 __gnu_cxx | GNU extensions for public use |
  __detail | Implementation details not part of the namespace __gnu_cxx interface |
  typelist | GNU typelist extensions for public compile-time use |
 __gnu_debug | GNU debug classes for public use |
 __gnu_internal | GNU implemenation details, not for public use or export. Used only when anonymous namespaces cannot be substituted |
 __gnu_parallel | GNU parallel code for public use |
 __gnu_pbds | GNU extensions for policy-based data structures for public use |
 __gnu_profile | GNU profile code for public use |
 __gnu_sequential | GNU sequential classes for public use |
 abi | The cross-vendor C++ Application Binary Interface. A namespace alias to __cxxabiv1, but user programs should use the alias 'abi' |
 std | ISO C++ entities toplevel namespace is std |
  __debug | GNU debug code, replaces standard behavior with debug behavior |
  __detail | Implementation details not part of the namespace std interface |
  __parallel | GNU parallel code, replaces standard behavior with parallel behavior |
  __profile | GNU profile code, replaces standard behavior with profile behavior |
  chrono | ISO C++ 2011 entities sub-namespace for time and date |
  decimal | ISO/IEC TR 24733 Decimal floating-point arithmetic |
  placeholders | ISO C++11 entities sub-namespace for functional |
  regex_constants | ISO C++-0x entities sub namespace for regex |
  rel_ops | The generated relational operators are sequestered here |
  this_thread | ISO C++ 2011 entities sub-namespace for thread. 30.3.2 Namespace this_thread |
  tr1 | ISO C++ TR1 entities toplevel namespace is std::tr1 |
   __detail | Implementation details not part of the namespace std::tr1 interface |
  tr2 | ISO C++ TR2 entities toplevel namespace is std::tr2 |
   __detail | Implementation details not part of the namespace std::tr2 interface |