Make YAML output buffer sizing exponential

src/util/std/gobYaml.ml

@@ -1,3 +1,14 @@
+let to_string' ?(len=65535 * 4) ?encoding ?scalar_style ?layout_style v =
+  assert (len >= 1);
+  let rec aux len =
+    match Yaml.to_string ~len ?encoding ?scalar_style ?layout_style v with
+    | Ok _ as o -> o
+    | Error (`Msg ("scalar failed" | "doc_end failed")) when len < Sys.max_string_length / 2 ->
+      aux (len * 2)
+    | Error (`Msg _) as e -> e
+  in
+  aux len
+
 include Yaml.Util
 
 include GobResult.Syntax

src/witness/yamlWitness.ml

@@ -143,12 +143,11 @@ struct
   }
 end
 
-let yaml_entries_to_file ?(invariants=0) yaml_entries file =
+let yaml_entries_to_file yaml_entries file =
   let yaml = `A yaml_entries in
   (* Yaml_unix.to_file_exn file yaml *)
   (* to_file/to_string uses a fixed-size buffer... *)
-  (* estimate how big it should be + extra in case empty *)
-  let text = match Yaml.to_string ~len:((List.length yaml_entries + invariants) * 8192 + 2048) yaml with
+  let text = match GobYaml.to_string' yaml with
     | Ok text -> text
     | Error (`Msg m) -> failwith ("Yaml.to_string: " ^ m)
   in
@@ -432,7 +431,7 @@ struct
     in
 
     (* Generate invariant set *)
-    let (entries, invariants) =
+    let entries =
       if entry_type_enabled YamlWitnessType.InvariantSet.entry_type then (
         let invariants = [] in
 
@@ -503,10 +502,10 @@ struct
 
         let invariants = List.rev invariants in
         let entry = Entry.invariant_set ~task ~invariants in
-        (entry :: entries, List.length invariants)
+        entry :: entries
       )
       else
-        (entries, 0)
+        entries
     in
 
     let yaml_entries = List.rev_map YamlWitnessType.Entry.to_yaml entries in (* reverse to make entries in file in the same order as generation messages *)
@@ -515,7 +514,7 @@ struct
       (Pretty.dprintf "total generation entries: %d" (List.length yaml_entries), None);
     ];
 
-    yaml_entries_to_file ~invariants yaml_entries (Fpath.v (GobConfig.get_string "witness.yaml.path"))
+    yaml_entries_to_file yaml_entries (Fpath.v (GobConfig.get_string "witness.yaml.path"))
 
   let write () =
     Timing.wrap "yaml witness" write ()