From fb84058720f8f73006720e4ab489f300dc767a3d Mon Sep 17 00:00:00 2001
From: Mark Shinwell <mshinwell@janestreet.com>
Date: Mon, 29 Feb 2016 12:17:45 +0000
Subject: [PATCH] Fix PR7157 (too many minor collections)

---
 byterun/caml/minor_gc.h |  1 +
 byterun/caml/weak.h     |  1 +
 byterun/minor_gc.c      | 31 +++++++++++++++++--------------
 stdlib/weak.ml          |  7 +++++--
 4 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/byterun/caml/minor_gc.h b/byterun/caml/minor_gc.h
index e4c57958f..e6f6d97b4 100644
--- a/byterun/caml/minor_gc.h
+++ b/byterun/caml/minor_gc.h
@@ -87,6 +87,7 @@ static inline void add_to_ephe_ref_table (struct caml_ephe_ref_table *tbl,
   ephe_ref = tbl->ptr++;
   ephe_ref->ephe = ar;
   ephe_ref->offset = offset;
+  Assert(ephe_ref->offset < Wosize_val(ephe_ref->ephe));
 }
 
 #endif /* CAML_MINOR_GC_H */
diff --git a/byterun/caml/weak.h b/byterun/caml/weak.h
index 9f7e3781a..5cfc8133b 100644
--- a/byterun/caml/weak.h
+++ b/byterun/caml/weak.h
@@ -29,6 +29,7 @@ extern value caml_ephe_none;
        others       2..:  keys;
 
     A weak pointer is an ephemeron with the data at caml_ephe_none
+    If fields are added, don't forget to update weak.ml [additional_values].
  */
 
 #define CAML_EPHE_LINK_OFFSET 0
diff --git a/byterun/minor_gc.c b/byterun/minor_gc.c
index 548a350e5..ef75bc0f3 100644
--- a/byterun/minor_gc.c
+++ b/byterun/minor_gc.c
@@ -85,9 +85,9 @@ static void alloc_generic_table (struct generic_table *tbl, asize_t sz,
   if (tbl->base != NULL) caml_stat_free (tbl->base);
   tbl->base = new_table;
   tbl->ptr = tbl->base;
-  tbl->threshold = tbl->base + tbl->size;
+  tbl->threshold = tbl->base + tbl->size * element_size;
   tbl->limit = tbl->threshold;
-  tbl->end = tbl->base + tbl->size + tbl->reserve;
+  tbl->end = tbl->base + (tbl->size + tbl->reserve) * element_size;
 }
 
 void caml_alloc_table (struct caml_ref_table *tbl, asize_t sz, asize_t rsv)
@@ -280,7 +280,7 @@ void caml_oldify_one (value v, value *p)
 static inline int ephe_check_alive_data(struct caml_ephe_ref_elt *re){
   mlsize_t i;
   value child;
-  for (i = 2; i < Wosize_val(re->ephe); i++){
+  for (i = CAML_EPHE_FIRST_KEY; i < Wosize_val(re->ephe); i++){
     child = Field (re->ephe, i);
     if(child != caml_ephe_none
        && Is_block (child) && Is_young (child)
@@ -371,18 +371,21 @@ void caml_empty_minor_heap (void)
     /* Update the ephemerons */
     for (re = caml_ephe_ref_table.base;
          re < caml_ephe_ref_table.ptr; re++){
-      value *key = &Field(re->ephe,re->offset);
-      if (*key != caml_ephe_none && Is_block (*key) && Is_young (*key)){
-        if (Hd_val (*key) == 0){ /* Value copied to major heap */
-          *key = Field (*key, 0);
-        }else{ /* Value not copied so it's dead */
-          Assert(!ephe_check_alive_data(re));
-          *key = caml_ephe_none;
-          Field(re->ephe,1) = caml_ephe_none;
+      if(re->offset < Wosize_val(re->ephe)){
+        /* If it is not the case, the ephemeron has been truncated */
+        value *key = &Field(re->ephe,re->offset);
+        if (*key != caml_ephe_none && Is_block (*key) && Is_young (*key)){
+          if (Hd_val (*key) == 0){ /* Value copied to major heap */
+            *key = Field (*key, 0);
+          }else{ /* Value not copied so it's dead */
+            Assert(!ephe_check_alive_data(re));
+            *key = caml_ephe_none;
+            Field(re->ephe,1) = caml_ephe_none;
+          }
         }
       }
     }
-    /* Run custom block finalisation of dead minor value */
+    /* Run custom block finalisation of dead minor values */
     for (r = caml_finalize_table.base; r < caml_finalize_table.ptr; r++){
       int hd = Hd_val ((value)*r);
       if (hd != 0){         /* If not oldified the finalizer must be called */
@@ -520,8 +523,8 @@ static void realloc_generic_table
     if (tbl->base == NULL){
       caml_fatal_error (msg_error);
     }
-    tbl->end = tbl->base + tbl->size + tbl->reserve;
-    tbl->threshold = tbl->base + tbl->size;
+    tbl->end = tbl->base + (tbl->size + tbl->reserve) * element_size;
+    tbl->threshold = tbl->base + tbl->size * element_size;
     tbl->ptr = tbl->base + cur_ptr;
     tbl->limit = tbl->end;
   }
diff --git a/stdlib/weak.ml b/stdlib/weak.ml
index ac1f20718..b1d0d7fbd 100644
--- a/stdlib/weak.ml
+++ b/stdlib/weak.ml
@@ -19,7 +19,10 @@ type 'a t;;
 
 external create : int -> 'a t = "caml_weak_create";;
 
-let length x = Obj.size(Obj.repr x) - 2;;
+(** number of additional values in a weak pointer *)
+let additional_values = 2
+
+let length x = Obj.size(Obj.repr x) - additional_values;;
 
 external set : 'a t -> int -> 'a option -> unit = "caml_weak_set";;
 external get : 'a t -> int -> 'a option = "caml_weak_get";;
@@ -162,7 +165,7 @@ module Make (H : Hashtbl.HashedType) : (S with type data = H.t) = struct
         t.table.(t.rover) <- emptybucket;
         t.hashes.(t.rover) <- [| |];
       end else begin
-        Obj.truncate (Obj.repr bucket) (prev_len + 1);
+        Obj.truncate (Obj.repr bucket) (prev_len + additional_values);
         Obj.truncate (Obj.repr hbucket) prev_len;
       end;
       if len > t.limit && prev_len <= t.limit then t.oversize <- t.oversize - 1;