inline.h: Add 'const's; avoid hiding outer variable

This changes some formal parameters to be const, and avoids reusing the
same variable name within an inner block, to avoid confusion

Author: khwilliamson

embed.fnc

@@ -741,9 +741,9 @@ AmnpdRP	|bool	|is_ascii_string|NN const U8* const s|const STRLEN len
 AmnpdRP	|bool	|is_invariant_string|NN const U8* const s|const STRLEN len
 AnpdD	|STRLEN	|is_utf8_char	|NN const U8 *s
 Abmnpd	|STRLEN	|is_utf8_char_buf|NN const U8 *buf|NN const U8 *buf_end
-AnipdP	|bool	|is_utf8_string	|NN const U8 *s|STRLEN len
-Anpdmb	|bool	|is_utf8_string_loc|NN const U8 *s|STRLEN len|NN const U8 **ep
-Anipd	|bool	|is_utf8_string_loclen|NN const U8 *s|STRLEN len|NULLOK const U8 **ep|NULLOK STRLEN *el
+AnipdP	|bool	|is_utf8_string	|NN const U8 *s|const STRLEN len
+Anpdmb	|bool	|is_utf8_string_loc|NN const U8 *s|const STRLEN len|NN const U8 **ep
+Anipd	|bool	|is_utf8_string_loclen|NN const U8 *s|const STRLEN len|NULLOK const U8 **ep|NULLOK STRLEN *el
 AmndP	|bool	|is_utf8_valid_partial_char				    \
 		|NN const U8 * const s|NN const U8 * const e
 AnidP	|bool	|is_utf8_valid_partial_char_flags			    \

inline.h

@@ -290,7 +290,7 @@ non-Unicode code points are allowed.
 PERL_STATIC_INLINE UV
 Perl_valid_utf8_to_uvchr(const U8 *s, STRLEN *retlen)
 {
-    UV expectlen = UTF8SKIP(s);
+    const UV expectlen = UTF8SKIP(s);
     const U8* send = s + expectlen;
     UV uv = *s;
 
@@ -373,7 +373,7 @@ L</is_utf8_string_loc>().
 */
 
 PERL_STATIC_INLINE bool
-Perl_is_utf8_string(const U8 *s, STRLEN len)
+Perl_is_utf8_string(const U8 *s, const STRLEN len)
 {
     /* This is now marked pure in embed.fnc, because isUTF8_CHAR now is pure.
      * Be aware of possible changes to that */
@@ -384,11 +384,11 @@ Perl_is_utf8_string(const U8 *s, STRLEN len)
     PERL_ARGS_ASSERT_IS_UTF8_STRING;
 
     while (x < send) {
-        STRLEN len = isUTF8_CHAR(x, send);
-        if (UNLIKELY(! len)) {
+        const STRLEN cur_len = isUTF8_CHAR(x, send);
+        if (UNLIKELY(! cur_len)) {
             return FALSE;
         }
-        x += len;
+        x += cur_len;
     }
 
     return TRUE;
@@ -418,7 +418,7 @@ See also L</is_utf8_string_loc>() and L</is_utf8_string>().
 */
 
 PERL_STATIC_INLINE bool
-Perl_is_utf8_string_loclen(const U8 *s, STRLEN len, const U8 **ep, STRLEN *el)
+Perl_is_utf8_string_loclen(const U8 *s, const STRLEN len, const U8 **ep, STRLEN *el)
 {
     const U8* const send = s + (len ? len : strlen((const char *)s));
     const U8* x = s;
@@ -427,11 +427,11 @@ Perl_is_utf8_string_loclen(const U8 *s, STRLEN len, const U8 **ep, STRLEN *el)
     PERL_ARGS_ASSERT_IS_UTF8_STRING_LOCLEN;
 
     while (x < send) {
-        STRLEN len = isUTF8_CHAR(x, send);
-        if (UNLIKELY(! len)) {
+        const STRLEN cur_len = isUTF8_CHAR(x, send);
+        if (UNLIKELY(! cur_len)) {
             break;
         }
-        x += len;
+        x += cur_len;
         outlen++;
     }
 

proto.h

@@ -1609,17 +1609,17 @@ PERL_CALLCONV bool	Perl_is_utf8_space(pTHX_ const U8 *p)
 #define PERL_ARGS_ASSERT_IS_UTF8_SPACE	\
 	assert(p)
 
-PERL_STATIC_INLINE bool	Perl_is_utf8_string(const U8 *s, STRLEN len)
+PERL_STATIC_INLINE bool	Perl_is_utf8_string(const U8 *s, const STRLEN len)
 			__attribute__pure__;
 #define PERL_ARGS_ASSERT_IS_UTF8_STRING	\
 	assert(s)
 
 #ifndef NO_MATHOMS
-PERL_CALLCONV bool	Perl_is_utf8_string_loc(const U8 *s, STRLEN len, const U8 **ep);
+PERL_CALLCONV bool	Perl_is_utf8_string_loc(const U8 *s, const STRLEN len, const U8 **ep);
 #define PERL_ARGS_ASSERT_IS_UTF8_STRING_LOC	\
 	assert(s); assert(ep)
 #endif
-PERL_STATIC_INLINE bool	Perl_is_utf8_string_loclen(const U8 *s, STRLEN len, const U8 **ep, STRLEN *el);
+PERL_STATIC_INLINE bool	Perl_is_utf8_string_loclen(const U8 *s, const STRLEN len, const U8 **ep, STRLEN *el);
 #define PERL_ARGS_ASSERT_IS_UTF8_STRING_LOCLEN	\
 	assert(s)
 PERL_CALLCONV bool	Perl_is_utf8_upper(pTHX_ const U8 *p)