From: Alexander Monakov <amonakov@ispras.ru>
To: musl@lists.openwall.com
Subject: Re: Explicit casts in ctype.h suppress compiler warnings
Date: Fri, 17 Apr 2015 21:24:09 +0300 (MSK) [thread overview]
Message-ID: <alpine.LNX.2.11.1504172059320.11963@monopod.intra.ispras.ru> (raw)
In-Reply-To: <20150417165238.GA6817@brightrain.aerifal.cx>
> In another place (math.h) I removed this type of compound literal
> usage because it was incompatible with C++, but the macros are
> suppressed in C++ anyway. Still they might break -pedantic with
> -std=c89. I do like this approach best in principle if it works
> though, because the rules for when an error occurs are basically the
> same as the rules for a real function.
I confirm that the idea works, and as Rich said it causes a warning with
-pedantic -std=c89 with gcc-4.5..4.7 (but not 4.8, 4.9).
> Do you have an idea in mind for how we could achieve that? I suspect
> the macros are still better optimizable than the inline function
> approach, so I'd lean towards doing a macro that avoids evaluating c
> and just checks its type, which would involve using ?: I think.
I admit I was thinking of doing isspace-style inlines everywhere, but thanks
to your suggestion I was able to come up with this:
static __inline void __is_int(int a) {}
#define isdigit(a) (__is_int(0?(a):0), ((unsigned)(a)-'0') < 10)
Actually, thinking about GCC behavior a bit more, I was lucky that there's a
warning for isspace in the first place: wrong argument to __isspace originates
in the context of a system-header-declared macro, so generally I'd say that
the same warning-suppression logic should have applied.
Alexander
next prev parent reply other threads:[~2015-04-17 18:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-17 10:59 Alexander Monakov
2015-04-17 16:49 ` Jens Gustedt
2015-04-17 16:52 ` Rich Felker
2015-04-17 18:24 ` Alexander Monakov [this message]
2015-04-17 18:35 ` Szabolcs Nagy
2015-04-17 19:43 ` Szabolcs Nagy
2015-04-17 20:21 ` Rich Felker
2015-04-17 20:32 ` Szabolcs Nagy
2015-04-17 20:34 ` Jens Gustedt
2015-04-17 21:36 ` Rich Felker
2015-04-18 2:03 ` Morten Welinder
2015-04-17 19:33 ` William Ahern
2015-04-17 16:50 ` Rich Felker
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