[bad.typeid]

# 17 Language support library [[support]](./#support)

## 17.7 Type identification [[support.rtti]](support.rtti#bad.typeid)

### 17.7.5 Class bad_typeid [bad.typeid]

[ð](#lib:bad_typeid)

namespace std {class bad_typeid : public exception {public:// see [[exception]](exception "17.9.3 Class exception") for the specification of the special member functionsconstexpr const char* what() const noexcept override; };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L3435)

The classbad_typeid defines the type of objects
thrown as exceptions by the implementation to report a null pointer
in atypeid expression ([[expr.typeid]](expr.typeid "7.6.1.8 Type identification"))[.](#1.sentence-1)

[ð](#lib:what,bad_typeid)

`constexpr const char* what() const noexcept override;
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L3450)

*Returns*: An implementation-defined ntbs[.](#2.sentence-1)
