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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106774] warning about comparison to true/false
Date: Wed, 31 Aug 2022 10:33:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106774

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Blocks|                            |87403

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Frank Heckenbach from comment #2)
> This should cover all cases mentioned:
>=20
> void t (bool a, int i, float e, double f)
> {
>   // Boolean literal comparisons
>   if (a =3D=3D true)  // better: if (a)
>     return;
>   if (a =3D=3D false)  // better: if (!a)
>     return;
>   if (a !=3D true)  // better: if (!a)
>     return;
>   if (a !=3D false)  // better: if (a)
>     return;
>   // also reversed to be sure
>   if (true =3D=3D a)  // better: if (a)
>     return;
>   if (false !=3D a)  // better: if (a)
>     return;

These are definitely coding style, and I don't think a warning is warranted.

>=20
>   // Integer comparisons to Boolean literals
>   if (i =3D=3D true)  // better: if (i =3D=3D 1)

Or maybe it was meant to be ((bool)i =3D true).

Warning for these does seem more useful IMO. The arithmetic promotions from
bool to int (or float) mean the comparison doesn't do what it appears to do,
and there seems no reason to use a true/false literal there.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D87403
[Bug 87403] [Meta-bug] Issues that suggest a new warning=