diff --git a/src/multibyte/internal.c b/src/multibyte/internal.c
index e9b938dd9f2ee2e65fcb264a2aa739c98f950997..11b9818fc479e6c7148ab3ced563233352f04ce8 100644
--- a/src/multibyte/internal.c
+++ b/src/multibyte/internal.c
@@ -15,27 +15,6 @@
                  R(0x80,0xc0) ) \
              | ( R(0x80,0xc0) >> 6 ) \
              | x )
-#ifdef I_FAILED_TO_RTFM_RFC3629
-#define F0(x) (( x==0 ? R(0x90,0xc0) : \
-                 R(0x80,0xc0) ) \
-             | ( R(0x80,0xc0) >> 6 ) \
-             | ( R(0x80,0xc0) >> 12 ) \
-             | x )
-#define F8(x) (( x==0 ? R(0xa0,0xc0) : \
-                 R(0x80,0xc0) ) \
-             | ( R(0x80,0xc0) >> 6 ) \
-             | ( R(0x80,0xc0) >> 12 ) \
-             | ( R(0x80,0xc0) >> 18 ) \
-             | x )
-#define FC(x) (( x==0 ? R(0x88,0xc0) : \
-                 R(0x80,0xc0) ) \
-             | ( R(0x80,0xc0) >> 6 ) \
-             | ( R(0x80,0xc0) >> 12 ) \
-             | ( R(0x80,0xc0) >> 18 ) \
-             | ( R(0x80,0xc0) >> 24 ) \
-             | x )
-#define F(x) ( x<8 ? F0(x) : x<12 ? F8((x&3)) : x<14 ? FC((x&1)) : -1 )
-#else
 #define F(x) ( ( x>=5 ? 0 : \
                  x==0 ? R(0x90,0xc0) : \
                  x==4 ? R(0x80,0xa0) : \
@@ -43,7 +22,6 @@
              | ( R(0x80,0xc0) >> 6 ) \
              | ( R(0x80,0xc0) >> 12 ) \
              | x )
-#endif
 
 const uint32_t bittab[] = {
 	              C(0x2),C(0x3),C(0x4),C(0x5),C(0x6),C(0x7),
@@ -52,9 +30,5 @@ const uint32_t bittab[] = {
 	D(0x8),D(0x9),D(0xa),D(0xb),D(0xc),D(0xd),D(0xe),D(0xf),
 	E(0x0),E(0x1),E(0x2),E(0x3),E(0x4),E(0x5),E(0x6),E(0x7),
 	E(0x8),E(0x9),E(0xa),E(0xb),E(0xc),E(0xd),E(0xe),E(0xf),
-	F(0x0),F(0x1),F(0x2),F(0x3),F(0x4),
-#ifdef I_FAILED_TO_RTFM_RFC3629
-	                                   F(0x5),F(0x6),F(0x7),
-	F(0x8),F(0x9),F(0xa),F(0xb),F(0xc),F(0xd)
-#endif
+	F(0x0),F(0x1),F(0x2),F(0x3),F(0x4)
 };
diff --git a/src/multibyte/internal.h b/src/multibyte/internal.h
index ec52bdfad268ce3ea56c1bd405fba5fba20b6076..df47331e11b215db6b67cef434a24c3be7702d2d 100644
--- a/src/multibyte/internal.h
+++ b/src/multibyte/internal.h
@@ -4,45 +4,13 @@
  * unnecessary.
  */
 
-#define LIBC
-#ifndef LIBC
-/* rename functions not to conflict with libc */
-#ifndef myprefix
-#define myprefix fsmu8_
-#endif
-#define concat2(a,b) a ## b
-#define concat(a,b) concat2(a,b)
-#define prefix(b) concat(myprefix,b)
-
-#undef mblen
-#undef mbrlen
-#undef mbrtowc
-#undef mbsinit
-#undef mbsnrtowcs
-#undef mbsrtowcs
-#undef wcrtomb
-#undef wcsrtombs
-#undef wcstombs
-#undef wctomb
-#define mblen prefix(mblen)
-#define mbrlen prefix(mbrlen)
-#define mbrtowc prefix(mbrtowc)
-#define mbsinit prefix(mbsinit)
-#define mbsnrtowcs prefix(mbsnrtowcs)
-#define mbsrtowcs prefix(mbsrtowcs)
-#define mbstowcs prefix(mbstowcs)
-#define wcrtomb prefix(wcrtomb)
-#define wcsnrtombs prefix(wcsnrtombs)
-#define wcsrtombs prefix(wcsrtombs)
-#define wcstombs prefix(wcstombs)
-#define wctomb prefix(wctomb)
-
-#define bittab prefix(bittab)
-#else
 #define bittab __fsmu8
-#endif
 
+#if 100*__GNUC__+__GNUC_MINOR__ >= 303 || defined(__PCC__) || defined(__TINYC__)
+extern const uint32_t bittab[] __attribute__((visibility("hidden")));
+#else
 extern const uint32_t bittab[];
+#endif
 
 /* Upper 6 state bits are a negative integer offset to bound-check next byte */
 /*    equivalent to: ( (b-0x80) | (b+offset) ) & ~0x3f      */
@@ -52,10 +20,5 @@ extern const uint32_t bittab[];
 #define R(a,b) ((uint32_t)((a==0x80 ? 0x40-b : -a) << 23))
 #define FAILSTATE R(0x80,0x80)
 
-#ifdef I_FAILED_TO_RTFM_RFC3629
-#define SA 0xc2u
-#define SB 0xfeu
-#else
 #define SA 0xc2u
 #define SB 0xf5u
-#endif
diff --git a/src/multibyte/mbsrtowcs.c b/src/multibyte/mbsrtowcs.c
index 64399cf2896d6e0cd0f53d86d8060b5ee5eac874..ebf0d6c9711c261726f77172ee68ce0df5263cb8 100644
--- a/src/multibyte/mbsrtowcs.c
+++ b/src/multibyte/mbsrtowcs.c
@@ -42,12 +42,6 @@ size_t mbsrtowcs(wchar_t *ws, const char **src, size_t wn, mbstate_t *st)
 resume0:
 			if (OOB(c,*s)) goto ilseq2; s++;
 			c <<= 6; if (!(c&(1U<<31))) break;
-#ifdef I_FAILED_TO_RTFM_RFC3629
-			if (*s++-0x80u >= 0x40) goto ilseq2;
-			c <<= 6; if (!(c&(1U<<31))) break;
-			if (*s++-0x80u >= 0x40) goto ilseq2;
-			c <<= 6; if (!(c&(1U<<31))) break;
-#endif
 			if (*s++-0x80u >= 0x40) goto ilseq2;
 			c <<= 6; if (!(c&(1U<<31))) break;
 			if (*s++-0x80u >= 0x40) goto ilseq2;
@@ -89,16 +83,6 @@ resume:
 			c = (c<<6) | *s++-0x80;
 			if (!(c&(1U<<31))) break;
 
-#ifdef I_FAILED_TO_RTFM_RFC3629
-			if (*s-0x80u >= 0x40) goto ilseq;
-			c = (c<<6) | *s++-0x80;
-			if (!(c&(1U<<31))) break;
-
-			if (*s-0x80u >= 0x40) goto ilseq;
-			c = (c<<6) | *s++-0x80;
-			if (!(c&(1U<<31))) break;
-#endif
-
 			if (*s-0x80u >= 0x40) goto ilseq;
 			c = (c<<6) | *s++-0x80;
 			if (!(c&(1U<<31))) break;