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authorJohn Högberg <[email protected]>2018-10-23 09:37:16 +0200
committerJohn Högberg <[email protected]>2018-10-25 07:47:23 +0200
commit19972f42719c6e9357e33e123d00b681213022dc (patch)
tree433d99867131facc091597c7c563ab9287943de1
parent639bb57cf7d6550a48608dc827a6fd3aed1af005 (diff)
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Fix trapping in lists:reverse/2
The first stage wasn't bounded by reductions, and it bumped far more reductions than it should have due to a logic bug.
-rw-r--r--erts/emulator/beam/erl_bif_lists.c34
1 files changed, 20 insertions, 14 deletions
diff --git a/erts/emulator/beam/erl_bif_lists.c b/erts/emulator/beam/erl_bif_lists.c
index 395be67a90..9b2b8aaab6 100644
--- a/erts/emulator/beam/erl_bif_lists.c
+++ b/erts/emulator/beam/erl_bif_lists.c
@@ -283,7 +283,7 @@ static BIF_RETTYPE lists_reverse_alloc(Process *c_p,
{
static const Uint CELLS_PER_RED = 40;
- Eterm *heap_top, *heap_end;
+ Eterm *alloc_top, *alloc_end;
Uint cells_left, max_cells;
Eterm list, tail;
Eterm lookahead;
@@ -305,18 +305,18 @@ static BIF_RETTYPE lists_reverse_alloc(Process *c_p,
BIF_ERROR(c_p, BADARG);
}
- heap_top = HAlloc(c_p, 2 * (max_cells - cells_left));
- heap_end = heap_top + 2 * (max_cells - cells_left);
+ alloc_top = HAlloc(c_p, 2 * (max_cells - cells_left));
+ alloc_end = alloc_top + 2 * (max_cells - cells_left);
- while (heap_top < heap_end) {
+ while (alloc_top < alloc_end) {
Eterm *pair = list_val(list);
- tail = CONS(heap_top, CAR(pair), tail);
+ tail = CONS(alloc_top, CAR(pair), tail);
list = CDR(pair);
ASSERT(is_list(list) || is_nil(list));
- heap_top += 2;
+ alloc_top += 2;
}
if (is_nil(list)) {
@@ -333,7 +333,7 @@ static BIF_RETTYPE lists_reverse_onheap(Process *c_p,
{
static const Uint CELLS_PER_RED = 60;
- Eterm *heap_top, *heap_end;
+ Eterm *alloc_start, *alloc_top, *alloc_end;
Uint cells_left, max_cells;
Eterm list, tail;
@@ -343,21 +343,27 @@ static BIF_RETTYPE lists_reverse_onheap(Process *c_p,
cells_left = max_cells = CELLS_PER_RED * (1 + ERTS_BIF_REDS_LEFT(c_p));
ASSERT(HEAP_LIMIT(c_p) >= HEAP_TOP(c_p) + 2);
- heap_end = HEAP_LIMIT(c_p) - 2;
- heap_top = HEAP_TOP(c_p);
+ alloc_start = HEAP_TOP(c_p);
+ alloc_end = HEAP_LIMIT(c_p) - 2;
+ alloc_top = alloc_start;
- while (heap_top < heap_end && is_list(list)) {
+ /* Don't process more cells than we have reductions for. */
+ alloc_end = MIN(alloc_top + (cells_left * 2), alloc_end);
+
+ while (alloc_top < alloc_end && is_list(list)) {
Eterm *pair = list_val(list);
- tail = CONS(heap_top, CAR(pair), tail);
+ tail = CONS(alloc_top, CAR(pair), tail);
list = CDR(pair);
- heap_top += 2;
+ alloc_top += 2;
}
- cells_left -= (heap_top - heap_end) / 2;
+ cells_left -= (alloc_top - alloc_start) / 2;
+ HEAP_TOP(c_p) = alloc_top;
+
+ ASSERT(cells_left >= 0 && cells_left <= max_cells);
BUMP_REDS(c_p, (max_cells - cells_left) / CELLS_PER_RED);
- HEAP_TOP(c_p) = heap_top;
if (is_nil(list)) {
BIF_RET(tail);