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From: "joseph.h.garvin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/52299] New: GCC warns on compile time division by zero erroneously
Date: Fri, 17 Feb 2012 20:00:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D52299

             Bug #: 52299
           Summary: GCC warns on compile time division by zero erroneously
    Classification: Unclassified
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: joseph.h.garvin@gmail.com


Test case:

template<std::size_t x>
struct test {
  static const std::size_t a_
  =3D x ? 10 / x : 10;
};

Output from compiling:

alignptrtest.cpp: In instantiation of =E2=80=98const size_t test<0ul>::a_=
=E2=80=99:
alignptrtest.cpp:11:   instantiated from here
alignptrtest.cpp:6: warning: division by zero

The warning should be suppressed when zero is explicitly checked for. At
runtime this could require fancy analysis that might be unreasonable to exp=
ect,
but since this is compile time it should be possible to know whether the
division by 0 really occurs. Especially since it's smart enough to give the
warning even when dividing by (x+1-1).