rust: init: wrap type checking struct initializers in a closure

In the implementation of the init macros there is a `if false` statement
that type checks the initializer to ensure every field is initialized.
Since the next patch has a stack variable to store the struct, the
function might allocate too much memory on debug builds. Putting the
struct into a closure ensures that even in debug builds no stack
overflow error is caused. In release builds this was not a problem since
the code was optimized away due to the `if false`.

Signed-off-by: Benno Lossin <[email protected]>

Author: BennoLossin

rust/kernel/init.rs

@@ -641,14 +641,16 @@ macro_rules! try_pin_init {
                     // We use unreachable code to ensure that all fields have been mentioned exactly
                     // once, this struct initializer will still be type-checked and complain with a
                     // very natural error message if a field is forgotten/mentioned more than once.
-                    #[allow(unreachable_code, clippy::diverging_sub_expression)]
+                    #[allow(unreachable_code, clippy::diverging_sub_expression, clippy::redundant_closure_call)]
                     if false {
-                        $crate::try_pin_init!(make_initializer:
-                            @slot(slot),
-                            @type_name($t),
-                            @munch_fields($($fields)*,),
-                            @acc(),
-                        );
+                        (|| {
+                            $crate::try_pin_init!(make_initializer:
+                                @slot(slot),
+                                @type_name($t),
+                                @munch_fields($($fields)*,),
+                                @acc(),
+                            );
+                        })();
                     }
                 }
                 Ok(__InitOk)
@@ -889,14 +891,16 @@ macro_rules! try_init {
                     // We use unreachable code to ensure that all fields have been mentioned exactly
                     // once, this struct initializer will still be type-checked and complain with a
                     // very natural error message if a field is forgotten/mentioned more than once.
-                    #[allow(unreachable_code, clippy::diverging_sub_expression)]
+                    #[allow(unreachable_code, clippy::diverging_sub_expression, clippy::redundant_closure_call)]
                     if false {
-                        $crate::try_init!(make_initializer:
-                            @slot(slot),
-                            @type_name($t),
-                            @munch_fields($($fields)*,),
-                            @acc(),
-                        );
+                        (|| {
+                            $crate::try_init!(make_initializer:
+                                @slot(slot),
+                                @type_name($t),
+                                @munch_fields($($fields)*,),
+                                @acc(),
+                            );
+                        })();
                     }
                 }
                 Ok(__InitOk)