Add S_parse_ident_no_copy()

The way parse_ident() is structured, it uses filling the output buffer
to determine if an identifier has too many bytes in it.  It would be a
pain to restructure it to not do that.  So S_parse_ident_no_copy() is
created to wrap plain parse_ident(), so that callers that don't care
about getting the output buffer don't have to deal with it.

These parsing functions are cold code; there is no need to try to eke
out every bit of performance from them.

Author: khwilliamson

embed.fnc

@@ -6174,6 +6174,11 @@ S	|char * |parse_ident	|SPTR const char *s			\
 				|EPTR char * const e			\
 				|bool is_utf8				\
 				|U32 flags
+S	|char * |parse_ident_no_copy					\
+				|SPTR const char *s			\
+				|EPTR const char * const s_end		\
+				|bool is_utf8				\
+				|U32 flags
 S	|int	|pending_ident
 RS	|char * |scan_const	|NN char *start
 RS	|char * |scan_formline	|NN char *s

embed.h

@@ -1688,6 +1688,7 @@
 #     define lop(a,b,c,d)                       S_lop(aTHX_ a,b,c,d)
 #     define missingterm(a,b)                   S_missingterm(aTHX_ a,b)
 #     define parse_ident(a,b,c,d,e,f)           S_parse_ident(aTHX_ a,b,c,d,e,f)
+#     define parse_ident_no_copy(a,b,c,d)       S_parse_ident_no_copy(aTHX_ a,b,c,d)
 #     define pending_ident()                    S_pending_ident(aTHX)
 #     define scan_const(a)                      S_scan_const(aTHX_ a)
 #     define scan_formline(a)                   S_scan_formline(aTHX_ a)

proto.h

@@ -10471,6 +10471,22 @@ S_parse_ident(pTHX_ const char *s, const char * const s_end,
     croak("%s", ident_too_long);
 }
 
+PERL_STATIC_INLINE char *
+S_parse_ident_no_copy(pTHX_ const char *s, const char * const s_end,
+                      bool is_utf8, U32 flags)
+{
+    PERL_ARGS_ASSERT_PARSE_IDENT_NO_COPY;
+
+    /* This just wraps parse_ident for functions that call it and don't need
+     * the actual identifier string returned.  For example, they might just
+     * want to test if the input is valid. */
+
+    char scratch[ PERL_IDENTIFIER_LENGTH ];
+    char * dest = scratch;
+
+    return parse_ident(s, s_end, &dest, C_ARRAY_END(scratch), is_utf8, flags);
+}
+
 char *
 Perl_scan_word(pTHX_ char *s, char *dest, char * dest_end, int allow_package, STRLEN *slp)
 {