[GitHub] [nuttx] jlaitine commented on a diff in pull request #8176: Build warning fixes

[GitBox <gi...@apache.org>]

jlaitine commented on code in PR #8176:
URL: https://github.com/apache/nuttx/pull/8176#discussion_r1073475284


##########
mm/mempool/mempool_multiple.c:
##########
@@ -220,7 +220,7 @@ mempool_multiple_get_dict(FAR struct mempool_multiple_s *mpool,
   col = index - (row << mpool->dict_col_num_log2);
   if (mpool->dict[row] == NULL ||
       mpool->dict[row][col].addr != addr ||
-      blk - addr >= mpool->dict[row][col].size)
+      (FAR char *)blk - (FAR char *)addr >= mpool->dict[row][col].size)

Review Comment:
   yes, but then you'd need to do something like (ssize_t)((uintptr_t)blk - (uintptr_t)addr) . otherwise the sign of the calculation may be wrong (never negative but overflown to large positive) as it is compared against unsigned. and this format just looks even uglier (and relies on the fact(?) that sizeof(ssize_t) == sizeof(uintptr_t). which is maybe so, but not by standard (ssize_t just needs to be large enough to cover the whole address area, there is no requirement for it to be exactly the same size... *if* it would be larger this would fail still....  Just keeping pointers as pointers when doing pointer arithmetic is IMHO  cleanest, and then you can also trust that the result is proper signed integer :)
   
   



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