Below is approach to the "problem" from a bit different angle - using alias-permitting type definitions consistently where necessary - so assuring compiler won't (shouldn't ?) pursue any funny ideas no matter what. I'd guess it's the "right" thing to do - aside from going kernel way and using -fno-strict-aliasing everywhere (or #pragmas). The compilation goes cleanly at Wstrict-aliasing=1 - so most aggresive yet most dumb at the same time (note, not checked on 4.7, but obviously I included necessary equivalent changes to the Jes's patch). Anyway - side effects of Wstrict-aliasing=1 are false positives - quite a few of them actually (funcion argument casts where only pointers are involved, some pointers which are not dereferenced "nearby" and/or in the same block) - but false negatives should be (almost ?) nonexistent. As mdadm is rather critical, and itself compiled with Wall, Wextra and Werror - I assume to be extra careful - this should complement those settings well. On a bad side of this approach - it doesn't necessary make the code prettier, and might make people ask "the hell is this ...". About the necessary smokescreens: - mentioned function calls (mostly posix_memalign()) are out of our control (like any other external library provided thing), still gcc will complain about argument casts - respecting =1 warning settings. Quieting is simple - either single (void *) or (void_pa *). As we actually use the latter typedef on a few occasions, so it got used here. - when may_alias struct is defined, any references to itself inside the definition (next/prev pointers, etc.) will "lose" may_alias on the struct. Similary, if struct is mentioned before its complete definition - the same thing will occur. The latter is the reason why #include "msg.h" was moved after mdinfo's related definitions. Also see below: - some of the uses changes are also needed to avoid "incompatible pointer cast" warnings - which show up after adding may_alias types (e.g., gcc will consider (__u64 *) and (__u64_a *) as incompatible). Either way, for your consideration. Michal Soltys (1): compile cleanly with -Wstrict-aliasing=1 Grow.c | 14 ++++++------ Makefile | 2 +- bitmap.h | 2 +- managemon.c | 13 ++++++----- md5.h | 1 + mdadm.h | 13 +++++++++- part.h | 4 +- restripe.c | 11 ++++++--- sha1.c | 8 ++---- super-ddf.c | 64 +++++++++++++++++++++++++------------------------------- super-gpt.c | 2 +- super-intel.c | 37 +++++++++++++++++---------------- super-mbr.c | 4 +- super0.c | 14 +++++++----- super1.c | 17 +++++++++------ util.c | 7 +++-- 16 files changed, 113 insertions(+), 100 deletions(-) -- 1.7.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
