locale.c: Don't do asymmetric back out on failure

This fixes #23519

When something goes wrong doing locale-aware string collation, the code
attempts to carry on as well as can be expected.  Prior to this commit
the backout code was asymmetric, trying to undo things that had not been
done.  This happened when the failure was early on.

In the case of this ticket, the platform has a defective locale that was
detectable before getting very far along.

The solution adopted here is to jump to a different label for those
early failures that does less backout than for later failures.

Author: khwilliamson

locale.c

@@ -9663,7 +9663,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
         if (PL_collxfrm_base != 0) { /* bad collation => skip */
             DEBUG_L(PerlIO_printf(Perl_debug_log,
                           "mem_collxfrm_: locale's collation is defective\n"));
-            goto bad;
+            goto bad_no_strxfrm;
         }
 
         /* (mult, base) == (0,0) means we need to calculate mult and base
@@ -9789,7 +9789,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
                 DEBUG_L(PerlIO_printf(Perl_debug_log,
                     "mem_collxfrm_: Couldn't find any character to replace"
                     " embedded NULs in locale %s with", PL_collation_name));
-                goto bad;
+                goto bad_no_strxfrm;
             }
 
             DEBUG_L(PerlIO_printf(Perl_debug_log,
@@ -9930,7 +9930,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
                         "mem_collxfrm_: Couldn't find any character to"
                         " replace above-Latin1 chars in locale %s with",
                         PL_collation_name));
-                    goto bad;
+                    goto bad_no_strxfrm;
                 }
 
                 DEBUG_L(PerlIO_printf(Perl_debug_log,
@@ -10090,7 +10090,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
     if (UNLIKELY(! xbuf)) {
         DEBUG_L(PerlIO_printf(Perl_debug_log,
                       "mem_collxfrm_: Couldn't malloc %zu bytes\n", xAlloc));
-        goto bad;
+        goto bad_no_strxfrm;
     }
 
     /* Store the collation id */
@@ -10119,7 +10119,6 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
         STMT_START {                                                    \
             if (constructed_locale != (locale_t) 0)                     \
                 freelocale(constructed_locale);                         \
-            CLEANUP_NON_STRXFRM;                                        \
         } STMT_END
 #  else
 #    define my_strxfrm(dest, src, n)  strxfrm(dest, src, n)
@@ -10128,12 +10127,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
     orig_CTYPE_locale = toggle_locale_c(LC_CTYPE, PL_collation_name);
 
 #      define CLEANUP_STRXFRM                                           \
-        STMT_START {                                                    \
-                restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_locale);  \
-                CLEANUP_NON_STRXFRM;                                    \
-        } STMT_END
-#    else
-#      define CLEANUP_STRXFRM  CLEANUP_NON_STRXFRM
+            restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_locale);
 #    endif
 #  endif
 
@@ -10275,6 +10269,7 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
 
     DEBUG_L(print_collxfrm_input_and_return(s, s + len, xbuf, *xlen, utf8));
     CLEANUP_STRXFRM;
+    CLEANUP_NON_STRXFRM;
 
     /* Free up unneeded space; retain enough for trailing NUL */
     Renew(xbuf, COLLXFRM_HDR_LEN + *xlen + 1, char);
@@ -10286,9 +10281,12 @@ Perl_mem_collxfrm_(pTHX_ const char *input_string,
     DEBUG_L(print_collxfrm_input_and_return(s, s + len, NULL, 0, utf8));
     CLEANUP_STRXFRM;
 
+  bad_no_strxfrm:   /* Found a problem before strxfrm() got called */
+    DEBUG_L(print_collxfrm_input_and_return(s, s + len, NULL, 0, utf8));
+
     Safefree(xbuf);
     *xlen = 0;
-
+    CLEANUP_NON_STRXFRM;
     return NULL;
 }