
The result of dup3(fd, fd, O_CLOEXEC) is to set the O_CLOEXEC flag on fd.
The behaviour of dup2() is functionally the following:
1. Duplicate the file descriptor from file_table[oldfd]. 2. If file_table[newfd] is in use, close it. 3. Install the duplicate file descriptor at file_table[newfd].
Step (2) could be considered a bit dubious, but the behaviour of dup2(fd, fd) is a direct consequence of the chosen semantics.
-hpa
| |