Re: "A diagram of C23 basic types"

On 08/05/2025 16:09, Waldek Hebisch wrote:

Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:

Michael S <already5chosen@yahoo.com> writes:
>

On Mon, 14 Apr 2025 01:24:49 -0700
Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:
>

about where they may or may not be used.  Do you really have a
problem avoiding identifiers defined in this or that library
header, either for all headers or just those headers required for
freestanding implementations?

>
I don't know.  In order to know I'd have to include all
standard headers into all of my C files

>
Let me ask the question differently.  Have you ever run into an
actual problem due to inadvertent collision with a reserved
identifier?

 Not in my own code.  But I remember an old piece of code whose
author apparently thought that 'inline' is a perfect name for
input line.  Few days ago I had trouble compiling with gcc-15
code which declares its own 'bool' type.  The code is supposed to
compile using a wide range of compilers, so I am still looking
for "best" solution.
 

gcc changed the default standard to "gnu23" in gcc15, from "gnu17" in earlier versions.  Their policy is that unless you specify the standard explicitly, you get the latest C standard that is well-supported by gcc, along with the common gcc extensions.  (New ISO C standards supersede older ones - thus "C" means "C23" at the moment.)
And in C23, "bool", "true" and "false" are now keywords.  The boolean type was renamed "bool" with "_Bool" being an alias for compatibility. C23 has more backwards incompatible changes than usual for C standards since C99.  (Personally, I am happy to see such changes - people have had a generation to get used to C booleans - but I fully understand that does not apply to everyone or all code.)
The "best" solution, IMHO, is that you should never use a C compiler for serious work without specifying the standard you are using.  (And if the C compiler doesn't let you choose the standard, consider whether it is actually a suitable tool for serious work.)  If you decide that you want C23, with or without gcc extensions, you will need to fix that ancient code to remove or rename its home-made "bool" type.  If you want to keep the code unchanged, pick an appropriate older C standard.  (You will also want to do that if you want to be able to compile the code with older gcc versions or other compilers that don't yet support C23.)