Date: Mon, 7 Mar 2022 11:42:39 -0500 From: James Y Knight <jyknight@...gle.com> To: musl@...ts.openwall.com Cc: "wangjianjian (C)" <wangjianjian3@...wei.com> Subject: Re: basename with no parameter? Note that the C2x standard intends to remove deprecated non-prototype declarations, along with K&R-style non-prototype definitions. Empty parens in a declaration will be treated as a zero-arg prototype, just as in C++. (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2841.htm). Additionally, compilers may start emitting some default-on warnings for use of these deprecated features even in pre-C2x language modes, although that'd likely be suppressed for system headers. It'd probably be a good idea to remove any such hacks which depend on non-prototype declarations, to get ahead of these changes. On Mon, Mar 7, 2022 at 8:19 AM Rich Felker <dalias@...c.org> wrote: > On Mon, Mar 07, 2022 at 10:31:41AM +0800, wangjianjian (C) wrote: > > Hi all, > > > > I find that the basename in string.h with _GNU_SOURCE in Musl > > libc(Line 119): > > > > char *basename(); > > This is not a declaration with no parameter. It's a declaration > without any prototype. > > > The man page says that have two different version of basename > > however both need one parameter, is this correct? > > No, that's documenting glibc. There is only one version of basename in > musl and it's the standard one. > > The reason for the non-prototype declaration is explained in commit > 37bb3cce4598c19288628e675eaf1cda6e96958f: > > omit declaration of basename wrongly interpreted as prototype in C++ > > the non-prototype declaration of basename in string.h is an ugly > compromise to avoid breaking 2 types of broken software: > > 1. programs which assume basename is declared in string.h and thus > would suffer from dangerous pointer-truncation if an implicit > declaration were used. > > 2. programs which include string.h with _GNU_SOURCE defined but then > declare their own prototype for basename using the incorrect GNU > signature for the function (which would clash with a correct > prototype). > > however, since C++ does not have non-prototype declarations and > interprets them as prototypes for a function with no arguments, we > must omit it when compiling C++ code. thankfully, all known broken > apps that suffer from the above issues are written in C, not C++. > > This was from 2012, so it might make sense to do something different > now, like putting the correct prototype there and getting any programs > it still clashes with fixed. > > Rich > Content of type "text/html" skipped
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