Fixing bug #4105: poor escaping in the protocol between CoqIDE and coqtop.

Printing invalid UTF-8 string startled GTK too much, leading to CoqIDE dying
improperly. We now check that all strings outputed by Coq are proper UTF-8.
This is not perfect, as CoqIDE will sometimes truncate strings which contains
the null character, but at least it should not crash.

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/unicode.ml b/lib/unicode.ml
index 1765e93dcd..cfaa73cc11 100644
--- a/lib/unicode.ml
+++ b/lib/unicode.ml
@@ -168,6 +168,13 @@ let next_utf8 s i =
        (c land 0x3F) lsl 6 + (d land 0x3F)
   else err ()
 
+let is_utf8 s =
+  let rec check i =
+    let (off, _) = next_utf8 s i in
+    check (i + off)
+  in
+  try check 0 with End_of_input -> true | Invalid_argument _ -> false
+
 (* Check the well-formedness of an identifier *)
 
 let initial_refutation j n s =