Fix bogus use of "long" in AllocSetCheck()

Because long is 32-bit on 64-bit Windows, it isn't a good datatype to
store the difference between 2 pointers.  The under-sized type could
overflow and lead to scary warnings in MEMORY_CONTEXT_CHECKING builds,
such as:

WARNING:  problem in alloc set ExecutorState: bad single-chunk %p in block %p

However, the problem lies only in the code running the check, not from
an actual memory accounting bug.

Fix by using "Size" instead of "long".  This means using an unsigned
type rather than the previous signed type.  If the block's freeptr was
corrupted, we'd still catch that if the unsigned type wrapped.  Unsigned
allows us to avoid further needless complexities around comparing signed
and unsigned types.

Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Backpatch-through: 13
Discussion: https://postgr.es/m/CAApHDvo-RmiT4s33J=aC9C_-wPZjOXQ232V-EZFgKftSsNRi4w@mail.gmail.com

diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 5beebc1c129e0a90a15c66ed83961e8c478ad6cf..49e15d40802267824dcdbbe26c35061690227e7b 100644 (file)
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -1431,9 +1431,9 @@ AllocSetCheck(MemoryContext context)
         prevblock = block, block = block->next)
    {
        char       *bpoz = ((char *) block) + ALLOC_BLOCKHDRSZ;
-       long        blk_used = block->freeptr - bpoz;
-       long        blk_data = 0;
-       long        nchunks = 0;
+       Size        blk_used = block->freeptr - bpoz;
+       Size        blk_data = 0;
+       Size        nchunks = 0;
 
        if (set->keeper == block)
            total_allocated += block->endptr - ((char *) set);