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)

1 files changed, 14 insertions, 0 deletions

diff --git a/coccinelle/take-ptr.cocci b/coccinelle/take-ptr.cocci
new file mode 100644
index 0000000000..0cebe81575
--- /dev/null
+++ b/coccinelle/take-ptr.cocci
@@ -0,0 +1,14 @@
+@@
+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);