Const text variable declaration C

Question

Just a quick question for which I fail in finding proper answer.

If I want to declare a const text variable, is it absolutely equal to do:

const char my_variable [] = {'t', 'e', 's', 't', 0};

or

const char my_variable [] = "test";

Many thanks in advance

Yes, these are equivalent. Just make sure to make the distinctions as in my older question — Eugene Sh.
– Eugene Sh., Commented Feb 1, 2018 at 16:01
Since the character array is constant I would instead define const char *my_variable = "test"; — August Karlstrom
– August Karlstrom, Commented Feb 1, 2018 at 16:27
@AugustKarlstrom There are different usecases. Note the difference in behavior when using sizeof, for example. — Eugene Sh.
– Eugene Sh., Commented Feb 1, 2018 at 16:31
@EugeneSh. That's true, sizeof is more efficient than strlen. — August Karlstrom
– August Karlstrom, Commented Feb 1, 2018 at 16:52

Bathsheba · Accepted Answer · 2018-02-01 16:11:40Z

5

Yes, the two declarations are identical.

"test" is a char[5] type in C, with elements 't', 'e', 's', 't', and 0.

(Note that in C++, the type is a const char[5]: yet another difference between the two languages. See What is the type of string literals in C and C++?).

edited Feb 1, 2018 at 16:11

answered Feb 1, 2018 at 16:01

Bathsheba

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7 Comments

ad absurdum Over a year ago

The characters of a string literal are stored (in static storage) in arrays of type char, not const char, so "test" is a char[5] type, but it is UB to attempt to modify it.

Bathsheba Over a year ago

@DavidBowling: Oops. Yet another difference between C and C++.

ad absurdum Over a year ago

Oh yeah, I forgot that this is one of the things that C++ got right ;)

Bathsheba Over a year ago

@DavidBowling: But they ruined the language with a bool type!

Bathsheba Over a year ago

@EugeneSh. One issue is that things like (a == b) + (b == c) is an int in C and C++, but a == b is a bool in C++. C is a model of consistency in this respect.

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user2736738 · Accepted Answer · 2018-02-01 16:18:26Z

2

From standard 6.7.9p14: (Supporting the other answer)

An array of character type may be initialized by a character string literal or UTF-8 string literal, optionally enclosed in braces. Successive bytes of the string literal (including the terminating null character if there is room or if the array is of unknown size) initialize the elements of the array.

So yes both of them are achieving the same thing.

answered Feb 1, 2018 at 16:18

user2736738

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