On Thu, 5 Jul 2012 00:14:14 +0300 Konstantin Belousov <kostikbel_at_gmail.com> wrote: > On Thu, Jul 05, 2012 at 12:32:01AM +0900, Taku YAMAMOTO wrote: > > On Wed, 04 Jul 2012 17:08:30 +0200 > > Dimitry Andric <dim_at_FreeBSD.org> wrote: > > > > > On 2012-07-04 16:33, Taku YAMAMOTO wrote: > > > > For people having SIGBUS with clang-build world + gcc-build binaries, > > > > > > > > > > > > In short words, for any libraries (and never forget about rtld-elf!) > > > > which are potentially called from arbitrary binaries, > > > > compile them with either -mstackrealign or -mstack-alignment=8! > > > > > > > > The detail is as follows. > > > > > > > > I've observed that clang carelessly expects the stack being aligned at > > > > 16 byte boundary. > > > > > > Eh, this is a requirement of the amd64 ABI. Any compiler that *doesn't* > > > align the stack on 16-byte boundaries is basically broken. Or are you > > > experiencing this on i386? Even there, 16-byte alignment would be much > > > better in combination with SSE instructions (which arent' enabled by > > > default, btw). > > > > Oops, I had to be clear about that! > > Yes, the experiment was took on i386 (actually -march=pentium4). > > > > > Note that you would get the same issue with newer versions of gcc, which > > > will also assume this alignment. > > > > Interesting, but the base gcc we currently have won't on i386, I think. > > (I occationally get bitten by similar problem when using -ftree-vectorize) > As far as I understand the rules, $esp % 16 must be zero before call > instruction is executed. I googled and found that it is enforced by MacOS X ABI for IA32 but i386 SysV ABI defines otherwise (8 bytes instead of 16 bytes). > i386 csu explicitely aligns the stack before calling into C land, everything > else should be the C compiler own offence :). Unfortunately it is difficult when we have to deal with binaries produced by random compilers, such as Win32 app via wine, mplayer with win32-codecs, etc. ;) JITs, like Java and mono, also have possibility to become victims if they emit native codes without paying attention to the stack alignment, though I'm not sure. Just my random thoughts, -- -|-__ YAMAMOTO, Taku | __ < <taku_at_tackymt.homeip.net> - A chicken is an egg's way of producing more eggs. -Received on Thu Jul 05 2012 - 17:15:25 UTC
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