Re: [PATCH v8 2/5] cifs: Autogenerate SMB2 error mapping table

[ChenXiaoSong <chenxiaosong.chenxiaosong@linux.dev>]

I am concerned that X macros may make the code harder to read. What do 
others think?

Thanks,
ChenXiaoSong <chenxiaosong@kylinos.cn>

On 1/16/26 21:48, Aurélien Aptel wrote:
> May I suggest using X macros?
> you don't need pre-processing and generation of files and you can keep
> as much metadata as you want in the macro at zero runtime cost and
> build what you need.
> 
> You can have one .h file like this:
> 
> #define SMB2_ERR_LIST \
>   X(STATUS_WAIT_1, 0x00000000, -EIO, <whatever else>) \
>   X(STATUS_WAIT_2, 0x00000001, -EIO, <whatever else>) \
> ...
> 
> and then do things like:
> 
> enum smb2_error {
> #define X(code, val, ...) code = cpu_to_le32(val),
> SMB2_ERR_LIST
> #undef X
> };
> 
> Might have to use typed enum to get the le32 through
>   https://gcc.gnu.org/onlinedocs/gcc/Enum-Extensions.html
> 
> struct smb2_errno_map { le32 code; const char *name; int errno; };
> struct smb2_errno_map smb2_to_errno[] = {
> #define X(name, val, errno, ...) {cpu_to_le32(val), #name, errno},
> SMB2_ERR_LIST
> #undef X
> };
> 
> Also you can use bsearch() to do log(N) lookup. But maybe the compiler
> optimizes a larger switch to the same thing already.
> 
> static int cmp_smb2_err(const void *key, const void *elt)
> {
>      return *(const enum smb2_error *)key - ((const struct
> smb2_errno_map *)elt)->val;
> }
> 
> int smb2_err_lookup(enum smb2_error err)
> {
>      struct smb2_errno_map *res = bsearch(&err, smb2_to_errno,
> ARRAY_SIZE(smb2_to_errno), sizeof(smb2_to_errno[0]), cmp_smb2_err);
>      ...
> }
> 
> 
> (code untested)