[PATCH] tbb-backend effective target should check ability to link TBB

[Jonathan Wakely]

On 21/05/19 22:47 +0200, François Dumont wrote:
>On 5/21/19 3:50 PM, Jonathan Wakely wrote:
>>On 20/05/19 21:41 -0700, Thomas Rodgers wrote:
>>>With the addition of "-ltbb" to the v3_target_compile flags (so as to,
>>>you know, actually try to link tbb).
>>>
>>>Tested x86_64-linux, committed to trunk.
>>
>>This didn't work, I still get a FAIL for every pstl test when
>>tbb.x86_64 and tbb-devel.x86_64 are installed but not tbb.i686.
>>
>>Adding -v to RUNTESTFLAGS shows -ltbb wasn't being added to the
>>command, and because the test program didn't actually refer to any TBB
>>symbols, it still linked successfully.
>>
>But the test program still do not refer any TBB symbol. Why is it 
>better ?

Because -ltbb means the linker will give an error if there is no
suitable libtbb. That's true even if no symbols from it are needed.
Try it.

>It looks like it could be a preprocess test.

It used to be a preprocess test, and it didn't work. How can a
preprocess test tell if -ltbb will work?