Re: [PATCH] bcachefs: Rename struct field swap to prevent macro naming collision

[Thorsten Blum]

On 6. Apr 2024, at 20:48, Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote:
> 
> On Sat, Apr 06, 2024 at 04:19:20PM +0200, Thorsten Blum wrote:
>> The struct field swap can collide with the swap() macro defined in
>> linux/minmax.h. Rename the struct field to prevent such collisions.
> 
> Same as in lib/sort.c, so what's the actual reason?

I included <linux/minmax.h> in arch/m68k/include/asm/bitops.h (to use the min()
macro), but received the following error:

fs/bcachefs/eytzinger.c: In function ‘do_swap’:
fs/bcachefs/eytzinger.c:128:69: error: macro "swap" passed 3 arguments, but takes just 2
  128 |                 ((const struct wrapper *)priv)->swap(a, b, (int)size);
      |                                                                     ^
In file included from ./arch/m68k/include/asm/bitops.h:16,
                 from ./include/linux/bitops.h:68,
                 from fs/bcachefs/eytzinger.h:5,
                 from fs/bcachefs/eytzinger.c:3:
/include/linux/minmax.h:270: note: macro "swap" defined here
  270 | #define swap(a, b) \
      |
fs/bcachefs/eytzinger.c:128:47: warning: statement with no effect [-Wunused-value]
  128 |                 ((const struct wrapper *)priv)->swap(a, b, (int)size);
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
make[4]: *** [scripts/Makefile.build:244: fs/bcachefs/eytzinger.o] Error 1
make[3]: *** [scripts/Makefile.build:485: fs/bcachefs] Error 2

I thought about using #undef swap, but renaming it seemed to be the least
disruptive change. Maybe there's a better solution?

Thanks,
Thorsten