Use different scheme to handle MSVC6

Recent commit 0b08cab0fc46a5f381ca18a451f55cf12c81d966 caused a function
to not be compiled when running on MSVC6, and hence its callers needed
to use an alternative mechanism there.  This is easy enough, it turns
out, but it also turns out that there are more opportunities to call
this function.  Rather than having each caller have to know about the
MSVC6 problem, this current commit reimplements the function on that
platform to use a slow, dumb method, so knowing about the issue is
confined to just this one function.

5 files changed, 31 insertions, 20 deletions

diff --git a/embed.fnc b/embed.fnc
index 35202e8d7c..fadd45bca9 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -806,7 +806,7 @@ AndmoR	|bool	|is_utf8_invariant_string|NN const U8* const s		    \
 AnidR	|bool	|is_utf8_invariant_string_loc|NN const U8* const s	    \
 		|STRLEN len						    \
 		|NULLOK const U8 ** ep
-#if ! defined(EBCDIC) && ! defined USING_MSVC6
+#ifndef EBCDIC
 AniR	|unsigned int|_variant_byte_number|PERL_UINTMAX_T word
 #endif
 #if defined(PERL_CORE) || defined(PERL_EXT)
diff --git a/embed.h b/embed.h
index 334c6063fb..c633b57ca5 100644
--- a/embed.h
+++ b/embed.h
@@ -768,15 +768,15 @@
 #define whichsig_sv(a)		Perl_whichsig_sv(aTHX_ a)
 #define wrap_keyword_plugin(a,b)	Perl_wrap_keyword_plugin(aTHX_ a,b)
 #define wrap_op_checker(a,b,c)	Perl_wrap_op_checker(aTHX_ a,b,c)
-#if ! defined(EBCDIC) && ! defined USING_MSVC6
-#define _variant_byte_number	S__variant_byte_number
-#endif
 #if !(defined(HAS_MEMMEM))
 #define ninstr			Perl_ninstr
 #endif
 #if !(defined(HAS_SIGACTION) && defined(SA_SIGINFO))
 #define csighandler		Perl_csighandler
 #endif
+#if !defined(EBCDIC)
+#define _variant_byte_number	S__variant_byte_number
+#endif
 #if !defined(HAS_TRUNCATE) && !defined(HAS_CHSIZE) && defined(F_FREESP)
 #define my_chsize(a,b)		Perl_my_chsize(aTHX_ a,b)
 #endif
diff --git a/inline.h b/inline.h
index 769e0532ac..21151e36c7 100644
--- a/inline.h
+++ b/inline.h
@@ -401,8 +401,6 @@ S_is_utf8_invariant_string_loc(const U8* const s, STRLEN len, const U8 ** ep)
                                       | ( ( (PTR2nat(x)                       \
                                            & PERL_WORD_BOUNDARY_MASK) >> 2))))
 
-#  ifndef USING_MSVC6
-
     /* Do the word-at-a-time iff there is at least one usable full word.  That
      * means that after advancing to a word boundary, there still is at least a
      * full word left.  The number of bytes needed to advance is 'wordsize -
@@ -460,7 +458,6 @@ S_is_utf8_invariant_string_loc(const U8* const s, STRLEN len, const U8 ** ep)
         } while (x + PERL_WORDSIZE <= send);
     }
 
-#  endif    /* End of ! MSVC6 */
 #endif      /* End of ! EBCDIC */
 
     /* Process per-byte */
@@ -479,10 +476,7 @@ S_is_utf8_invariant_string_loc(const U8* const s, STRLEN len, const U8 ** ep)
     return TRUE;
 }
 
-#if ! defined(EBCDIC) && ! defined(USING_MSVC6)
-
-/* Apparent compiler error with MSVC6, so can't use this function.  All callers
- * to it must be compiled to use the EBCDIC fallback on MSVC6 */
+#ifndef EBCDIC
 
 PERL_STATIC_INLINE unsigned int
 S__variant_byte_number(PERL_UINTMAX_T word)
@@ -496,7 +490,24 @@ S__variant_byte_number(PERL_UINTMAX_T word)
     /* Get just the msb bits of each byte */
     word &= PERL_VARIANTS_WORD_MASK;
 
-#  if BYTEORDER == 0x1234 || BYTEORDER == 0x12345678
+#  ifdef USING_MSVC6    /* VC6 has some issues with the normal code, and the
+                           easiest thing is to hide that from the callers */
+    {
+        unsigned int i;
+        const U8 * s = (U8 *) &word;
+        dTHX;
+
+        for (i = 0; i < sizeof(word); i++ ) {
+            if (s[i]) {
+                return i;
+            }
+        }
+
+        Perl_croak(aTHX_ "panic: %s: %d: unexpected zero word\n",
+                                 __FILE__, __LINE__);
+    }
+
+#  elif BYTEORDER == 0x1234 || BYTEORDER == 0x12345678
 
     /* Bytes are stored like
      *  Byte8 ... Byte2 Byte1
diff --git a/proto.h b/proto.h
index eadfc976db..61a4db87b9 100644
--- a/proto.h
+++ b/proto.h
@@ -3806,13 +3806,6 @@ PERL_CALLCONV int	Perl_yylex(pTHX);
 PERL_CALLCONV int	Perl_yyparse(pTHX_ int gramtype);
 PERL_CALLCONV void	Perl_yyquit(pTHX);
 PERL_CALLCONV void	Perl_yyunlex(pTHX);
-#if ! defined(EBCDIC) && ! defined USING_MSVC6
-#ifndef PERL_NO_INLINE_FUNCTIONS
-PERL_STATIC_INLINE unsigned int	S__variant_byte_number(PERL_UINTMAX_T word)
-			__attribute__warn_unused_result__;
-#endif
-
-#endif
 #if ! defined(HAS_MEMRCHR) && (defined(PERL_CORE) || defined(PERL_EXT))
 #ifndef PERL_NO_INLINE_FUNCTIONS
 PERL_STATIC_INLINE void *	S_my_memrchr(const char * s, const char c, const STRLEN len);
@@ -3868,6 +3861,13 @@ PERL_CALLCONV_NO_RET int	Perl_magic_regdatum_set(pTHX_ SV* sv, MAGIC* mg)
 	assert(sv); assert(mg)
 
 #endif
+#if !defined(EBCDIC)
+#ifndef PERL_NO_INLINE_FUNCTIONS
+PERL_STATIC_INLINE unsigned int	S__variant_byte_number(PERL_UINTMAX_T word)
+			__attribute__warn_unused_result__;
+#endif
+
+#endif
 #if !defined(HAS_GETENV_LEN)
 PERL_CALLCONV char*	Perl_getenv_len(pTHX_ const char *env_elem, unsigned long *len);
 #define PERL_ARGS_ASSERT_GETENV_LEN	\
diff --git a/regexec.c b/regexec.c
index 530f1d6250..5a1c5ef61f 100644
--- a/regexec.c
+++ b/regexec.c
@@ -560,7 +560,7 @@ S_find_next_ascii(char * s, const char * send, const bool utf8_target)
 
     PERL_ARGS_ASSERT_FIND_NEXT_ASCII;
 
-#if ! defined(EBCDIC) && ! defined(USING_MSVC6)
+#ifndef EBCDIC
 
     if ((STRLEN) (send - s) >= PERL_WORDSIZE