patch: link ubsan into shared libraries

[Nick Lewycky]

On 12 August 2013 16:36, Richard Smith <richard at metafoo.co.uk> wrote:

> LGTM, thanks!
>

Thanks! I'd like to give the other sanitizer folks a chance to complain, so
I'm going to wait until tomorrow before committing it.

On Mon, Aug 12, 2013 at 4:25 PM, Nick Lewycky <nlewycky at google.com> wrote:
>
>> The attached patch causes ubsan to get linked in when building a .so
>> file. This is different from other sanitizers.
>>
>> The other sanitizers are harder to deploy because they rely on replacing
>> malloc. This means that you have to figure out how to link in a single
>> malloc in the final binary.
>>
>> ubsan doesn't need this. You could link a .so file with ubsan, then link
>> the final binary with no knowledge that ubsan was ever involved, and it
>> will work just fine. (Or rather, it will after this patch.) In particular,
>> I can't currently build a python module with ubsan and then load it into a
>> normal python. The attached patch makes this work.
>>
>> The downside to this patch is that we can end up with multiple copies of
>> the ubsan runtime linked in. In reality this works fine because the ubsan
>> runtime doesn't keep much state (and it'd be difficult to make it do so
>> correctly because it has to support calling through files that are a mix of
>> built and not build with ubsan). We'll end up with multiple copies of
>> ubsan's vptr cache, which in turn will probably improve performance by
>> improving locality.
>>
>> Please review!
>>
>> Nick
>>
>>
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>
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