jv@mhres.mh.nl (Johan Vromans) (01/31/89)
A program using the "rename" system call gets problems when
linked with -lPW:
$ cat t.c
main () {
rename(0,0);
}
$ cc t.c
$ cc t.c -lPW
ld: Undefined external -
_Error
ld: output file still contains undefined symbols
ld: (Warning) did not generate an output file
--
Johan Vromans jv@mh.nl via european backbone (mcvax)
Multihouse [A-Za-z ]* [NB]V uucp: ..!mcvax!mh.nl!jv
Gouda - The Netherlands phone: +31 1820 62944marc@hpfcdc.HP.COM (Marc 'Sphere' Sabatella) (02/03/89)
/ hpfcdc:comp.sys.hp / jv@mhres.mh.nl (Johan Vromans) / 6:34 am Jan 31, 1989 / >A program using the "rename" system call gets problems when >linked with -lPW: >... > $ cc t.c -lPW > ld: Undefined external - > _Error To be honest, I do not know what libPW.a is, but a little poking around and disassebly turned up a few things: "libPW.a" defines its own version of 'rename', which seems to do basically the same thing as the regular 'rename'. One difference is that some of the internal libPW.a routines called by 'rename' use a string variable called "Error" to construct error messages, as in if (link(p1,p2)) { sprintf(Error,"can't link `(%s)' to `(%s)' (%d)",p2,p1,0x70); fatal(Error); } Error does not seem to be defined anywhere in libPW.a; but if this is your only problem with libPW, you could try declaring char Error[80]; somewhere in your program. -------------- Marc Sabatella HP Colorado Language Lab marc%hpfcrt@hplabs.hp.com
bd@hp-ses.SDE.HP.COM (Bob Desinger) (02/04/89)
Johan Vromans (jv@mhres.mh.nl) writes: > A program using the "rename" system call gets problems when > linked with -lPW: > $ cc t.c -lPW > ld: Undefined external - > _Error I get that on my 6.2 s300, too, when I link with -lPW. But when I don't use -lPW, I get the libc version of rename() that successfully links. Can you use that instead? (If you need other routines from the PWB, you may need to use "-lc -lPW" flags for the linker.) A look at some older HP-UX code for another architecture shows that the libc version is a real system call instead of a library call; it's a stub that jumps to the kernel routine. In this older code, the libPW version of rename() calls two other libPW routines, xlink() and xunlink(). xlink() declares Error as an extern char buffer, used by sprintf() and another call, no doubt for temporary storage to hold the formatted error message. I have never looked at any s300 source code, much less the 6.2 version, so I don't know if it's similar. I was hoping to find some magic linker flags or #include files mentioned on the PWB man page, but I couldn't find any man pages for PWB entry points on either the 300 or 800. Or, for that matter, in 4.3BSD or the SVID or even the Lapin book on "Portable C and Unix System Programming." I suppose I shouldn't be surprised; PWB was an internal Bell Labs thing, according to Lapin. Grepping through /usr/include/*.h and /usr/include/sys/*.h turns up two useful references to Error on the s300: /usr/include/macros.h:extern char Error[128]; /usr/include/oldmacros.h:char Error[128]; You definitely want <oldmacros.h> here. By the way, <oldmacros.h> doesn't appear on the s800---and you'll get the same error message if you use -lPW without -lc there, too. So if you can possibly switch to the kernel version in libc, do it for greater portability. -- bd
guy@auspex.UUCP (Guy Harris) (02/05/89)
>A look at some older HP-UX code for another architecture shows that >the libc version is a real system call instead of a library call; it's >a stub that jumps to the kernel routine. The kernel routine most likely has two other advantages: 1) it allows non-super-users to rename directories 2) it works over NFS to servers that don't allow you to create multiple links to files and it is also allegedly atomic, or at least mostly atomic. To quote from the comment that appears (perhaps with minor typographical changes) in various flavors of UNIX: * ...The essential operation is: * unlink(target); * link(source, target); * unlink(source); * but "atomically". Can't do full commit without saving state in the inode * on disk, which isn't feasible at this time. Best we can do is always * guarantee that the TARGET exists. >... but I couldn't find any man pages for PWB entry points... I >suppose I shouldn't be surprised; PWB was an internal Bell Labs thing, >according to Lapin. Sort of internal. PWB/UNIX 1.0 actually was released; it was based on V6 UNIX, mostly (although with later versions of kernel, C compiler, some library routines, etc. and standard I/O, most of which came out of Research in various forms as well). I think there may even have been a document for the routines in the "-lPW" library; said documentation had disappeared by the time S3 came out, though. >So if you can possibly switch to the kernel version in libc, do it for >greater portability. Definitely. Not all flavors of UNIX have "-lPW", and it may even disappear from AT&T's releases someday.... (And yes, "rename" will be in S5R4; it's already in the POSIX spec.)
jv@mhres.mh.nl (Johan Vromans) (02/05/89)
To all people (mostly HP representatives) who replied to my name clash problem: thanks a lot! The application (the alpha test version of smail3.1) uses the regex/regcmp routines from libPW.a . So I extracted them from libPW.a and added them to the application's objects. Easy and effective. -- Johan Vromans jv@mh.nl via european backbone (mcvax) Multihouse [A-Za-z ]* [NB]V uucp: ..!mcvax!mh.nl!jv Gouda - The Netherlands phone: +31 1820 62944