[Qemu-devel] Re: [PATCH 1/4] Add a scatter-gather list type and accessors

[Avi Kivity <avi@redhat.com>]

Anthony Liguori wrote:
>>
>> Is it possible to have a blanket license for files which don't have 
>> explicit terms?  I don't much like boilerplate.
>
> I'd greatly prefer not to.  You can refer to a COPYING and we can have 
> a default COPYING file but a copyright is really needed as far as I 
> understand it.
>

Okay.  I'll add an explicit license and leave the generic license to our 
esteemed maintainers.

>>> Would be nice to check for malloc failures and fail gracefully at 
>>> least.
>>
>> Do you mean an exit(1)?  If so we could just put it in qemu_malloc().
>
> In theory, some users may be able to cope with malloc failure.  In 
> practice, I don't think anyone can.  I'm open to suggestion.

malloc() will never fail on Linux with overcommit enabled; since Linux 
is fairly useless without overcommit, it means you'll never see a failure.

Other ways of allocating memory (stack growth, first access to anonymous 
memory) are not covered.  They can fail (most ungracefully) without 
strict overcommit control.

So I suggest to have qemu_malloc() and its friends abort on failure.

>> I expect this to trigger rarely since the allocation hint should 
>> suffice nearly 100% of the time.  But in case we miss, it's better to 
>> reallocate as little as possible.
>>
>> (what I really want is std::vector<>)
>
> Which I'm pretty sure has a linear growth strategy :-)

Not in any of the implementations I'm familiar with.  I believe 
std::vector<> is required to have amortized O(1) append operations.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.