Re: Bart's Language

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

antispam@fricas.org (Waldek Hebisch) writes:
[...]
>

Well, it is rather easy to see if variable is used within its
own initialization, so practically it is minor gap.  Of course,
there is problem with C standard:  IIUC depending on rest of
the code declarations as above are merely undefined behaviour
or even produce unspecified value.  So C compiler is
forbidden to stop compilation are report compile time error.

>
Valid responses to undefined behavior include "terminating a translation
or execution (with the issuance of a diagnostic message)".

That's true, but doing so is allowed only if the circumstances
of undefined behavior have occurred.  In the case of compiling
a declaration such as

    int a = a;

no undefined behavior has as yet occurred.

In other
words, if a compiler is able to prove that a program has undefined
behavior (that will occur on each execution), it can reject it at
compile time.

The program can be rejected, but not because of the rule about
terminating a translation.  The program can be rejected because
the program is not strictly conforming, and implementations are
not required to accept programs that are not strictly conforming.