CODEWITHSUNDEEP
c++stringliteralsstring-literals
Vihaan Verma
Vihaan Verma

Reputation: 13143

What is the type of a string literal?

I'm confused about the type of a string literal. Is it a const char * or a const char?

Upvotes: 25

Views: 4062

Answers (3)

Jan Schultke
Jan Schultke

Reputation: 39415

Ordinary string literals are of type const char[n], i.e. "array of n const char", where n is the number of characters in the string, including the null terminator. For example, the string literal "foo" is an lvalue of type const char[4] (n is 4 due to the null terminator at the end of the string).

It would be valid to write:

const char* str = "foo";

... because of array-to-pointer conversion, but the type of "foo" is still const char[4].

There are other kinds of string literals with different types. Here is a comparison, taken from Table 12: String literals in the C++ standard:

Kind Type Example
ordinary string literal array of n const char "ordinary string"
wide string literal array of n const wchar_t L"wide string"
UTF-8 string literal array of n const char8_t u8"UTF-8 string"
UTF-16 string literal array of n const char16_t u16"UTF-16 string"
UTF-32 string literal array of n const char32_t u32"UTF-32 string"

Ordinary raw string literals are also of type const char[n]. For example, a raw UTF-8 string literal u8R"(raw)" is of type const char8_t[4].

Note on C++98 and C

In C++98, the type of string literals is non-const, same as in C. This behavior was deprecated in C++03 and the type was made const in C++11. However, string literals are non-const in C to this day.

For all intents and purposes, you should treat string literals as if they are const. Even if you're using an old version of C++, or you're using C, you are not allowed to modify the string, so adding an "unnecessary" const can prevent bugs.

Upvotes: 0

DevSolar
DevSolar

Reputation: 70213

"Hello world" is const char[12] (eleven characters plus '\0' terminator).

L"Hello world" is const wchar_t[12].

Since C++14, "Hello world"s is std::string.

Since C++17, "Hello world"sv is std::string_view.

Also note the u8"", u"" and U"" string literal notations added by C++11, which specify UTF-8, UTF-16 and UTF-32 encoding, respectively. The encoding of non-qualified string literals (i.e. "" and L"") is (and always was) implementation-defined.

Upvotes: 10

Seth Carnegie
Seth Carnegie

Reputation: 75130

It is a const char[N] (which is the same thing as char const[N]), where N is the length of the string plus one for the terminating NUL (or just the length of the string if you define "length of a string" as already including the NUL).

This is why you can do sizeof("hello") - 1 to get the number of characters in the string (including any embedded NULs); if it was a pointer, it wouldn't work because it would always be the size of pointer on your system (minus one).

Upvotes: 32

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