[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 #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
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]]    \
  {                                                     \
    \
    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>();                       
        \
  }\
  }


This instantiates a new instance of __my_glibcxx_constexpr_assert<T> with a new
T for every assertion, but the actual call to __glibcxx_assert_fail is in a
cold function instead of inlined into the assertion.