Fix stackoverflow in Re_str.split

Make sure that searching in a string always does progress. Also add
general + regression split tests.

Fix #90

lib/re_str.ml

@@ -235,14 +235,20 @@ let global_replace expr repl text =
 and replace_first expr repl text =
   substitute_first expr (replacement_text repl) text
 
+let search_forward_progress re s p =
+  let pos = search_forward re s p in
+  if match_end () > p then pos
+  else if p < String.length s then search_forward re s (p + 1)
+  else raise Not_found
+
 let bounded_split expr text num =
   let start =
     if string_match expr text 0 then match_end() else 0 in
   let rec split start n =
     if start >= String.length text then [] else
     if n = 1 then [string_after text start] else
       try
-        let pos = search_forward expr text start in
+        let pos = search_forward_progress expr text start in
         String.sub text start (pos-start) :: split (match_end()) (n-1)
       with Not_found ->
         [string_after text start] in
@@ -255,7 +261,7 @@ let bounded_split_delim expr text num =
     if start > String.length text then [] else
     if n = 1 then [string_after text start] else
       try
-        let pos = search_forward expr text start in
+        let pos = search_forward_progress expr text start in
         String.sub text start (pos-start) :: split (match_end()) (n-1)
       with Not_found ->
         [string_after text start] in
@@ -270,7 +276,7 @@ let bounded_full_split expr text num =
     if start >= String.length text then [] else
     if n = 1 then [Text(string_after text start)] else
       try
-        let pos = search_forward expr text start in
+        let pos = search_forward_progress expr text start in
         let s = matched_string text in
         if pos > start then
           Text(String.sub text start (pos-start)) ::

lib_test/test_str.ml

@@ -1,4 +1,5 @@
 open Fort_unit
+open OUnit2
 
 module type Str_intf = module type of Str
 
@@ -27,6 +28,10 @@ end
 module T_str = Test_matches(Str)
 module T_re = Test_matches(Re_str)
 
+let split_convert = List.map (function
+    | Str.Text s -> Re_str.Text s
+    | Str.Delim s -> Re_str.Delim s)
+
 let eq_match ?pos ?case r s =
   expect_equal_app
     ~msg:(str_printer s)
@@ -135,4 +140,29 @@ let _ =
     eq_match ~case:false "abc"    "ABC";
   );
 
+  expect_pass "split tests" (fun () ->
+      let printer = list_printer (fun x -> x) in
+      let split_printer =
+        list_printer (function
+            | Re_str.Delim s -> "Delim " ^ s
+            | Re_str.Text s -> "Text " ^ s) in
+      List.iter (fun (re, s) ->
+          let re1 = Str.regexp re in
+          let re2 = Re_str.regexp re in
+          assert_equal ~printer:split_printer
+            (split_convert (Str.full_split re1 s))
+            (Re_str.full_split re2 s);
+          assert_equal ~printer
+            (Str.split_delim re1 s)
+            (Re_str.split_delim re2 s);
+          assert_equal ~printer
+            (Str.split re1 s)
+            (Re_str.split re2 s)
+        )
+        [ "re", ""
+        ; " ", "foo bar"
+        ; "\b", "one-two three"
+        ; "[0-9]", "One3TwoFive"]
+    );
+
   run_test_suite "test_str"