Re: [PATCH v2 0/2] Lock and Pointer guards

Rasmus Villemoes
2023-06-09T08:30:00Z

On 08/06/2023 17.45, Linus Torvalds wrote:

> And no, I didn't think too much about those names. "__automatic_kfree"
> is too damn long to type, but you hated "auto". And "no_free_ptr()" is
> not wonderful name either. But I tried to make the naming at least be
> obvious, if not wonderful.

No opinion either way, just throwing a data point out there:

So the systemd codebase makes quite heavy use of this automatic cleanup
stuff. Their name for no_free_ptr is TAKE_PTR(), and the verb "take"
apparently comes from Rust:

//// src/fundamental/macro-fundamental.h

/* Takes inspiration from Rust's Option::take() method: reads and
returns a pointer, but at the same time
* resets it to NULL. See:
https://doc.rust-lang.org/std/option/enum.Option.html#method.take */
#define TAKE_GENERIC(var, type, nullvalue) \
({ \
type *_pvar_ = &(var); \
type _var_ = *_pvar_; \
type _nullvalue_ = nullvalue; \
*_pvar_ = _nullvalue_; \
_var_; \
})
#define TAKE_PTR_TYPE(ptr, type) TAKE_GENERIC(ptr, type, NULL)
#define TAKE_PTR(ptr) TAKE_PTR_TYPE(ptr, typeof(ptr))
#define TAKE_STRUCT_TYPE(s, type) TAKE_GENERIC(s, type, {})
#define TAKE_STRUCT(s) TAKE_STRUCT_TYPE(s, typeof(s))

and then they also have a

/* Like TAKE_PTR() but for file descriptors, resetting them to -EBADF */
#define TAKE_FD(fd) TAKE_GENERIC(fd, int, -EBADF)

with their "auto-close fd" helper of course knowing to ignore any
negative value.

Rasmus