Date: Mon, 22 Jan 2001 05:27:47 -0500 (EST) From: Daniel Eischen <eischen@vigrid.com> To: Bruce Evans <bde@zeta.org.au> Cc: Warner Losh <imp@harmony.village.org>, "Jacques A. Vidrine" <n@nectar.com>, arch@FreeBSD.ORG Subject: Re: Request For Review: libc/libc_r changes to allow -lc_r Message-ID: <Pine.SUN.3.91.1010122051818.17483B@pcnet1.pcnet.com> In-Reply-To: <Pine.BSF.4.21.0101221935540.27700-100000@besplex.bde.org>
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On Mon, 22 Jan 2001, Bruce Evans wrote: > On Sun, 21 Jan 2001, Warner Losh wrote: > > > In message <Pine.SUN.3.91.1010121162703.14751A-100000@pcnet1.pcnet.com> Daniel Eischen writes: > > : Oops, sorry, I missed the second question. You need _foo to be > > : used within libc, so that when libc_r/libpthread is linked in, > > : it can provide a replacement function for it. We also need to > > : determine if the function is a cancellation point or not, so > > : if you just had foo and __sys_foo, libc_r/libpthread would have > > : no way of knowing if foo was called from within libc or from > > : the user application. The former is not a cancellation point, > > : while the latter is (if foo is read for example). > > > > I understand that. I guess my question is why name it _foo instead of > > __foo? I see the need for the tripartiteness, just not the need to > > call it _foo. > > (1) Underscores are verbose and ugly. > (2) _foo is usually sufficient. _[a-z] is not entirely in the user > namespace like you are claimed. From the 1990 ISO standard: > "All identifiers that begin with an underscore are always > reserved for use as identifiers with file scope in both the > ordinary identifier and tag name spaces". In practice, this > means that the implementation can use names beginning with > _[a-z] except for macro names and global variables that are > used in macros. E.g., errno must be defined as (*__error()) > and not as (*_error()), since the latter would break the > standard-conforming application code: > #include <errno.h> > void foo(void) { int _error = errno; } > A single underscore is sufficient in all other cases. E.g., > struct member names are in a nested namespace so they don't > conflict with variable names at all. They may still need a > single underscore so that they don't conflict with macro > names. > (3) We have some precedence for using _foo. > (4) NetBSD uses _foo (at least in old versions). How about this compromise: __sys_foo(T), _foo(W), foo(W). Noone but libc_r, except perhaps for exit.c, needs to reference __sys_foo. Poking around with nm on Solaris seems to show that they use __foo for system calls, and _bar for library functions. -- Dan Eischen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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