From: Xi Ruoyao <xry111@mengyan1223.wang>
To: Jonny Grant <jg@jguk.org>
Cc: gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: gcc warn unreached else {}
Date: Thu, 09 Jul 2020 23:00:28 +0800 [thread overview]
Message-ID: <6e02fef204a84b1015f8e1973f1236ff17721e4d.camel@mengyan1223.wang> (raw)
In-Reply-To: <3a091703-4842-b738-bb38-fab01e787650@jguk.org>
On 2020-07-09 10:45 +0100, Jonny Grant wrote:
> Hello!
>
> There is an example below, (my code is not like this example below). I'm
> reporting a possible issue, and asking if there is a way to detect it in code
> bases. If it's a real issue I can file a bug report on Bugzilla.
>
> Can gcc warn where code will not get to the 'return 3;' below?
>
> Cheers, Jonny
>
>
> int main(void)
> {
> const int i = 1;
> if(1 == i)
> {
> return 1;
> }
> else if(1 != i)
> {
> return 2;
> }
> else
> {
> return 3;
> }
> }
Generally finding all the branches in a program impossible to be executed is
unsolvable. Even in a program without any loop it's still NP-hard.
For some "simple" cases maybe we can implement some heuristics, or use a brute
force approach (as a part of -fanalyzer). But I doubt if these simple cases are
really useful.
--
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University
next prev parent reply other threads:[~2020-07-09 15:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 9:45 Jonny Grant
2020-07-09 15:00 ` Xi Ruoyao [this message]
2020-07-09 15:15 ` Jonny Grant
[not found] ` <e20bf113efcb7fe3e533ac694aa4bd62519b3654.camel@mengyan1223.wang>
2020-07-09 15:46 ` Xi Ruoyao
2020-07-09 15:46 ` Xi Ruoyao
[not found] ` <6d61e32f-3d69-9ac9-0a7e-88daa154c578@jguk.org>
2020-07-10 8:20 ` Xi Ruoyao
2020-07-10 21:50 ` Jonny Grant
2020-07-09 16:15 ` Martin Sebor
2020-07-16 0:20 ` Jonny Grant
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