Re: gcc warn when pointers not checked non-null before de-referencing.

[Xi Ruoyao <xry111@mengyan1223.wang>]

On Sun, 2021-06-13 at 23:30 +0100, Jonny Grant wrote:
> Hello
> 
> This isn't real code, just an example to show.
> 
> I've tried with:  -Wall -Wextra -O2  and some other warnings, but
> couldn't get this to generate a warning that *g was possibly de-
> referenced. May I ask, does GCC have a way to get warnings when pointers
> are not checked?
> I had a look but -Wnull-dereference didn't help.
> 
> #include <stdlib.h>
> 
> #include <cstddef>
> void f(int * g)
> {
>     *g = 1;
> 
>     if(NULL == g)
>     {
>         exit(1);
>     }
> }
> 
> Best regards Jonny

It was explained by Chris Lattner at
http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_21.html

GCC (<= 4.4) had -Wunreachable-code which might work for this case.  But
it was too unreliable (as Chris said, generally there is no reliable way
to do this) and removed in later releases.
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University