Commit 7dc0cd52 authored by Simon Marlow's avatar Simon Marlow
Browse files

Cast some more nats to StgWord to be on the safe side

And add a comment about the dangers of int overflow
parent 897231aa
......@@ -118,6 +118,16 @@ static void initMBlock(void *mblock);
--------------------------------------------------------------------------- */
/* ---------------------------------------------------------------------------
WATCH OUT FOR OVERFLOW
Be very careful with integer overflow here. If you have an
expression like (n_blocks * BLOCK_SIZE), and n_blocks is an int or
a nat, then it will very likely overflow on a 64-bit platform.
Always cast to StgWord (or W_ for short) first: ((W_)n_blocks * BLOCK_SIZE).
--------------------------------------------------------------------------- */
#define MAX_FREE_LIST 9
// In THREADED_RTS mode, the free list is protected by sm_mutex.
......@@ -337,7 +347,7 @@ allocGroup (nat n)
if (ln == MAX_FREE_LIST) {
#if 0
if ((mblocks_allocated * MBLOCK_SIZE_W - n_alloc_blocks * BLOCK_SIZE_W) > (1024*1024)/sizeof(W_)) {
if (((W_)mblocks_allocated * MBLOCK_SIZE_W - (W_)n_alloc_blocks * BLOCK_SIZE_W) > (1024*1024)/sizeof(W_)) {
debugBelch("Fragmentation, wanted %d blocks:", n);
RtsFlags.DebugFlags.block_alloc = 1;
checkFreeListSanity();
......@@ -472,7 +482,7 @@ freeGroup(bdescr *p)
p->gen = NULL;
p->gen_no = 0;
/* fill the block group with garbage if sanity checking is on */
IF_DEBUG(sanity,memset(p->start, 0xaa, p->blocks * BLOCK_SIZE));
IF_DEBUG(sanity,memset(p->start, 0xaa, (W_)p->blocks * BLOCK_SIZE));
if (p->blocks == 0) barf("freeGroup: block size is zero");
......@@ -586,7 +596,7 @@ splitBlockGroup (bdescr *bd, nat blocks)
low_mblocks = 1 + (blocks - BLOCKS_PER_MBLOCK) / (MBLOCK_SIZE / BLOCK_SIZE);
high_mblocks = (bd->blocks - blocks) / (MBLOCK_SIZE / BLOCK_SIZE);
new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + low_mblocks * MBLOCK_SIZE_W);
new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + (W_)low_mblocks * MBLOCK_SIZE_W);
initMBlock(new_mblock);
new_bd = FIRST_BDESCR(new_mblock);
new_bd->blocks = MBLOCK_GROUP_BLOCKS(high_mblocks);
......
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