P.S. I think gcc might have been reason why I misremembered how assert does or does not work in constexpr, so maybe that is the reason why it is commented out in clamp? It was fixed few years ago(GCC 9). https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86678 On Sat, Aug 21, 2021 at 9:05 PM Ivan Matek wrote:

On Sat, Aug 21, 2021 at 5:56 PM Peter Dimov via Boost < boost@lists.boost.org> wrote:

...

It does. https://www.godbolt.org/z/KhPja6cEs

Ah my mistake. :( Do you then maybe know why boost clamp has commented out the assert in implementation?

https://github.com/boostorg/algorithm/blob/c9077bd49580bddfaa8a5c71abc4022a2... I presumed it is to avoid problems with assert and constexpr, but as you now I learned assert works fine since C++14.

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

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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

Thanks

On 8/25/21 2:43 PM, Peter Dimov wrote:

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

Doh (smacks head)

Thank you !  😁