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From: "vlad at petric dot cc" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/96543] New: null check on template pointer parameter fails
Date: Sun, 09 Aug 2020 23:00:44 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 10.2.1
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96543

            Bug ID: 96543
           Summary: null check on template pointer parameter fails
           Product: gcc
           Version: 10.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vlad at petric dot cc
  Target Milestone: ---

static unsigned c =3D 0;

template <unsigned* c>
struct A {
  static void test() {
    if constexpr (c) ++ *c;
  }
};

int main() {
  A<&c>::test();
  A<nullptr>::test();
}

The error is:

bug.cc: In instantiation of =E2=80=98static void A<c>::test() [with unsigne=
d int* c =3D
(& c)]=E2=80=99:
bug.cc:11:10:   required from here
bug.cc:11:5: error: the address of =E2=80=98c=E2=80=99 will never be NULL [=
-Werror=3Daddress]
   11 |   A<&c>::test();

The only fix is to remove the if constexpr (nothing else helps).=