On Wed, Nov 24, 2010 at 11:46:33AM +0000, PÃdraig Brady wrote: >On 24/11/10 11:05, AmÃrico Wang wrote: >> On Wed, Nov 24, 2010 at 10:44:50AM +0000, PÃdraig Brady wrote: >>> On 23/11/10 18:02, Andreas Dilger wrote: >>>> On 2010-11-23, at 07:45, walter harms wrote: >>>>> Maybe we can convince the gcc people to make 0 padding default. That will not solve the problems for other compilers but when they claim "works like gcc" we can press then to support this also. I can imagine that this will close some other subtle leaks also. >>>> >>>> It makes the most sense to tackle this at the GCC level, since the added overhead of doing memset(0) on the whole struct may be non-trivial for commonly-used and/or large structures. Since GCC is already explicitly zeroing the _used_ fields in the struct, it can much more easily determine whether there is padding in the structure, and zero those few bytes as needed. >>> >>> Zero padding structs is part of C90. Details here: >>> http://www.pixelbeat.org/programming/gcc/auto_init.html >> >> Nope. >> >>> >>> gcc doesn't zero pad when _all_ elements are specified. >>> >> >> That is what gcc does, not what C standard specifies. > >Looks like gcc is following the standard exactly. > >C90 - 6.5.7 >C99 - 6.7.8 > > If there are fewer initializers in a brace-enclosed list than > there are elements or members of an aggregate ... the remainder > of the aggregate shall be initialized implicitly the same as > objects that have static storage duration. > Depends on if "the remainder of the aggregate" includes padding bytes or not. -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
