Fix Issue #17372 - Deal with NOTHING regops in trie code properly

We weren't handling NOTHING regops that were not followed
by a trieable type in the trie code.

Author: demerphq

regcomp.c

@@ -2797,7 +2797,12 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
         if (OP(noper) == NOTHING) {
             /* skip past a NOTHING at the start of an alternation
              * eg, /(?:)a|(?:b)/ should be the same as /a|b/
+             *
+             * If the next node is not something we are supposed to process
+             * we will just ignore it due to the condition guarding the
+             * next block.
              */
+
             regnode *noper_next= regnext(noper);
             if (noper_next < tail)
                 noper= noper_next;
@@ -3019,6 +3024,9 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                 regnode *noper_next= regnext(noper);
                 if (noper_next < tail)
                     noper= noper_next;
+                /* we will undo this assignment if noper does not
+                 * point at a trieable type in the else clause of
+                 * the following statement. */
             }
 
             if (    noper < tail
@@ -3080,7 +3088,13 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                         Perl_croak( aTHX_ "panic! In trie construction, no char mapping for %" IVdf, uvc );
 		    }
 		}
-	    }
+            } else {
+                /* If we end up here it is because we skipped past a NOTHING, but did not end up
+                 * on a trieable type. So we need to reset noper back to point at the first regop
+                 * in the branch before we call TRIE_HANDLE_WORD()
+                */
+                noper= NEXTOPER(cur);
+            }
             TRIE_HANDLE_WORD(state);
 
         } /* end second pass */
@@ -3244,6 +3258,9 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                 regnode *noper_next= regnext(noper);
                 if (noper_next < tail)
                     noper= noper_next;
+                /* we will undo this assignment if noper does not
+                 * point at a trieable type in the else clause of
+                 * the following statement. */
             }
 
             if (    noper < tail
@@ -3284,6 +3301,12 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                     /* charid is now 0 if we dont know the char read, or
                      * nonzero if we do */
                 }
+            } else {
+                /* If we end up here it is because we skipped past a NOTHING, but did not end up
+                 * on a trieable type. So we need to reset noper back to point at the first regop
+                 * in the branch before we call TRIE_HANDLE_WORD().
+                */
+                noper= NEXTOPER(cur);
             }
             accept_state = TRIE_NODENUM( state );
             TRIE_HANDLE_WORD(accept_state);

t/re/re_tests

@@ -2017,6 +2017,7 @@ AB\s+\x{100}	AB \x{100}X	y	-	-
 /(?iu)(?<=\xdf)hbase/	sshbase	y	$&	hbase
 /\x{30c3}?[\x{30a2}\x{30a4}\x{30a6}\x{30a8}\x{30aa}-\x{30e2}\x{30e4}\x{30e6}\x{30e8}-\x{30f4}](?:[\x{30e3}\x{30e5}\x{30e7}\x{30a1}\x{30a3}\x{30a5}\x{30a7}\x{30a9}])?\x{30fc}?\x{30f3}?/	\x{30de}\x{30fc}\x{30af}\x{30b5}\x{30fc}\x{30d3}\x{30b9}	y	$&	\x{30de}\x{30fc}	# part of [perl #133942
 /[\x{3041}-\x{3093}]+/	\x{6f22}\x{5b57}\x{3001}\x{30ab}\x{30bf}\x{30ab}\x{30ca}\x{3001}\x{3072}\x{3089}\x{304c}\x{306a}\x{306e}\x{5165}\x{3063}\x{305f}String	y	$&	\x{3072}\x{3089}\x{304c}\x{306a}\x{306e}	# [perl #133978]
-
+/(?:0)|(?:)(?:[1-9])/	q0	y	$&	0	# [https://github.com/Perl/perl5/issues/17372]
 # Keep these lines at the end of the file
+# pat	string	y/n/etc	expr	expected-expr	skip-reason	comment
 # vim: softtabstop=0 noexpandtab