Question

I have the following code:

do
{
    doStuffP1();
    if (test)
    {    goto skip_increment;
    }
    dostuffP2();

    skip_increment:
    // 1;  // Only works if I remove the comment at line start.
} while (loop);

Which doesn’t compile (VC++ 2010) with this error:

file_system_helpers.cpp(109) : error C2143: syntax error : missing ';' before '}'

If I change it to:

skip_increment:

1;

It compiles (and works).

Is this really a limitation of C++ syntax?

Answer 1

I assume the “1;” was supposed to be missing from your first code snippet?

Look at this grammar here: http://www.lysator.liu.se/c/ANSI-C-grammar-y.html

This defines labels only as a “labeled-statement”. That is, a block body can contain label: <statement> anywhere in its sequence of contents, but the statement after the label is not optional. So this would make skip_increment: } invalid.

(And, OK, you’re using C++ and not C; but I doubt if making allowances for extra uses of goto was something anyone cared much about while defining the C++ language.)