Bug 120233
| Summary: | [libc] [patch] [request] FreeBSD is missing fcntl() operation F_DUP2FD | ||||||
|---|---|---|---|---|---|---|---|
| Product: | Base System | Reporter: | jau | ||||
| Component: | kern | Assignee: | Antoine Brodin <antoine> | ||||
| Status: | Closed FIXED | ||||||
| Severity: | Affects Only Me | ||||||
| Priority: | Normal | ||||||
| Version: | 6.3-STABLE | ||||||
| Hardware: | Any | ||||||
| OS: | Any | ||||||
| Attachments: |
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On Sun, 3 Feb 2008, Jukka Ukkonen wrote:
> I have had this modification in my own environments for some 4 years
> starting from FreeBSD-4.x with no ill effects. In fact in my own C library I
> have both dup() and dup2() only as wrappers for fcntl() and everything works
> just fine.
No opinion on the remainder of the patch, but just wanted to chime in on this
one point: once a system call is in the ABI, we generally won't ever remove
it. The reason is that this would break backward compatibility for older
binaries and libraries that encode the old system call. There may be an
argument for adding the new fcntl() interface, but there isn't really an
argument to remove the old system calls that overrides the need for backward
compatibility. I will generally comment that it's unfortunate that we end up
with many APIs for the same operation, though, but that's generally a concern
overriden by the need for portability.
Robert N M Watson
Computer Laboratory
University of Cambridge
Responsible Changed From-To: freebsd-bugs->antoine Take this. antoine 2008-03-08 22:02:21 UTC
FreeBSD src repository
Modified files:
lib/libc/sys fcntl.2
sys/kern kern_descrip.c
sys/sys fcntl.h
tools/regression/file/dup dup.c
Log:
Introduce a new F_DUP2FD command to fcntl(2), for compatibility with
Solaris and AIX.
fcntl(fd, F_DUP2FD, arg) and dup2(fd, arg) are functionnaly equivalent.
Document it.
Add some regression tests (identical to the dup2(2) regression tests).
PR: 120233
Submitted by: Jukka Ukkonen
Approved by: rwaston (mentor)
MFC after: 1 month
Revision Changes Path
1.46 +37 -1 src/lib/libc/sys/fcntl.2
1.325 +6 -1 src/sys/kern/kern_descrip.c
1.18 +1 -0 src/sys/sys/fcntl.h
1.3 +71 -2 src/tools/regression/file/dup/dup.c
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State Changed From-To: open->patched patched in HEAD. antoine 2008-04-20 19:32:46 UTC
FreeBSD src repository
Modified files: (Branch: RELENG_7)
lib/libc/sys fcntl.2
sys/kern kern_descrip.c
sys/sys fcntl.h param.h
tools/regression/file/dup dup.c
Log:
MFC to RELENG_7:
Introduce a new F_DUP2FD command to fcntl(2), for compatibility with
Solaris and AIX.
fcntl(fd, F_DUP2FD, arg) and dup2(fd, arg) are functionnaly equivalent.
Document it.
Add some regression tests (identical to the dup2(2) regression tests).
PR: 120233
Submitted by: Jukka Ukkonen
Approved by: rwaston (mentor)
MFC after: 1 month
Revision Changes Path
1.45.2.2 +37 -1 src/lib/libc/sys/fcntl.2
1.313.2.5 +6 -1 src/sys/kern/kern_descrip.c
1.16.18.2 +1 -1 src/sys/sys/fcntl.h
1.308.2.11 +1 -1 src/sys/sys/param.h
1.2.2.1 +71 -2 src/tools/regression/file/dup/dup.c
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State Changed From-To: patched->closed Close: committed in HEAD and RELENG_7. Thanks! |
This is a compatibility issue. At least SunOS/Solaris and AIX both have an fcntl() operation F_DUP2FD which is to dup2() as F_DUPFD is to dup(). Having support to this fcntl() operation would improve software portability between FreeBSD and other UNIX style systems. Additionally it would allow both dup() and dup2() be implemented as library functions narrowing down the system call API. This PR supersedes the 3.5 years old kern/70798 which provided the same feature for FreeBSD-4.10. The old ticket is still in the state open and nobody has cared as much as to say a simple "no" since its introduction. This PR contains an upgraded patch against FreeBSD-6.3 sources implementing the F_DUP2FD operation and a test program to show F_DUP2FD in action, if it is supported. I have had this modification in my own environments for some 4 years starting from FreeBSD-4.x with no ill effects. In fact in my own C library I have both dup() and dup2() only as wrappers for fcntl() and everything works just fine. Fix: Apply the attached patch. Patch attached with submission follows: How-To-Repeat: Try the test program shown below before and after applying the patch and notice the difference in its output. #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include <fcntl.h> #include <string.h> #include <stdio.h> #include <errno.h> static void dumpstat (st) struct stat *st; { printf ("st_dev = %ld\n", (long) st->st_dev); printf ("st_ino = %ld\n", (long) st->st_ino); printf ("st_nlink = %ld\n", (long) st->st_nlink); printf ("st_uid = %ld\n", (long) st->st_uid); printf ("st_gid = %ld\n", (long) st->st_gid); printf ("st_rdev = %ld\n", (long) st->st_rdev); } static void viewfdstat (fd) int fd; { struct stat st1; if (fstat (fd, &st1) < 0) { fprintf (stderr, "fstat(%d): %s\n", fd, strerror (errno)); } else { printf ("fstat(%d):\n", fd); dumpstat (&st1); } } int main (ac, av) int ac; char *av[]; { int fd; viewfdstat (0); fd = open ("/dev/null", O_RDWR, 0); viewfdstat (fd); #ifndef F_DUP2FD #define F_DUP2FD F_DUPFD #warning This system does not support F_DUP2FD. #endif if (fcntl (fd, F_DUP2FD, 0) < 0) { fprintf (stderr, "fcntl(%d, F_DUP2FD, 0): %s\n", fd, strerror (errno)); } viewfdstat (0); return (0); }