On Wed, 2023-07-26 at 17:43 +0200, Jan Beulich wrote:
> On 26.07.2023 17:28, Oleksii wrote:
> > On Mon, 2023-07-10 at 10:58 +0200, Jan Beulich wrote:
> > > On 10.07.2023 10:56, Jan Beulich wrote:
> > > > Use the generic framework in xen/linkage.h. No change in
> > > > generated
> > > > code
> > > > except of course the converted symbols change to be hidden ones
> > > > and
> > > > gain
> > > > a valid size.
> > > >
> > > > Signed-off-by: Jan Beulich <jbeul...@suse.com>
> > >
> > > I'm sorry, the Cc list was incomplete here. Adding back the
> > > remaining
> > > REST
> > > maintainers.
> > >
> > > Jan
> > >
> > > > ---
> > > > Probably count_args_exp() should move to macros.h, but I first
> > > > wanted to
> > > > see whether anyone can suggest any better approach for checking
> > > > whether
> > > > a defined macro expands to nothing.
> > What about introduction of conditional macros ?
> > Something similar to:
> > #include <stdio.h>
> >
> > #define CONDITIONAL_RETURN(arg1, arg2)
> > CONDITIONAL_RETURN_IMPL(arg1,
> > arg2, EMPTY)
> >
> > #define EMPTY(...) ""
> >
> > #define CONDITIONAL_RETURN_IMPL(arg1, arg2, empty_check) \
> > CONDITIONAL_RETURN_##empty_check(arg1, arg2)
> >
> > #define CONDITIONAL_RETURN_EMPTY(arg1, arg2) \
> > CONDITIONAL_RETURN_ARG1(arg1, arg2)
> >
> > #define CONDITIONAL_RETURN_ARG1(arg1, arg2) arg1, arg2
> >
> > #define CONDITIONAL_RETURN_ARG2(arg1, arg2) arg1
>
> I don't see how this would be used in your scheme. It ...
>
> > int main() {
> > int a = 42;
> > const char* b = "hello";
> >
> > // Second argument is not empty, both arguments are returned
> > printf("Case 1: %d, %s\n", CONDITIONAL_RETURN(a, b)); //
> > Prints:
> > Case 1: 42, hello
> >
> > // Second argument is empty, only the first argument is
> > returned
> > printf("Case 2: %d, %s\n", CONDITIONAL_RETURN(a, "")); //
> > Prints:
> > Case 2: 42,
>
> ... certainly isn't here, or this likely would cause at least a
> warning
> from the compiler (for there being too few arguments to printf()) and
> then a runtime UB for interpreting something as a pointer to a string
> which likely isn't.
>
> > return 0;
> > }
> >
> > and then define DO_CODE_ALIGN using CONDITIONAL_RETURN?
>
> Afaict instead of getting rid of the comma, you'd actually add ""
> after it. What am I missing?
You are right. I missed that actually it returns "".
~ Oleksii
