Re: sizeof(x)

On Sun, 30 Mar 2008 23:07:05 +0300, Ioannis Vranos wrote:
Harald van Dijk wrote:
On Sun, 30 Mar 2008 22:50:00 +0300, Ioannis Vranos wrote:
In C99 it is mentioned:

"The sizeof operator yields the size (in bytes) of its operand, which
may be an expression or the parenthesized name of a type.".

If I am not wrong, this implies that

int x;

size_t y= sizeof(x);


is not valid.

You are; (x) is a perfectly valid expression, so there's no problem
taking the size of (x).

I first saw that only sizeof x is valid at the pdf hosted at
http://cprog.tomsweb.net.

That doesn't say sizeof(x) is invalid any more than the standard does.

Then I checked the C99 standard and it mentions what is shown above.
Clearly C99 doesn't mention parenthesized expression.

Yes, it does. Look at the grammar.

unary-expression:
sizeof unary-expression

unary-expression:
postfix-expression

postfix-expression:
primary-expression

primary-expression:
( expression )

A parenthesised expression is a primary-expression, which is a postfix-
expression, which is a unary-expression, which is a valid operand of
sizeof.

The standard doesn't explicitly mention that parenthesised expressions
are valid operands of +, -, *, /, ^, &, or pretty much any other
operator. The grammar makes that clear already.
.

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