std::string::npos value is not -1

Question

It's been said in this doc http://www.cplusplus.com/reference/string/string/npos/ that std::string::npos is -1. But when I print out the value, it's not. Is this value architecture dependent?

My test is very simple

std::cout << std::string::npos << std::endl;

which outputs

4294967295

Answer 1

From the link you've given:

This constant is defined with a value of -1, which because size_t is an unsigned integral type, it is the largest possible representable value for this type.

Answer 2

This constant is defined with a value of -1, which because size_t is an unsigned integral type, it is the largest possible representable value for this type.

they say an unsigned integral type

Answer 3

To add to the other answers trying outputting the result of (size_t)-1 . You can verify that this value is the same as std::string::npos .

Answer 4

According to the C++ Standard data member npos of standard class std::basic_string is declared the following way

static const size_type npos = -1;

On the other hand type name size_type corresponds to some unsigned integral type. So what you got is the internal representation of -1 interpreted as unsigned value. This means that the sign bit was considered as a value bit.