rts: Fix Arena blocks accounting for MBlock sized allocations

When requesting more than BLOCKS_PER_MBLOCK blocks allocGroup can return a
different number of blocks than requested. Here we use the number of
requested blocks, however arenaFree will subtract the actual number of
blocks we got from arena_blocks (possibly) resulting in a negative value
and triggering ASSERT(arena_blocks >= 0).

1 files changed, 1 insertions, 1 deletions

diff --git a/rts/Arena.c b/rts/Arena.c
index a4ff11be7d..1d6dac623c 100644
--- a/rts/Arena.c
+++ b/rts/Arena.c
@@ -82,7 +82,7 @@ arenaAlloc( Arena *arena, size_t size )
         // allocate a fresh block...
         req_blocks =  (W_)BLOCK_ROUND_UP(size) / BLOCK_SIZE;
         bd = allocGroup_lock(req_blocks);
-        arena_blocks += req_blocks;
+        arena_blocks += bd->blocks;
 
         bd->gen_no  = 0;
         bd->gen     = NULL;