Messages in this thread | | | Date | Mon, 20 Jan 2020 09:18:58 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve |
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On Fri, Jan 17, 2020 at 10:48:19AM -0800, Eric Dumazet wrote: > > > On 1/17/20 10:38 AM, Arvind Sankar wrote: > > On Fri, Jan 17, 2020 at 10:16:45AM -0800, Eric Dumazet wrote: > >> Wasńt it the case back in 2016 already for linux-4.8 ? > >> > >> What will prevent someone to send another report to netdev/lkml ? > >> > >> -fno-strict-overflow support is not a prereq for CONFIG_UBSAN. > >> > >> Fact that we kept in lib/ubsan.c and lib/test_ubsan.c code for > >> test_ubsan_add_overflow() and test_ubsan_sub_overflow() is disturbing. > >> > > > > No, it was bumped in 2018 in commit cafa0010cd51 ("Raise the minimum > > required gcc version to 4.6"). That raised it from 3.2 -> 4.6. > > > > This seems good to me, for gcc at least. > > Maybe it is time to enfore -fno-strict-overflow in KBUILD_CFLAGS > instead of making it conditional.
IIRC there was a bug in UBSAN vs -fwrapv/-fno-strict-overflow that was only fixed in gcc-8 or 9 or so.
So while the -fwrapv/-fno-strict-overflow flag has been correctly supported since like forever, UBSAN was buggy until quite recent when used in conjustion with that flag.
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