Re: [Qemu-devel] [PULL v3 00/53] Misc changes for 2017-01-12

[Paolo Bonzini <pbonzini@redhat.com>]

On 16/01/2018 14:47, Peter Maydell wrote:
> On 16 January 2018 at 13:41, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On 16/01/2018 13:06, Peter Maydell wrote:
>>>> ASAN is enabled by default if available when --enable-debug. We could
>>>> add more flags if that helps.
>>> Configure switches should work like this:
>>>  * default: use feature if present, but don't complain if not present
>>>    or not usable
>>>  * --enable-foo: use feature. if feature not present, complain and
>>>    fail configure
>>>  * --disable-foo: don't test for or use feature
>>>
>>
>> However, --enable-debug has never worked like this (the "default" part)...
> 
> True, but -g, no optimization isn't really something we want to
> default to :-)

Same for ASAN. :-)

> I think the general principle that unless the user
> specifically said they cared about the address sanitizer we shouldn't
> complain if it happens not to work on this host is still a good one.

Yes, I agree.

So we need two options:

* --enable-asan defaults to not used, but also fails configure if ASAN
is not available/usable.

* if we want to have --enable-debug enable ASAN, it should however _not_
fail configure if ASAN is not available/usable.  (I am not sure anymore
it's a good idea).

The questions are:

* should fiber support be required for --enable-asan?  What is the
difference in the quality of the reports?

* if not, and assuming --enable-debug tries to enable ASAN, should
--enable-debug complain if fiber support is not required?  Should
--enable-debug enable ASAN if fiber support is not available?

* if --enable-debug does *not* try to enable ASAN, should test-debug add
--enable-asn?  (I think so).

Paolo