From: Martin Sebor <msebor@gmail.com>
To: Jason Merrill <jason@redhat.com>
Cc: Gcc Patch List <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] restore -Wunused-variable on a typedef'd variable in a function template (PR 79548)
Date: Wed, 22 Feb 2017 07:48:00 -0000 [thread overview]
Message-ID: <0a4c97ac-fe30-2e3e-6694-9a3f9dbdf90c@gmail.com> (raw)
In-Reply-To: <CADzB+2=D+cU8Lnq5eGqJzo=cXjL_YPHaj1M_RtnwxR97keYsug@mail.gmail.com>
> Ah, I see, your patch changes attribute unused handling for local
> variables from tracking TREE_USED to lookup_attribute. I'm not
> opposed to this change, but I'd like to understand why the TREE_USED
> handling wasn't working.
In the test case in the bug:
template <class T>
void g ()
{
T t; // warning, ok
typedef T U;
U u; // no warning, bug
}
template void g<int>();
both TREE_USED(T) and TREE_USED(t) are zero in initialize_local_var
so the function doesn't set already_used or TREE_USED(t) and we get
a warning as expected.
But because TREE_USED(U) is set to 1 in maybe_record_typedef_use
(to implement -Wunused-local-typedefs), initialize_local_var then
sets already_used to 1 and later also TREE_USED(u) to 1, suppressing
the warning.
Martin
next prev parent reply other threads:[~2017-02-22 0:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-18 2:29 Martin Sebor
2017-02-21 18:10 ` Jason Merrill
2017-02-21 19:09 ` Martin Sebor
2017-02-21 20:35 ` Jason Merrill
2017-02-22 7:48 ` Martin Sebor [this message]
2017-02-22 18:10 ` Jason Merrill
2017-02-22 23:52 ` Martin Sebor
2017-02-23 1:11 ` Jason Merrill
2017-02-23 21:06 ` Martin Sebor
2017-02-23 23:48 ` Jason Merrill
2017-03-20 21:12 ` Jason Merrill
2017-03-21 18:40 ` Martin Sebor
2017-03-21 19:28 ` Jason Merrill
2017-03-21 22:37 ` Martin Sebor
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