Date: Mon, 22 Jan 2001 20:01:45 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Warner Losh <imp@harmony.village.org> Cc: Daniel Eischen <eischen@vigrid.com>, "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.BSF.4.21.0101221935540.27700-100000@besplex.bde.org> In-Reply-To: <200101212136.f0LLaM901943@harmony.village.org>
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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).
Bruce
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