'do {} while (0)' replacement

[Richard Harvey Chapman]

Frank,

This is just a philosophical question, right? Because it seems to me 
that there are other ways to accomplish this task which are easier. But 
in the interest of brain teasers...


Frank Mehnert wrote:
> This changes the semantics: The BREAK_ON_ERROR() macro should be
> handled as one compound statement. The following statement should
> work as well:
>
>   if (bar)
>     BREAK_ON_ERROR(buzz);
>   else
>     BREAK_ON_ERROR(buzz1);
>
Well, this is different than what you originally stated. In this case, 
your macro will compile without warning. My quick suggestion would then be:

    if (bar)
      BREAK_ON_ERROR(buzz);
    else
      BREAK_ON_ERROR(buzz);

    if (bar)
      BREAK_ON_ERROR_NO_ELSE(buzz);

where BREAK_ON_ERROR_NO_ELSE is the modified macro without the "else". 
This also has the added benefit that if either macro is used in the 
wrong situation, the compiler will issue an error.

However, if we're really trying to find a single macro for this, I do 
not think it is possible. The reasoning follows that the whole point of 
do{ statement(s) }while(0) is to avoid the syntax error about the 
semicolon placed at the end of the macro. The only way in C to construct 
a compound statement is with braces, { and }, which will generate the 
semicolon syntax error that you're trying to avoid (if placed between an 
"if" and an "else").

Regards,

Harvey