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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Octal
Date: Wed, 28 Dec 2016 09:31:40 -0800
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BartC <bc@freeuk.com> writes:
[...]
> But if a compiler is going to think up ways that a programmer may have 
> written numbers wrongly then what about:
>
>   0x123E3
>
> Maybe /this/ should have been written as 0x123p3!
>
> Or 123E3, which was supposed to be 0x123E3 but the the "0x" was left 
> out. Or 0123E3, when the "x" is left out.
>
> Why is the compiler not giving errors in these cases? Surely they must 
> count as pp-numbers too.

0x123E3 is a perfectly valid hexadecimal integer constant.  123E3 is a
perfectly valid floating constant.  Yes, they're valid pp-numbers, and
they're converted to valid constants in translation phase 7.  That's why
compilers don't print error messages for them -- because they're not
errors.

I've already explained why 0x123e+3 is a syntax error.  I understand
that you don't like that fact; I'm not entirely pleased about it myself.
But it is what it is.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"