[Bug libstdc++/56158] New: bad enum values computed by operator~ in ios_base.h

[richard-gccbugzilla at metafoo dot co.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56158



             Bug #: 56158

           Summary: bad enum values computed by operator~ in ios_base.h

    Classification: Unclassified

           Product: gcc

           Version: unknown

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: libstdc++

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: richard-gccbugzi...@metafoo.co.uk





The overloaded operator~s defined for the enumerations in ios_base.h have the

following form:



  Enum operator~(Enum e) { return Enum(~static_cast<int>(e)); }



The ~ creates values outside the range of values of the enumeration type, so

the cast back to the Enum type has an unspecified value (see

[expr.static.cast]p10), and in practice it produces an Enum value outside the

range of representable values for the Enum type, so behavior is undefined.



Fix:



--- include/bits/ios_base.h

+++ include/bits/ios_base.h

@@ -87,7 +87,7 @@



   inline _GLIBCXX_CONSTEXPR _Ios_Fmtflags

   operator~(_Ios_Fmtflags __a)

-  { return _Ios_Fmtflags(~static_cast<int>(__a)); }

+  { return _Ios_Fmtflags(static_cast<int>(__a) ^

static_cast<int>(_S_ios_fmtflags_end - 1)); }



   inline const _Ios_Fmtflags&

   operator|=(_Ios_Fmtflags& __a, _Ios_Fmtflags __b)

@@ -127,7 +127,7 @@



   inline _GLIBCXX_CONSTEXPR _Ios_Openmode

   operator~(_Ios_Openmode __a)

-  { return _Ios_Openmode(~static_cast<int>(__a)); }

+  { return _Ios_Openmode(static_cast<int>(__a) ^

static_cast<int>(_S_ios_openmode_end - 1)); }



   inline const _Ios_Openmode&

   operator|=(_Ios_Openmode& __a, _Ios_Openmode __b)

@@ -165,7 +165,7 @@



   inline _GLIBCXX_CONSTEXPR _Ios_Iostate

   operator~(_Ios_Iostate __a)

-  { return _Ios_Iostate(~static_cast<int>(__a)); }

+  { return _Ios_Iostate(static_cast<int>(__a) ^

static_cast<int>(_S_ios_iostate_end - 1)); }



   inline const _Ios_Iostate&

   operator|=(_Ios_Iostate& __a, _Ios_Iostate __b)