Configuration of glibmm defines many preprocessor constants in glibmmconfig.h.
Some of these are obsolete, and IMO should be removed. Similar constants have
been removed from libsigc++3.

I have examined the use in glibmm, atkmm, pangomm, gtkmm, gtkmm-documentation
and libxml++, git master branches.

M4 macros called from glibmm/configure.ac:

File       M4 macro, #define constant
----       --------------------------
c_std.m4   GLIBMM_C_STD_TIME_T_IS_NOT_INT32
             #define GLIBMM_HAVE_C_STD_TIME_T_IS_NOT_INT32
           Not used in glibmm, gtkmm

cxx.m4     GLIBMM_CXX_MEMBER_FUNCTIONS_MEMBER_TEMPLATES
             #define GLIBMM_MEMBER_FUNCTIONS_MEMBER_TEMPLATES
           Not used in glibmm, gtkmm

           GLIBMM_CXX_CAN_DISAMBIGUATE_CONST_TEMPLATE_SPECIALIZATIONS
             #define GLIBMM_HAVE_DISAMBIGUOUS_CONST_TEMPLATE_SPECIALIZATIONS
           Not used in gtkmm
           *** Used in glibmm

           GLIBMM_CXX_CAN_USE_DYNAMIC_CAST_IN_UNUSED_TEMPLATE_WITHOUT_DEFINITION
             #define
               GLIBMM_CAN_USE_DYNAMIC_CAST_IN_UNUSED_TEMPLATE_WITHOUT_DEFINITION
           Not used in gtkmm
           *** Used in glibmm

           GLIBMM_CXX_CAN_ASSIGN_NON_EXTERN_C_FUNCTIONS_TO_EXTERN_C_CALLBACKS
             #define
               GLIBMM_CAN_ASSIGN_NON_EXTERN_C_FUNCTIONS_TO_EXTERN_C_CALLBACKS
           Not used in glibmm, gtkmm

           GLIBMM_CXX_CAN_USE_NAMESPACES_INSIDE_EXTERNC
             #define GLIBMM_CAN_USE_NAMESPACES_INSIDE_EXTERNC
           Not used in glibmm, gtkmm

           GLIBMM_CXX_CAN_USE_THREAD_LOCAL
             #define GLIBMM_CAN_USE_THREAD_LOCAL
           Not used in glibmm, gtkmm

cxx_std.m4 GLIBMM_CXX_HAS_STD_ITERATOR_TRAITS
             #define GLIBMM_HAVE_STD_ITERATOR_TRAITS
           Not used in gtkmm
           *** Used in glibmm

           GLIBMM_CXX_HAS_SUN_REVERSE_ITERATOR 
             #define GLIBMM_HAVE_SUN_REVERSE_ITERATOR
           *** Used in glibmm, gtkmm

           GLIBMM_CXX_HAS_TEMPLATE_SEQUENCE_CTORS
             #define GLIBMM_HAVE_TEMPLATE_SEQUENCE_CTORS
           Not used in gtkmm
           *** Used in glibmm

           GLIBMM_CXX_ALLOWS_STATIC_INLINE_NPOS
             #define GLIBMM_HAVE_ALLOWS_STATIC_INLINE_NPOS
           Not used in gtkmm
           *** Used in glibmm

           GLIBMM_CXX_HAS_NAMESPACE_STD
             #define GLIBMM_HAVE_NAMESPACE_STD
           Called indirectly, via other m4 macros in cxx_std.m4.
           Not used in glibmm, gtkmm

debug.m4   GLIBMM_ARG_ENABLE_DEBUG_REFCOUNTING
             #define GLIBMM_DEBUG_REFCOUNTING
           *** Used in glibmm, gtkmm

sun.m4     GLIBMM_PROG_CXX_SUN
             #define GLIBMM_COMPILER_SUN_FORTE
           Not used in glibmm, gtkmm

None of these #define constants are used in atkmm, pangomm, libxml++ or
gtkmm-documentation.

7 out of these 14 #define constants are not used in glibmm or gtkmm.

  GLIBMM_EXCEPTIONS_ENABLED,
  GLIBMM_PROPERTIES_ENABLED,
  GLIBMM_VFUNCS_ENABLED and
  GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
are always defined. Can they be removed? Only GLIBMM_EXCEPTIONS_ENABLED is used
in any of the examined modules. It's only used in pangomm/pango/src/fontset.ccg,
and it should be removed from there.


glibmm/glib/glibmmconfig.h.in contains
  /* Dummy macro definition for compatibility with old code that expects
   * it to be defined.  Remove after grace period. */
  #define GLIBMM_USING_STD(Symbol)
Has the grace period ended?
GLIBMM_USING_STD is not used in any of the examined modules.