Messages in this thread | | | Date | Tue, 5 Mar 2019 19:58:54 +1100 (AEDT) | From | Finn Thain <> | Subject | Re: [m68k:master 1174/1174] arch/m68k/include/asm/string.h:72:25: warning: '__builtin_memcpy' forming offset 8 is out of the bounds [0, 7] |
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On Tue, 5 Mar 2019, Geert Uytterhoeven wrote:
> On Tue, Mar 5, 2019 at 3:58 AM Finn Thain <fthain@telegraphics.com.au> wrote: > > On Tue, 5 Mar 2019, Finn Thain wrote: > > > Looks bogus to me. > > > > > > If you change memcpy to __builtin_memcpy, then we avoid the macro and the > > > warning changes to, > > > > > > ./include/linux/string.h:456:3: warning: '__builtin_memcpy' forming offset [7, 8] is out of the bounds [0, 6] [-Warray-bounds] > > > __builtin_memcpy(dest, src, dest_len); > > > > > > The compiler has nothing to complain about here. dest is known to be > > > id->fr and dest_len is known to be sizeof(id->fr). > > > > > > The error message indicates that gcc has applied the bounds [0, 6] to dest > > > when in fact those are the bounds for src. > > > > > > > My mistake. GCC is right, it seems memcpy will read past the end of > > "5.0.0+". > > But only if the else branch is taken, which is not the case. >
You and I know that, because we can see what values get passed to memcpy_and_pad(). But how is gcc to know that?
If we replace strlen with __builtin_strlen, this problem goes away. It's interesting that the kernel's strlen implementation in include/linux/string.h can't achieve this.
--
> Gr{oetje,eeting}s, > > Geert > >
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