[Bug libstdc++/105810] __glibcxx_assert can be improved greatly.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105810

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #2)
> Specifically, the suggested implementation is:
> 
> template<typename __glibcxxassertiontype>
> [[noreturn,__gnu__::__cold__,__gnu__::__noinline__]]
> inline  void __my_glibcxx_constexpr_assert() noexcept
> {
>     constexpr __glibcxxassertiontype __assertinfo;
>    
> __glibcxx_assert_fail(__assertinfo.__glibcxx_assertion_file,__assertinfo.
> __glibcxx_assertion_line,
>        
> __assertinfo.__glibcxx_pretty_function,__assertinfo.
> __glibcxx_assertion_condition);
> }
> 
> #define my_glibcxx_assert(_Condition) \
>   { \
>   if (!bool(_Condition))[[unlikely]]	\

N.B. we can't use [[unlikely]] in C++98 mode, it needs to be __builtin_expect.
We can't even use [[unlikely]] in C++11, it would need to be [[__unlikely__]].

>   {							\
>     \
>     constexpr char const* __glibcxx_pretty_function_impl =
> __PRETTY_FUNCTION__;\
>     struct __glibcxxassertion{\
>         char const* __glibcxx_assertion_file=__FILE__;\
>         int __glibcxx_assertion_line=__LINE__;\
>         char const* __glibcxx_pretty_function="";\
>         char const* __glibcxx_assertion_condition=#_Condition;\
>     };\
>     __my_glibcxx_constexpr_assert<__glibcxxassertion>();				\

We can't use a local class as a template argument in C++98, because the type
has no linkage.