c program static_assert() char bit=16

Question

What is CHAR_BIT==16 means in this code? It doesn't compile, I can not figure out the reason and what will be in puts so code will compile?

    #include <stdio.h>
    #include <stdlib.h>
    #include <assert.h>
    static_assert(CHAR_BIT==16,"16 bit falsely assumed");
    int main()
    {
        puts("hello world this");
        return 0;
    }

If you found static_assert(CHAR_BIT==16, ...); in some code, there should be some hints as to why that check is done somewhere close to where you found that assertion. — Ted Lyngmo
– Ted Lyngmo, Commented Mar 11, 2022 at 13:57
@dbush Yey! _Static_assert (and static_assert via a macro in assert.h I suppose) - Wow, that made my day. I've wanted that many times but just assumed ... stoopid me. Many thanks! — Ted Lyngmo
– Ted Lyngmo, Commented Mar 11, 2022 at 14:02

Sourav Ghosh · Accepted Answer · 2022-03-11 14:01:18Z

4

CHAR_BIT is a Macro defined in limits.h. It mentions the number of bits in a char. Most systems use 8 bits, but there are architectures with less (7 bits) or more.

In your code, the assert is checking, if the system is using 16 bits for a char, then only the code will compile.

Note: Based on your compiler version and support, you may need to use _Static_assert instead.

edited Mar 11, 2022 at 14:01

answered Mar 11, 2022 at 13:54

Sourav Ghosh

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2 Comments

Eric Postpischil Over a year ago

There are no C implementations that conform to the C standard where CHAR_BIT is 7. C 2018 5.2.4.2.1 1 requires it be at least 8.

Sourav Ghosh Over a year ago

@EricPostpischil agree, what I meant is there are systems with bytes using 7 bits (not necessarily conforming).

Eric Postpischil · Accepted Answer · 2022-03-11 14:14:11Z

2

CHAR_BIT is defined in <limits.h>. You need to include it for your code to compile.

edited Mar 11, 2022 at 14:14

Eric Postpischil

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answered Mar 11, 2022 at 13:54

Gnqz

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1 Comment

DevSolar Over a year ago

...but even then CHAR_BIT is hugely unlikely to be 16. If it is, I would love to hear about the OP's platform.

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