A const-qualified type makes the referenced value read-only through an expression having that type. Attempting to modify such an object should produce a compiler diagnostic. section 5.6.1
Qualification applies at each level
The declaration `char const*const` combines two guarantees: the characters referred to are not writable through the pointer, and the pointer itself cannot be redirected. An array such as `bird` can therefore refer to string literals without storing those characters inside the array. section 5.6.1
Read-only through one type does not guarantee an unchanging value. Another part of the program may access the same object without the qualification and change it. Thus const-qualified objects differ from C23 `constexpr` objects, whose values are known at compile time and guaranteed not to change. section 5.6.1
Keep these rules distinct:
- Treat string literals as read-only, even though their historical C type was retained for backward compatibility rather than declared as `char const[]`. section 5.6.1
- Handle const-qualification carefully in text-processing interfaces, where pointer types and buffer overflow are related safety concerns. section 14.7
extern double const factor; constexpr double π = 3.141'592'653'589'793'238'46;
Compare a declaration-only const-qualified object with a C23 constexpr object whose compile-time value is fixed. section 5.6.1
