https://trac.macports.org/ticket/34639
https://bugs.gentoo.org/show_bug.cgi?id=491098

--- work/gcc-5666.3/gcc/toplev.h
+++ work/gcc-5666.3/gcc/toplev.h
@@ -151,6 +151,8 @@
 /* Return true iff flags are set as if -ffast-math.  */
 extern bool fast_math_flags_set_p	(void);
 
+#if GCC_VERSION < 3004
+
 /* Return log2, or -1 if not exact.  */
 extern int exact_log2                  (unsigned HOST_WIDE_INT);
 
@@ -158,7 +160,7 @@
 extern int floor_log2                  (unsigned HOST_WIDE_INT);
 
 /* Inline versions of the above for speed.  */
-#if GCC_VERSION >= 3004
+#else /* GCC_VERSION < 3004 */
 # if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG
 #  define CLZ_HWI __builtin_clzl
 #  define CTZ_HWI __builtin_ctzl
@@ -172,18 +172,18 @@
 #  define CTZ_HWI __builtin_ctz
 # endif
 
-extern inline int
+static inline int
 floor_log2 (unsigned HOST_WIDE_INT x)
 {
   return x ? HOST_BITS_PER_WIDE_INT - 1 - (int) CLZ_HWI (x) : -1;
 }
 
-extern inline int
+static inline int
 exact_log2 (unsigned HOST_WIDE_INT x)
 {
   return x == (x & -x) && x ? (int) CTZ_HWI (x) : -1;
 }
-#endif /* GCC_VERSION >= 3004 */
+#endif /* GCC_VERSION < 3004 */
 
 /* Functions used to get and set GCC's notion of in what directory
    compilation was started.  */
--- work/gcc-5666.3/gcc/toplev.c
+++ work/gcc-5666.3/gcc/toplev.c
@@ -555,7 +555,7 @@
    for floor_log2 and exact_log2; see toplev.h.  That construct, however,
    conflicts with the ISO C++ One Definition Rule.   */
 
-#if GCC_VERSION < 3004 || !defined (__cplusplus)
+#if GCC_VERSION < 3004
 
 /* Given X, an unsigned number, return the largest int Y such that 2**Y <= X.
    If X is 0, return -1.  */
@@ -607,7 +607,7 @@
 #endif
 }
 
-#endif /*  GCC_VERSION < 3004 || !defined (__cplusplus)  */
+#endif /*  GCC_VERSION < 3004 */
 
 /* Handler for fatal signals, such as SIGSEGV.  These are transformed
    into ICE messages, which is much more user friendly.  In case the