On Sun, Aug 20, 2017 at 3:19 PM, Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > 2017-07-20 16:24 GMT+09:00 Arnd Bergmann <arnd@xxxxxxxx>: >> - enable all three warnings with "make W=1" in 4.13, but leave them >> disabled by default. >> - backport Linus' patch, plus the follow-up for W=1 to stable kernels, >> to allow stable kernels to build cleanly >> - backport the patches that address any other gcc-7 warnings, as >> well as those that are not obvious false-positives to stable kernels >> - In 4.14+, use my version above and address all int-in-bool-context >> and format-overflow warnings, but only use -Wformat-truncation >> with make W=1. >> > > Talking about 4.14+, shall we move -Wformat-truncation > from the top Makefile (always disable) to > Makefile.extrawarn (enable with W=1) ? I dropped the ball on this one, sorry. I think we should do this for all three warnings (format-overflow, format-truncation and int-in-bool-context) for the time being. In case of format-truncation, there are countless warnings, most of them false-postives, so we simply can't enable them by default. For -Wformat-overflow, there is one patch that I need to rewrite, all my other patches are pending for 4.14, see https://patchwork.kernel.org/patch/9840801/ for the missing one. This should be trivial to fix. However, enabling CONFIG_UBSAN_SANITIZE_ALL results in seven additional false positives. I created an patch for this in https://pastebin.com/CD7nhRNp but can't submit that as it's obviously bogus. I reported the gcc bug as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81592 What we could do there is to disable the warning if CONFIG_UBSAN_SANITIZE_ALL is turned on (like we do for -Wmaybe-uninitialized in CONFIG_UBSAN_SANITIZE_ALL) but leave it on otherwise. I submitted patches for all -Wint-in-bool-context in arm/arm64/x86 randconfig builds, but there are still six known warnings for which my patches did not get queued for 4.14. I have to revisit those all to decide whether we can find an acceptable workaround in the kernel and enable the warning again by default, or leave it in W=1 until gcc improves enough. Arnd