Weirdness in parsing cpp macros

[Julia Lawall]

On Wed, 20 Mar 2024, Ville Syrjälä wrote:

> Hi Julia et al,
>
> In Linux drm/i915 driver (drivers/gpu/drm/i915/display/intel_pps.[ch])
> we have a magic macro like this:
>
> #define with_intel_pps_lock(dp, wf) \

Did you try declaring:

iterator name with_intel_pps_lock;

up with the metavariables?

julia


>         for ((wf) = intel_pps_lock(dp); (wf); (wf) = intel_pps_unlock((dp), (wf)))
>
>
> which we can then use like so:
> ...
> with_intel_pps_lock(intel_dp, wakeref)
> 	wait_panel_power_cycle(intel_dp);
> ...
>
>
> If I try to modify this code with eg.
>
> @@
> @@
> - wait_panel_power_cycle
> + _wait_panel_power_cycle
>
> spatch fails to parse the macro and won't do the changes here.
>
>
> While experimenting with this I discovered that
> I can make it work by:
> - moving the macro definition into intel_pps.c file from intel_pps.h
> - renaming the macro to contain the substring "for" (doesn't matter
>   where in the macro name the "for" appears)
>
> What on earth is going on here?
>
> --
> Ville Syrjälä
> Intel
>