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Subject: [Bug c++/25689] missed diagnostic about assignment used as truth
 value.
Date: Fri, 29 Apr 2022 02:59:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D25689

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:654f6978cdc85a3970ff2c478d4df3e55cf4d3ab

commit r13-23-g654f6978cdc85a3970ff2c478d4df3e55cf4d3ab
Author: Zhao Wei Liew <zhaoweiliew@gmail.com>
Date:   Tue Feb 15 17:44:29 2022 +0800

    c++: Add diagnostic when operator=3D is used as truth cond [PR25689]

    When compiling the following code with g++ -Wparentheses, GCC does not
    warn on the if statement. For example, there is no warning for this cod=
e:

    struct A {
            A& operator=3D(int);
            operator bool();
    };

    void f(A a) {
            if (a =3D 0); // no warning
    }

    This is because a =3D 0 is a call to operator=3D, which GCC does not ha=
ndle.

    This patch fixes this issue by handling calls to operator=3D when decid=
ing
    to warn.

    Bootstrapped and regression tested on x86_64-pc-linux-gnu.

            PR c++/25689

    gcc/cp/ChangeLog:

            * call.cc (extract_call_expr): Return a NULL_TREE on failure
            instead of asserting.
            (build_new_method_call): Suppress -Wparentheses diagnostic for
            MODIFY_EXPR.
            * semantics.cc (is_assignment_op_expr_p): Add function to check
            if an expression is a call to an op=3D operator expression.
            (maybe_convert_cond): Handle the case of a op=3D operator expre=
ssion
            for the -Wparentheses diagnostic.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wparentheses-31.C: New test.

    Signed-off-by: Zhao Wei Liew <zhaoweiliew@gmail.com>=