Revisiting generalized lvalues

[Florian Weimer]

* Michael Krasnik:

> #ifdef  PRODUCTION
> #define X_ABC(x)       ( check( x ), x->abc )
> #else
> #define X_ABC(x)        x->abc
> #endif
>
> which expands
>
>     X_ABC(x) = y;
>
> to:
>
>     ( check( x ), x->abc ) = y;

> Eliminating this construct makes macros much less flexible
> and requires much more work for creating self-verifying
> frameworks, which is a big issue for small companies with
> large codebase.

There seems to be a trivial fix: modifiy the check function to return
its argument.