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.
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