Date: Wed, 6 Jul 2011 14:57:38 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Subject: Re: errno (was: Weekly reports - B) * Solar Designer <solar@...nwall.com> [2011-07-06 15:35:08 +0400]: > On Mon, Jun 13, 2011 at 12:54:18AM -0400, Rich Felker wrote: > > ... errno is a macro and has been for a > > long time (ever since threads) on most systems. It's required by the > > standard to be an lvalue macro. > > Any idea why glibc has __set_errno() internally instead of assigning to > its errno directly, then? The implementation for __set_errno() does a > direct assignment anyway. What did the glibc developers need it seems there was a different definition under sysdeps until 2002-07-19 Ulrich Drepper <drepper@...hat.com> * sysdeps/generic/bits/errno.h: Remove __set_errno definition. * ... and then 2002-11-25 Jakub Jelinek <jakub@...hat.com> * include/errno.h (__set_errno): Define as errno = val unconditionally. in older glibc eg sysdeps/unix/sysv/linux/bits/errno.h had code like #ifdef _ERRNO_H # undef EDOM # undef EILSEQ # undef ERANGE # include <linux/errno.h> /* Linux has no ENOTSUP error code. */ # define ENOTSUP EOPNOTSUPP /* Linux also has no ECANCELED error code. Since it is not used here we define it to an invalid value. */ # define ECANCELED 125 # ifndef __ASSEMBLER__ /* We now need a declaration of the `errno' variable. */ extern int errno; /* Function to get address of global `errno' variable. */ extern int *__errno_location __P ((void)) __attribute__ ((__const__)); # if defined _LIBC /* We wouldn't need a special macro anymore but it is history. */ # define __set_errno(val) (*__errno_location ()) = (val) # endif /* _LIBC */ # if !defined _LIBC || defined _LIBC_REENTRANT /* When using threads, errno is a per-thread value. */ # define errno (*__errno_location ()) # endif # endif /* !__ASSEMBLER__ */ #endif /* _ERRNO_H */
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