More refactoring: keep track of empty branches during compiling, replacing a

post-compile scan.

ChangeLog

@@ -237,6 +237,13 @@ be the result.
 the internal recursive calls that are used for lookrounds and recursions within 
 the pattern.
 
+37. More refactoring has got rid of the internal could_be_empty_branch()
+function (around 400 lines of code, including comments) by keeping track of
+could-be-emptiness as the pattern is compiled instead of scanning compiled 
+groups. (This would have been much harder before the refactoring of #3 above.)
+This lifts a restriction on the number of branches in a group (more than about 
+1100 would give "pattern is too complicated").
+
 
 Version 10.22 29-July-2016
 --------------------------

testdata/testinput2

@@ -4651,7 +4651,7 @@ B)x/alt_verbnames,mark
 
 /abcdef/hex,max_pattern_length=3
 
-# These two patterns used to take a long time to compile
+# These patterns used to take a long time to compile
 
 "(.*)
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
@@ -4664,9 +4664,6 @@ B)x/alt_verbnames,mark
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
 a)"xI
 
-# When (?| is used and groups of the same number may be different,
-# we have to rely on a count to catch overly complicated patterns.
-
 "(?|()|())(.*)
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
@@ -4941,4 +4938,10 @@ a)"xI
 
 "()X|((((((((()))))))((((())))))\2())((((((\2\2)))\2)(\22((((\2\2)2))\2)))(2\ZZZ)+:)Z^|91ZiZZnter(ZZ |91Z(ZZ ZZ(\r2Z( or#(\Z2(Z\Z(\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)2))\2Z+:)Z|91Z(ZZ ZZ(\r2Z( or#(\Z2(Z\Z((Z*(\2(Z\':))\0)i|||||||||||||||loZ\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)2))\2Z)))int \)\0nte!rnal errpr\2\\21r(2\ZZZ)+:)Z!|91Z(ZZ ZZ(\r2Z( or#(\Z2(Z\Z(\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)2))\2Z)))int \)\0(2\ZZZ)+:)Z^|91ZiZZnter(ZZ |91Z(ZZ ZZ(\r2Z( or#(\Z2(Z\Z(\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)2))\2Z)))int \)\0(2\ZZZ)+:)Z^)))int \)\0(2\ZZZ)+:)Z^|91ZiZZnter(ZZernZal ZZ(\r2Z( or#(\Z2(Z\Z(\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)2))\2Z)))int \))\ZZ(\r2Z( or#(\Z2(Z\Z(\2\2)2))\2Z)Z(\22Z((\Z2(Z\Z(\2\2)))\2))))((((((\2\2))))))"I
 
+# This checks that new code for handling groups that may match an empty string
+# works on a very large number of alternatives. This pattern used to provoke a 
+# complaint that it was too complicated.
+
+/(?:\[A|B|C|D|E|F|G|H|I|J|]{200}Z)/expand
+
 # End of testinput2 

testdata/testoutput2

@@ -10741,7 +10741,8 @@ Matched, but too many substrings
 
 /(?(DEFINE)(a(?2)|b)(b(?1)|a))(?:(?1)|(?2))/I
 Capturing subpattern count = 2
-Subject length lower bound = 1
+May match empty string
+Subject length lower bound = 0
 
 /(a(?2)|b)(b(?1)|a)(?:(?1)|(?2))/I
 Capturing subpattern count = 2
@@ -14759,7 +14760,7 @@ Failed: error 188 at offset 0: pattern string is longer than the limit set by th
 
 /abcdef/hex,max_pattern_length=3
 
-# These two patterns used to take a long time to compile
+# These patterns used to take a long time to compile
 
 "(.*)
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
@@ -14782,14 +14783,14 @@ May match empty string
 Options: extended
 Subject length lower bound = 0
 
-# When (?| is used and groups of the same number may be different,
-# we have to rely on a count to catch overly complicated patterns.
-
 "(?|()|())(.*)
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))"xI
-Failed: error 186 at offset 148: regular expression is too complicated
+Capturing subpattern count = 13
+May match empty string
+Options: extended
+Subject length lower bound = 0
 
 "(?|()|())(?<=a()
 ((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))((?-2)(?-2))
@@ -15417,6 +15418,12 @@ Max back reference = 22
 Contains explicit CR or LF match
 Subject length lower bound = 0
 
+# This checks that new code for handling groups that may match an empty string
+# works on a very large number of alternatives. This pattern used to provoke a 
+# complaint that it was too complicated.
+
+/(?:\[A|B|C|D|E|F|G|H|I|J|]{200}Z)/expand
+
 # End of testinput2 
 Error -63: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data