iostream gives error _LIBCPP_BEGIN_NAMESPACE_STD

hi,
am using keil mdk5.26 to build c and c++ files and when i enclude <iostream> in header files that contain classes and cpp features it gives me 19 error as followas:

*** Using Compiler 'V6.10.1', folder: 'C:\Keil_v5\ARM\ARMCLANG\Bin'
Build target 'Target 1'
Application/SysMng.c(4): warning: In file included from...
./decentlib/src\elkrem.h(13): warning: In file included from...
./decentlib/src/Arduhdlc.h(12): warning: In file included from...
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iostream(38): warning: In file included from...
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\ios(215): warning: In file included from...
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(96): error: unknown type name '_LIBCPP_BEGIN_NAMESPACE_STD'
_LIBCPP_BEGIN_NAMESPACE_STD
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(98): error: expected ';' after top level declarator
class _LIBCPP_TYPE_VIS ios_base; ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(100): error: unknown type name 'template'
template<class _CharT> struct _LIBCPP_TEMPLATE_VIS char_traits;
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(100): error: expected identifier or '('
template<class _CharT> struct _LIBCPP_TEMPLATE_VIS char_traits; ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(101): error: unknown type name 'template'
template<class _Tp> class _LIBCPP_TEMPLATE_VIS allocator;
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(101): error: expected identifier or '('
template<class _Tp> class _LIBCPP_TEMPLATE_VIS allocator; ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(103): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT> >
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(103): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT> > ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(106): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT> >
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(106): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT> > ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(108): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT> >
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(108): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT> > ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(110): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT> >
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(110): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT> > ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(112): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT> >
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(112): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT> > ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(115): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT>,
^ C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(115): error: expected identifier or '('
template <class _CharT, class _Traits = char_traits<_CharT>, ^
C:/Keil_v5/ARM/ARMCLANG/include/libcxx\iosfwd(118): error: unknown type name 'template'
template <class _CharT, class _Traits = char_traits<_CharT>,
^ fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
compiling SysMng.c...
".\Objects\ELKREM.axf" - 19 Error(s), 0 Warning(s).
Target not created.
Build Time Elapsed: 00:00:03

## what should i do