Very Computer

#include <stdio.h>

int
main(void)
{
        int     i;;             /* XXX */
        int     another;

        i = another = 0;

        return 0;

Quote:}

I guess that the error message "b.c:7: parse error before `int'" is due
to the facts that 'a null statement', that is, ';', is immediately
followed by another declaration "int another;", and that in my knowledge,
declarations must precede any statements in C.

But I could not explain these things to others in the view points of the
ANSI C standard, mainly because I have never read the C standard.  So I beg
you to explain me the real meaning of the above error message ""b.c:7: parse
error before `int'"" in the words of ANSI C standard, or if possible,
by the words of the ANSI C draft.

Please consider my embarrassing situation.  I talked to my friends that
"The one who can not catch an error in the aboce C program on sight
should not be considered as a C expert."  Is there any lines that
are similar to "A statement should not be followed by a declaration"
in ANSI C standard or 'the New Testament'?

=======
Don't reply privately.  My email system has some problems Now.

# #include <stdio.h>

# int
# main(void)
# {
#         int     i;;             /* XXX */
#         int     another;

#         i = another = 0;

#         return 0;
# }

...
# But I could not explain these things to others in the view points of the
# ANSI C standard, mainly because I have never read the C standard.  So I beg
# you to explain me the real meaning of the above error message ""b.c:7: parse
# error before `int'"" in the words of ANSI C standard, or if possible,
# by the words of the ANSI C draft.

It's a matter of grammar. In ISO 9899 6.6.2 a compound statement is
defined as:

compound-statement:
        '{' declaration-list(optional)  statement-list(optional) '}'

"int i;" fits the declaration-list, the next ";" fits only statement-list.
There is no way the C grammar could allow "int another;" following.
So it's a syntax error which *has to be* diagnosed by the translator.

Tell that to your friends; they should RTFS :-)

Regards,

        Jens
--
Jens Schweikhardt  http://www.shuttle.de/schweikh/
SIGSIG -- signature too long (core dumped)

        compound-statement:
                { declaration-list[opt] statement-list[opt] }

        declaration-list:
                declaration
                declaration-list declaration

        statement-list:
                statement
                statement-list statement

The specifies that there must not be any declarations after a
statement. Now, let's take alook at the definition of a statement:

6.6.3 Expression and null statements

        Syntax

                expression-statement:
                        expression[opt] ;

        Semantics
                The expression in an expression statement is evaluated
                as a void expression for its side effects.

                A *null statement* (consisting of just a semicolon)
                performs no operations.

I think this speaks for itself. A null statement is a legal statement,
and according to 6.6.2 there may be no declarations after the first
statement.

Hope this helps.

--
Elias Martenson
elias.martenson (atsign) sweden.sun.com

: #include <stdio.h>

: int
: main(void)
: {
:         int     i;;             /* XXX */
:         int     another;
:         i = another = 0;
:         return 0;
: }

: =======
: I know that if I compile above program, my C compiler will give me an error
: message, and I know that I should not give TWO ';'s after the 'int i'.

: I guess that the error message "b.c:7: parse error before `int'" is due
: to the facts that 'a null statement', that is, ';', is immediately
: followed by another declaration "int another;", and that in my knowledge,
: declarations must precede any statements in C.

Yes.  That's why 'int main(void) { int i; ; i = 0; return 0; }' will
work, or at least not produce complaints.

Will

Quote:>        int     i;;             /* XXX */
>        int     another;
>I guess that the error message "b.c:7: parse error before `int'" is due
>to the facts that 'a null statement', that is, ';', is immediately
>followed by another declaration "int another;", and that in my knowledge,
>declarations must precede any statements in C.

For example, a top-down compiler will get to the second "int" and find
there's no construct that can begin with it. So it reports something
like "parse error" or "'int' not valid in this context". A bottom-up
compiler will convert this into:

    { declaration statement declaration }

and then find no construct that matches this, so it will say something
like "statement cannot be followed by declaration".

Quote:>But I could not explain these things to others in the view points of the
>ANSI C standard, mainly because I have never read the C standard.  So I beg
>you to explain me the real meaning of the above error message ""b.c:7: parse
>error before `int'"" in the words of ANSI C standard, or if possible,
>by the words of the ANSI C draft.

    block:
        { dec-list-opt stat-list-opt }

    dec-list:
        declaration
        dec-list declaration

    stat-list:
        statement
        stat-list statement

There is no way to have a statement followed by a declaration using
those rules.

The phrase "parse error" usually means "you have a sequence of tokens
that can't be generated by the syntax in the Standard".

Quote:>Is there any lines that
>are similar to "A statement should not be followed by a declaration"
>in ANSI C standard

The point is moot in C9X, because we *do* now allow statements and
declarations to be randomly mixed.

--


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Written on my laptop; please observe the Reply-To address

Of course C89 conforming implementations couldn't keep silent about it.

--
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