Re: Does boost have an assert that works nicely with constexpr evaluation, and if not should we add one?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2021-08-25 18:43:23

David P. Riedel wrote:
> On 8/21/21 11:54 AM, Peter Dimov via Boost wrote:
> > Ivan Matek wrote:
> >
> >> As you may know assert does not play nicely with constexpr evaluation.
> >
> > It does. https://www.godbolt.org/z/KhPja6cEs
> >
> What am I missing here?
> 
> I click the above link and see the code
> 
> If I compile with gcc x86-64 trunk, I get the following:
> 
> > source>: In function 'int main()':
> > <source>:12:21: error: non-constant condition for static assertion
> >    12 |     static_assert(5 == func(9,1));
> >       |                   ~~^~~~~~~~~~~~
> > In file included from /opt/compiler-explorer/gcc-trunk-
> 20210825/include/c++/12.0.0/cassert:44,
> >                  from <source>:2:
> > <source>:12:28:   in 'constexpr' expansion of 'func(9, 1)'
> > <source>:6:5: error: call to non-'constexpr' function 'void
> __assert_fail(const char*, const char*, unsigned int, const char*)'
> >     6 |     assert(a<b);
> >       |     ^~~~~~

That's because the assertion fails. a=9, b=1.