diff --git a/cxx/ismpf.cc b/cxx/ismpf.cc
index e5f8bb8b..99cf5afa 100644
--- a/cxx/ismpf.cc
+++ b/cxx/ismpf.cc
@@ -50,7 +50,7 @@ operator>> (istream &i, mpf_ptr f)
   const char *lconv_point = localeconv()->decimal_point;
 
   // C++ decimal point
-#if HAVE_STD__LOCALE && defined (__GNUC__)
+#if HAVE_STD__LOCALE && !defined (__sun)
   const locale& loc = i.getloc();
   char point_char = use_facet< numpunct<char> >(loc).decimal_point();
 #else
@@ -63,7 +63,7 @@ operator>> (istream &i, mpf_ptr f)
   if (i.flags() & ios::skipws) // skip initial whitespace
     {
       // C++ isspace
-#if HAVE_STD__LOCALE && defined(__GNUC__)
+#if HAVE_STD__LOCALE && !defined(__sun)
       const ctype<char>& ct = use_facet< ctype<char> >(loc);
 #define cxx_isspace(c)  (ct.is(ctype_base::space,(c)))
 #else
diff --git a/cxx/ismpz.cc b/cxx/ismpz.cc
index 1c1414fc..a4ba3fa2 100644
--- a/cxx/ismpz.cc
+++ b/cxx/ismpz.cc
@@ -39,7 +39,7 @@ operator>> (istream &i, mpz_ptr z)
 
   if (i.flags() & ios::skipws) // skip initial whitespace
     {
-#if HAVE_STD__LOCALE && defined (__GNUC__)
+#if HAVE_STD__LOCALE && !defined (__sun)
       const ctype<char>& ct = use_facet< ctype<char> >(i.getloc());
 #define cxx_isspace(c)  (ct.is(ctype_base::space,(c)))
 #else
diff --git a/cxx/osmpf.cc b/cxx/osmpf.cc
index e4660181..f63fd672 100644
--- a/cxx/osmpf.cc
+++ b/cxx/osmpf.cc
@@ -44,7 +44,7 @@ operator<< (ostream &o, mpf_srcptr f)
 
   __gmp_doprnt_params_from_ios (&param, o);
 
-#if HAVE_STD__LOCALE && defined (__GNUC__)
+#if HAVE_STD__LOCALE && !defined (__sun)
   char  point[2];
   point[0] = use_facet< numpunct<char> >(o.getloc()).decimal_point();
   point[1] = '\0';
diff --git a/gmp-impl.h b/gmp-impl.h
index 26fd59a2..aa1cd611 100644
--- a/gmp-impl.h
+++ b/gmp-impl.h
@@ -218,13 +218,13 @@ typedef unsigned long       gmp_uint_least32_t;
    is more restrictive than "pure".  See info node "(gcc)Function
    Attributes".  __GMP_NO_ATTRIBUTE_CONST_PURE lets tune/common.c etc turn
    this off when trying to write timing loops.  */
-#if HAVE_ATTRIBUTE_CONST && ! defined (__GMP_NO_ATTRIBUTE_CONST_PURE) && defined (__GNUC__)
+#if HAVE_ATTRIBUTE_CONST && ! defined (__GMP_NO_ATTRIBUTE_CONST_PURE) && !( defined (__cplusplus) && defined (__sun))
 #define ATTRIBUTE_CONST  __attribute__ ((const))
 #else
 #define ATTRIBUTE_CONST
 #endif
 
-#if HAVE_ATTRIBUTE_NORETURN && defined (__GNUC__)
+#if HAVE_ATTRIBUTE_NORETURN && !( defined (__cplusplus) && defined (__sun))
 #define ATTRIBUTE_NORETURN  __attribute__ ((noreturn))
 #else
 #define ATTRIBUTE_NORETURN
@@ -232,7 +232,7 @@ typedef unsigned long       gmp_uint_least32_t;
 
 /* "malloc" means a function behaves like malloc in that the pointer it
    returns doesn't alias anything.  */
-#if HAVE_ATTRIBUTE_MALLOC && defined (__GNUC__)
+#if HAVE_ATTRIBUTE_MALLOC && !( defined (__cplusplus) && defined (__sun))
 #define ATTRIBUTE_MALLOC  __attribute__ ((malloc))
 #else
 #define ATTRIBUTE_MALLOC