From db24ef20ee02279aba441019482b506352b3af75 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 14 Jul 2019 09:19:18 +0200
Subject: [PATCH] explain let_base_ptr

---
 src/offset_of.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/offset_of.rs b/src/offset_of.rs
index 98e7644..a1300af 100644
--- a/src/offset_of.rs
+++ b/src/offset_of.rs
@@ -26,6 +26,10 @@
 macro_rules! let_base_ptr {
     ($name:ident, $type:tt) => {
         // No UB here, and the pointer does not dangle, either.
+        // But we have to make sure that `uninit` lives long enough,
+        // so it has to be in the same scope as `$name`. That's why
+        // `let_base_ptr` declares a variable (several, actually)
+        // instad of returning one.
         let uninit = $crate::mem::MaybeUninit::<$type>::uninit();
         let $name = uninit.as_ptr();
     };