3 files changed, 24 insertions, 18 deletions
diff --git a/lib/backtrace.ml b/lib/backtrace.ml
index 4955437b3..d64f42f7f 100644
--- a/lib/backtrace.ml
+++ b/lib/backtrace.ml
@@ -26,7 +26,8 @@ type frame = { frame_location : location option; frame_raised : bool; }
 external get_exception_backtrace: unit -> raw_frame array option
   = "caml_get_exception_backtrace"
 
-type t = frame list
+type t = raw_frame array list
+(** List of partial raw stack frames, in reverse order *)
 
 let empty = []
 
@@ -42,15 +43,21 @@ let of_raw = function
   } in
   { frame_location = Some loc; frame_raised = r; }
 
-let push stack = match get_exception_backtrace () with
-| None -> []
-| Some frames ->
-  let len = Array.length frames in
+let rec repr_aux accu = function
+| [] -> accu
+| fragment :: stack ->
+  let len = Array.length fragment in
   let rec append accu i =
     if i = len then accu
-    else append (of_raw frames.(i) :: accu) (succ i)
+    else append (of_raw fragment.(i) :: accu) (succ i)
   in
-  append stack 0
+  repr_aux (append accu 0) stack
+
+let repr bt = repr_aux [] (List.rev bt)
+
+let push stack = match get_exception_backtrace () with
+| None -> []
+| Some frames -> frames :: stack
 
 (** Utilities *)
 
@@ -80,17 +87,12 @@ let add_backtrace e =
     let current = get_exception_backtrace () in
     begin match current with
     | None -> e
-    | Some frames ->
-      let len = Array.length frames in
-      let rec append accu i =
-        if i = len then accu
-        else append (of_raw frames.(i) :: accu) (succ i)
-      in
-      let old = match get_backtrace e with
+    | Some fragment ->
+      let bt = match get_backtrace e with
       | None -> []
       | Some bt -> bt
       in
-      let bt = append old 0 in
+      let bt = fragment :: bt in
       Exninfo.add e backtrace bt
     end
   else e
diff --git a/lib/backtrace.mli b/lib/backtrace.mli
index d5a96e6f7..b5a956573 100644
--- a/lib/backtrace.mli
+++ b/lib/backtrace.mli
@@ -32,9 +32,8 @@ type frame = { frame_location : location option; frame_raised : bool; }
 (** A frame contains two informations: its optional physical location, and
     whether it raised the exception or let it pass through. *)
 
-type t = frame list
-(** Type of backtraces. They're just stack of frames. [None] indicates that we
-    don't care about recording the backtraces. *)
+type t
+(** Type of backtraces. They're essentially stack of frames. *)
 
 val empty : t
 (** Empty frame stack. *)
@@ -42,6 +41,10 @@ val empty : t
 val push : t -> t
 (** Add the current backtrace information to a given backtrace. *)
 
+val repr : t -> frame list
+(** Represent a backtrace as a list of frames. Leftmost element is the outermost
+    call. *)
+
 (** {5 Utilities} *)
 
 val print_frame : frame -> string
diff --git a/lib/errors.ml b/lib/errors.ml
index 75464f2da..157949fcd 100644
--- a/lib/errors.ml
+++ b/lib/errors.ml
@@ -88,6 +88,7 @@ let print_anomaly askreport e =
   let bt_info = match Backtrace.get_backtrace e with
   | None -> mt ()
   | Some bt ->
+    let bt = Backtrace.repr bt in
     let pr_frame f = str (Backtrace.print_frame f) in
     let bt = prlist_with_sep fnl pr_frame bt in
     fnl () ++ hov 0 bt