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SubjectRe: Patch to remove undefined C code


On 16 Oct 2000, Ben Pfaff wrote:

> Jonathan George <Jonathan.George@trcinc.com> writes:
>
> > This patch has many bogus corrections where new variables were created, but
> > the order of evaluation is already unambiguous.
> >
> > For example each comma separated clause in an expression is guaranteed to be
> > completely evaluated before the next comma separated clause Including
> > Assignments.
>
> No, that is not true in general. When the comma in question is
> the comma operator, it is true. But when the comma separates
> arguments to a function, it is not: the order of evaluation of
> function arguments is implementation dependent. See C89 section
> 6.3.2.2 "Function calls":
[snip]

No arguments here, but proposed fixes were remarkably ugly. Example:

tmp = *p++;
*q = f(tmp, *p++);
return p;

is equivalent to more idiomatic

*q = f(p[0], p[1]);
return p+2;

And example with copying the string up to the comma... Yuck. Legal C !=
decent C.

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