Re: [PATCH next v4 0/5] minmax: Relax type checks in min() and max().

[Linus Torvalds]

On Mon, 8 Jan 2024 at 03:46, Jiri Slaby <jirislaby@xxxxxxxxx> wrote:
>
>    CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
> real    0m45,002s
>
> $ git revert 867046cc7027703f60a46339ffde91a1970f2901
>    CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
> real    0m11,132s
>
> $ git revert 4ead534fba42fc4fd41163297528d2aa731cd121
>    CPP [M] drivers/media/pci/solo6x10/solo6x10-p2m.i
> real    0m3,711s

Ouch. Yeah, that's unfortunate. There's a lot of nested nasty macro
expansion there, but that timing is excessive.

Sparse actually complains about that file:

  drivers/media/pci/solo6x10/solo6x10-p2m.c:309:13: error: too long
token expansion
  drivers/media/pci/solo6x10/solo6x10-p2m.c:310:17: error: too long
token expansion

and while that is a sparse limitation, it's still interesting. Having
that file expand to 122M is not ok.

In this case, I suspect the right thing to do is to simply not use
min()/max() in that header at all, but do something like

  --- a/drivers/media/pci/solo6x10/solo6x10-offsets.h
  +++ b/drivers/media/pci/solo6x10/solo6x10-offsets.h
  @@ -56,2 +56,5 @@

  +#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
  +#define MAX(X, Y) ((X) > (Y) ? (X) : (Y))
  +
   #define SOLO_MP4E_EXT_ADDR(__solo) \
  @@ -59,4 +62,4 @@
   #define SOLO_MP4E_EXT_SIZE(__solo) \
  -     max((..),                               \
  -         min(((..) - \
  +     MAX((..),                               \
  +         MIN(((..) - \
                 ..), 0x00ff0000))
  @@ -67,4 +70,4 @@
   #define SOLO_JPEG_EXT_SIZE(__solo) \
  -     max(..,                         \
  -         min(..)
  +     MAX(..,                         \
  +         MIN(..)

and avoid this issue.

That said, I'm sure this thing exists to a smaller degree elsewhere. I
wonder if we could simplify our min/max type tests..

             Linus