systemd/coccinelle/take-ptr.cocci
Lennart Poettering ae2a15bc14 macro: introduce TAKE_PTR() macro
This macro will read a pointer of any type, return it, and set the
pointer to NULL. This is useful as an explicit concept of passing
ownership of a memory area between pointers.

This takes inspiration from Rust:

https://doc.rust-lang.org/std/option/enum.Option.html#method.take

and was suggested by Alan Jenkins (@sourcejedi).

It drops ~160 lines of code from our codebase, which makes me like it.
Also, I think it clarifies passing of ownership, and thus helps
readability a bit (at least for the initiated who know the new macro)
2018-03-22 20:21:42 +01:00

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@@
local idexpression p;
expression q;
@@
- p = q;
- q = NULL;
- return p;
+ return TAKE_PTR(q);
@@
expression p, q;
@@
- p = q;
- q = NULL;
+ p = TAKE_PTR(q);