In rts/Printer.c, print exact UPDATE_FRAME type

When printing an update frame in printClosure(), it will not print
the unspecific UPDATE_FRAME, instead it prints BH_UPDATE_FRAME,
NORMAL_UPDATE_FRAME or MARKED_UPDATE_FRAME.

Signed-off-by: Austin Seipp <austin@well-typed.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/rts/Printer.c b/rts/Printer.c
index db2e7be8c8..ca9ca496b5 100644
--- a/rts/Printer.c
+++ b/rts/Printer.c
@@ -263,7 +263,7 @@ printClosure( StgClosure *obj )
     case UPDATE_FRAME:
         {
             StgUpdateFrame* u = (StgUpdateFrame*)obj;
-            debugBelch("UPDATE_FRAME(");
+            debugBelch("%s(", info_update_frame(obj));
             printPtr((StgPtr)GET_INFO((StgClosure *)u));
             debugBelch(",");
             printPtr((StgPtr)u->updatee);
@@ -389,6 +389,24 @@ printClosure( StgClosure *obj )
     }
 }
 
+// If you know you have an UPDATE_FRAME, but want to know exactly which.
+char *info_update_frame(StgClosure *closure) {
+    // Note: We intentionally don't take the info table pointer as
+    // an argument. As it will be confusing whether one should pass
+    // it pointing to the code or struct members when compiling with
+    // TABLES_NEXT_TO_CODE.
+    const StgInfoTable *info = closure->header.info;
+    if (info == &stg_upd_frame_info) {
+        return "NORMAL_UPDATE_FRAME";
+    } else if (info == &stg_bh_upd_frame_info) {
+        return "BH_UPDATE_FRAME";
+    } else if (info == &stg_marked_upd_frame_info) {
+        return "MARKED_UPDATE_FRAME";
+    } else {
+        return "ERROR: Not an update frame!!!";
+    }
+}
+
 /*
 void printGraph( StgClosure *obj )
 {