utf8_to_uv_msgs: Avoid extra deref pointer writes

This function is passed an address of where to write some values.
Instead of updating the derefernced pointer each time, do it once after
all the information is accumulated.

This allows for the values to be updated without updating the pointed to
variable, so makes some case in a switch() able to be more uniform.

Author: khwilliamson

utf8.c

@@ -1603,8 +1603,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
     UV uv;
     SSize_t expectlen;    /* How long should this sequence be? */
     SSize_t avail_len;    /* When input is too short, gives what that is */
-    U32 discard_errors;   /* Used to save branches when 'errors' is NULL; this
-                             gets set and discarded */
 
     dTHX;
 
@@ -1650,14 +1648,10 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
     possible_problems = 0;
     expectlen = 0;
     avail_len = 0;
-    discard_errors = 0;
 
     if (errors) {
         *errors = 0;
     }
-    else {
-        errors = &discard_errors;
-    }
 
     /* Accumulate the code point translation of the input byte sequence
      * s0 .. e-1, looking for malformations.
@@ -1986,6 +1980,7 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
 
         bool disallowed = FALSE;
         const U32 orig_problems = possible_problems;
+        U32 error_flags_return = 0;
 
         /* The following macro returns 0 if no message needs to be generated
          * for this problem even if everything else says to.  Otherwise returns
@@ -2034,6 +2029,11 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
 
             U32 this_flag_bit = this_problem;
 
+            /* All cases but these two set this; it makes the cases simpler
+             * to do it here */
+            error_flags_return |= this_problem & ~( UTF8_GOT_PERL_EXTENDED
+                                                   |UTF8_GOT_SUPER);
+
             /* Turn off so next iteration doesn't retry this */
             possible_problems &= ~this_problem;
 
@@ -2056,8 +2056,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 break;
 
               case UTF8_GOT_EMPTY:
-                *errors |= UTF8_GOT_EMPTY;
-
                 if (! (flags & UTF8_ALLOW_EMPTY)) {
 
                     /* This so-called malformation is now treated as a bug in
@@ -2075,8 +2073,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 break;
 
               case UTF8_GOT_CONTINUATION:
-                *errors |= UTF8_GOT_CONTINUATION;
-
                 if (! (flags & UTF8_ALLOW_CONTINUATION)) {
                     disallowed = TRUE;
                     if (NEED_MESSAGE(WARN_UTF8,,)) {
@@ -2091,7 +2087,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 break;
 
               case UTF8_GOT_SHORT:
-                *errors |= UTF8_GOT_SHORT;
                 uv = UNICODE_REPLACEMENT;
 
                 if (! (flags & UTF8_ALLOW_SHORT)) {
@@ -2110,7 +2105,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 break;
 
               case UTF8_GOT_NON_CONTINUATION:
-                *errors |= UTF8_GOT_NON_CONTINUATION;
                 uv = UNICODE_REPLACEMENT;
 
                 if (! (flags & UTF8_ALLOW_NON_CONTINUATION)) {
@@ -2140,8 +2134,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                  * this case are true */
 
                 if (flags & UTF8_WARN_SURROGATE) {
-                    *errors |= UTF8_GOT_SURROGATE;
-
                     if (NEED_MESSAGE(WARN_SURROGATE,,)) {
                         pack_warn = packWARN(WARN_SURROGATE);
 
@@ -2161,7 +2153,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
 
                 if (flags & UTF8_DISALLOW_SURROGATE) {
                     disallowed = TRUE;
-                    *errors |= UTF8_GOT_SURROGATE;
                 }
 
                 break;
@@ -2173,8 +2164,6 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                  * this case are true */
 
                 if (flags & UTF8_WARN_NONCHAR) {
-                    *errors |= UTF8_GOT_NONCHAR;
-
                     if (NEED_MESSAGE(WARN_NONCHAR,,)) {
                         /* The code above should have guaranteed that we don't
                          * get here with errors other than overlong */
@@ -2188,13 +2177,11 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
 
                 if (flags & UTF8_DISALLOW_NONCHAR) {
                     disallowed = TRUE;
-                    *errors |= UTF8_GOT_NONCHAR;
                 }
 
                 break;
 
               case UTF8_GOT_LONG:
-                *errors |= UTF8_GOT_LONG;
 
                 if (! (flags & UTF8_ALLOW_LONG_AND_ITS_VALUE)) {
                     uv = UNICODE_REPLACEMENT;
@@ -2256,17 +2243,16 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 /* Overflow means also got a super and are using Perl's
                  * extended UTF-8, but we handle all three cases here */
                 possible_problems &= ~(UTF8_GOT_SUPER|UTF8_GOT_PERL_EXTENDED);
-                *errors |= UTF8_GOT_OVERFLOW;
                 uv = UNICODE_REPLACEMENT;
 
                 /* But the API says we flag all errors found */
                 if (flags & (UTF8_WARN_SUPER|UTF8_DISALLOW_SUPER)) {
-                    *errors |= UTF8_GOT_SUPER;
+                    error_flags_return |= UTF8_GOT_SUPER;
                 }
                 if (flags
                         & (UTF8_WARN_PERL_EXTENDED|UTF8_DISALLOW_PERL_EXTENDED))
                 {
-                    *errors |= UTF8_GOT_PERL_EXTENDED;
+                    error_flags_return |= UTF8_GOT_PERL_EXTENDED;
                 }
 
                 /* Disallow if any of the three categories say to */
@@ -2312,7 +2298,7 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                  * warned about */
 
                 if (flags & UTF8_WARN_SUPER) {
-                    *errors |= UTF8_GOT_SUPER;
+                    error_flags_return |= UTF8_GOT_SUPER;
 
                     if (NEED_MESSAGE(WARN_NON_UNICODE,,)) {
                         pack_warn = packWARN(WARN_NON_UNICODE);
@@ -2365,7 +2351,7 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                     if (flags & ( UTF8_WARN_PERL_EXTENDED
                                  |UTF8_DISALLOW_PERL_EXTENDED))
                     {
-                        *errors |= UTF8_GOT_PERL_EXTENDED;
+                        error_flags_return |= UTF8_GOT_PERL_EXTENDED;
 
                         if (flags & UTF8_DISALLOW_PERL_EXTENDED) {
                             disallowed = TRUE;
@@ -2374,7 +2360,7 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
                 }
 
                 if (flags & UTF8_DISALLOW_SUPER) {
-                    *errors |= UTF8_GOT_SUPER;
+                    error_flags_return |= UTF8_GOT_SUPER;
                     disallowed = TRUE;
                 }
 
@@ -2409,6 +2395,10 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
             *advance_p = curlen;
         }
 
+        if (errors) {
+            *errors = error_flags_return;
+        }
+
         if (disallowed) {
             success = false;
             uv = UNICODE_REPLACEMENT;