--- On Sat, 11/6/10, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > Unfortunately I don't have a copy of the C standard here to > consult. > However... Although I'm perfectly willing to believe > that the standard > requires fields in a structure to be initialized to 0 if > they > aren't mentioned explicitly in the initializer, I'm > considerably more > doubtful that it also requires padding to be initialized! ISTR initialization-to-zero is the standard behavior defined for all _memory_ that gets initialized ... not just named fields ... whether the init is "static", "bss", or not. > > And I certainly wouldn't want to depend on compilers > _always_ using > memset to do this initialization. Of course not; just rely on init-to-zero, and let the compiler worry about efficiency. In some cases memset(); in others, the result might be as if memset were inlined, so only a few "write a zero at this address" type instructions would be needed. > > > There's certainly a fair amount of code I've seen > > that uses runtime initializers like that, to zero > > memory. I can't believe i's _all_ broken! > ;) > > Zeroing memory that belongs to a declared field is > different from > zeroing padding bytes. Maybe what you remember seeing > is the first and > not the second. I remember seeing both, and at one point looking at the issue to verify that padding was treated uniformly (like other memory). Also, writing code that relied on zero-initted padding. - Dave -- 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
