[LLVMdev] Ideas for making llvm-config --cxxflags more useful

[Justin Bogner]

Mehdi Amini <mehdi.amini at apple.com> writes:
>> On Aug 3, 2015, at 10:24 AM, Chris Bieneman <beanz at apple.com> wrote:
>> 
>> Hey Tom,
>> 
>> I’m not a regular user of llvm-config, but this sounds completely
>> right to me, and it would be a significant improvement over what we
>> have now.
>> 
>> The only question I want to raise is, what about NDEBUG? There are
>> headers that conditionalize on NDEBUG, which could lead to ABI
>> incompatibility in the C++ API.
>
> Is it something that can be fixed or would it be too complicated to handle? 
> It would be nice in general to be able to link a “Non assert” build of
> Clang with an “Assert" version of LLVM (and vice-versa).
>
> And on the original topic: +1 for Tom proposal/goal, it makes sense to me.

It's probably possible, but I think it's quite a bit of work from where
we are now. A lot of our headers are not ABI compatible between NDEBUG
and !NDEBUG.

llvm-config does already provide --assertion-mode to check NDEBUG in
particular. I'm not sure if that's sufficient though, since it's easy to
do the wrong thing when you need to use two different calls to get the
right set of flags to be able to grok llvm headers.