From: "Hans-Bernhard Bröker" <HBBroeker@t-online.de>
To: cygwin@cygwin.com
Subject: Re: free() and implicit conversion to a function pointer
Date: Thu, 16 Mar 2017 23:49:00 -0000 [thread overview]
Message-ID: <33519566-7f9a-ad78-6160-ccfa6465c279@t-online.de> (raw)
In-Reply-To: <58CB07A8.9010401@tlinx.org>
Am 16.03.2017 um 22:46 schrieb L A Walsh:
> Going by subj and talk below, this is a bit confusing...
>
> But it looks like you are testing 'free' for a value?
Not really. The idea is to test free for _exixtence_. Which only makes
sense in case of weak symbol support getting involved. In other
situations, there could not possibly be a need for a run-time if() test,
because surely the code could know at build time whether free() exists
or not.
> Isn't standard 'free' declared to take 1 arg and
> return void?
Yes. But since the code in question doesn't actually _call_ free,
that's both irrelevant.
> If you aren't talking standard 'free()', then
> nevermind...
We are talking standard free. More to the point, we're discussing
newlib, the package that actually implements free() for cygwin.
>> The only code that might actually be a slight bit better than the given
>>
>> if (! free)
>>
>> would be
>>
>> if (0 != free)
>>
>> The function designator `free' auto-decays into a function pointer,
>> which is compared to a null pointer constant: 0. The ! operator does
>> that same thing implicitly, but is fully equivalent to it.
> ---
> Free autodecays to a function pointer?
In the use case at hand: yes, it does.
> In what language?
Standard C.
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next prev parent reply other threads:[~2017-03-16 23:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <c5af0608-17c4-2270-dbba-c3b704c9226e@t-online.de>
2017-03-16 19:25 ` free() and implicit conversion to a function pointer (was: Use of initialized variable in strtod.c) Hans-Bernhard Bröker
2017-03-16 21:46 ` free() and implicit conversion to a function pointer L A Walsh
2017-03-16 23:49 ` Hans-Bernhard Bröker [this message]
2017-03-17 8:30 ` Corinna Vinschen
2017-03-17 21:01 ` Hans-Bernhard Bröker
2017-03-20 18:43 ` Eric Blake
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