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From: "f.heckenbach@fh-soft.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106774] New: warning about comparison to true/false
Date: Mon, 29 Aug 2022 23:48:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106774

            Bug ID: 106774
           Summary: warning about comparison to true/false
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: f.heckenbach@fh-soft.de
  Target Milestone: ---

gcc has "-Wbool-compare" to warn about boolean expression compared with an
integer value different from true/false. This warning is enabled by -Wall.

However, a warning for comparisons with true and false may also be useful. =
The
former is redundant, the latter can be replaced with "!".

Actually, this warning may also be given when comparing a non-Boolean integ=
ral
expression with true or false. The former is not redundant, but may often n=
ot
be what's intended (if so, one should compare with 1). The latter is equiva=
lent
to comparing with 0, but still strange style. And comparing non-integral (e=
.g.
floating-point) expressions with Boolean literals is certainly warning-wort=
hy
(though it may be caught by "-Wfloat-equal" as well).

To sum up, a new warning about comparing any expression with true/false
literals.=20

Maybe something like "-Wbool-compare=3D2" (which would not be enabled by -W=
all, I
guess; maybe by -Wextra, but even if it must be given manually, I'd find it
useful).=