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From: "yyc1992 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/100161] New: Impossible to suppress Wtype-limits warning
 involving template parameter.
Date: Tue, 20 Apr 2021 18:50:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100161

            Bug ID: 100161
           Summary: Impossible to suppress Wtype-limits warning involving
                    template parameter.
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yyc1992 at gmail dot com
  Target Milestone: ---

If a comparison involving a template parameter is always true or false, it
should not raise a warning if it could take other values for other template
parameters.

In particular, the type-limits warning from the code below,

```
void f(unsigned);

template<unsigned n>
void g()
{
    for (unsigned i =3D 0; i < n; i++) {
        f(i);
    }
}

void h()
{
    g<0>();
}
```

seems to be impossible to suppress. I think this is a regression around GCC=
 9
time. (I remember seeing it roughly around the same time/slightly after
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D90728)

This is partially related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=
=3D95148
(which would at least provide a way to suppress the warning).
Also somewhat related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D816=
42
though supposedly the C++ template example given there is fixed.=