jlaitine commented on code in PR #8176:
URL: https://github.com/apache/nuttx/pull/8176#discussion_r1080851962
##########
mm/mempool/mempool_multiple.c:
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@@ -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:
sure it would! Cleanest solution is always first cast the void * to the real
target type ptr and then do arithmetic. This also gives the compiler the
opportunity to know the maximum result size. intptr_t usage is IMHO useless
almost always, and just think about it's bit size (it is minimum the same size
of pointer + 1 bit). It also doesn't exist on all platforms (not sure if posix
enfoces the existence though, not going to check it up now...).
With pointers it is always safe and portable to do pointer arithmetic, but
not on void * since by the standard you can't (obviously because of size of
void). But if you don't know the target type, you always get the same result as
gcc extension by casting to char *. So changing void * arithmetic by casting
the pointers to char * doesn't change the existing functionality.
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