MPR#7815: major GC crash with first-fit policy (#1896)

A fixed-size cache was overflowing. This is the simple fix.
ocaml · Jul 19, 2018 · 1bea41f · 1bea41f
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diff --git a/Changes b/Changes
@@ -1,6 +1,11 @@
 OCaml 4.07 maintenance branch
 -----------------------------
 
+### Bug fixes:
+
+- MPR#7815, GPR#1896: major GC crash with first-fit policy
+  (Stephen Dolan and Damien Doligez, report by Joris Giovannangeli)
+
 - MPR#7820, GPR#1897: Fix Array.of_seq. This function used to apply a circular
   permutation of one cell to the right on the sequence.
   (Thierry Martinez, review by Nicolás Ojeda Bär)

diff --git a/byterun/freelist.c b/byterun/freelist.c
@@ -338,7 +338,7 @@ header_t *caml_fl_allocate (mlsize_t wo_sz)
         mlsize_t oldsz = sz;
 
         prev = flp[i];
-        while (prev != flp[i+1]){
+        while (prev != flp[i+1] && j < FLP_MAX - i){
           cur = Next (prev);
           sz = Wosize_bp (cur);
           if (sz > prevsz){