On Sun, 5 Jan 2025 15:14:22 +0100
Oleg Nesterov <o...@redhat.com> wrote:
> Masami,
>
> Sorry for abusing this thread. Your patches look fine to me, it is not
> that I suggest to change them. I will use your patch as an example for
> off-topic discussion.
>
> On 01/05, Masami Hiramatsu (Google) wrote:
> >
> > +DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
>
> (IS_ERR looks unneeded but this is cosmetic).
>
> OK, so it can be used as
>
> void func(void)
> {
> char **argv __free(argv) = argv_split(...);
> do_something(argv);
> return;
> }
>
> And I cry every time when I read the code like this ;)
>
> Because, to understand this code, I need to do the "nontrivial" grep to find
> "DEFINE_FREE(argv,".
>
> Perhaps we can establish a simple rule that every DEFINE_FREE() or
> DEFINE_CLASS()
> should add another #define? I mean something like
>
>
> DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> #define __FREE_ARGV __free(argv)
>
> void func(void)
> {
> char **argv __FREE_ARGV = argv_split(...);
> do_something(argv);
> return;
> }
>
> This way I can press Ctrl-] and see what the cleanup code actually does.
> Can save a second or two. Important when you try to read the code you are
> not familiar with.
That sounds lile a problem of your tool. Do you really need to find the
DEFINE_FREE() or do you think "__free(argv)" is too generic name?
If it is latter, we can make it "__free(argv_free) so that it is more
obvious to call argv_free()?
>
> Same for DEFINE_CLASS. For example,
>
> int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
> {
> CLASS(fd, f)(fd);
>
> if (fd_empty(f))
> return -EBADF;
>
> return vfs_fchown(fd_file(f), user, group);
> }
>
> If you are not familiar with this code, it looks mysterious until you find
> DEFINE_CLASS(fd, ...) in include/linux/file.h.
DEFINE_CLASS() is somewhat mysterious to me too :) But if I understand
correctly, it is for intermediate macro for implementing guard().
Whether we like it or not, cleanup.h has been introduced, and it will be
more popular. What we need is a document about cleanup.h which includes
better naming conventions for its label.
BTW, I agree that 'argv' was too simple. Basically the label name of
DEFINE_FREE() is better to be a function name for free.
Let me fix that.
Thank you,
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
