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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: CHAR_BIT is not eight
Date: Wed, 12 Oct 2022 17:16:37 -0700
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Frederick Virchanza Gotham <cauldwell.thomas@gmail.com> writes:
> Since I started programming in C/C++ back in the early 2000's, I never
> encountered a compiler with CHAR_BIT anything other than 8.
>
> Well just now in the past 15 minutes, I was trying to get the code for
> the 'base58' algorithm to compile for the Texas Instruments F2809
> microcontroller using the 'cl2000' compiler.
>
> At first I was puzzled as to why 'sizeof(long)' was coming back as
> 2. Of course my first assumption here was that 'long' was 16-Bit (even
> though the Standard says that a 'long' must be at least 32-Bit). So I
> figured that this compiler was just non-standard-compliant on a few
> issues.
>
> After a little messing around, I realised that CHAR_BIT is 16.
>
> I looked through the compiler manual and found this paragraph:
>
> "By ANSI/ISO C definition, the sizeof operator yields the number of
> bytes required to store an object. ANSI/ISO further stipulates that
> when sizeof is applied to char, the result is 1. Since the TMS320C28x
> char is 16 bits (to make it separately addressable), a byte is also 16
> bits. This yields results you may not expect; for example, size of
> (int) = = 1 (not 2). TMS320C28x bytes and words are equivalent (16
> bits). To access data in increments of 8 bits, use the __byte() and
> __mov_byte() intrinsics described in Section 7.6"
>
> So there you go: There are C++ compilers in use today in the year 2022
> with CHAR_BIT something other than 8.

Apparently the TMS320C28x is a DSP (Digital Signal Processor).  I've
heard that it's common for CHAR_BIT to be 16 or 32 in implementations
for DSPs.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */