From 4463087223983c40a6d67beab0513fba7cdb7538 Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Wed, 16 Dec 2020 15:59:58 +0100
Subject: BLI: remove implicit casts between some span types

Casting pointers from one type to another does change the
value of the pointer in some cases. Therefore, casting a span
that contains pointers of one type to a span that contains
pointers of another type, is not generally safe. In practice, this
issue mainly comes up when dealing with classes that have a
vtable.

There are some special cases that are still allowed. For example,
adding const to the pointer does not change the address.
Also, casting to a void pointer is fine.

In cases where implicit conversion is disabled, but one is sure
that the cast is valid, an explicit call of `span.cast<NewType>()`
can be used.
---
 source/blender/blenlib/tests/BLI_memory_utils_test.cc | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'source/blender/blenlib/tests/BLI_memory_utils_test.cc')

diff --git a/source/blender/blenlib/tests/BLI_memory_utils_test.cc b/source/blender/blenlib/tests/BLI_memory_utils_test.cc
index fcef2f8688a..23415e69b04 100644
--- a/source/blender/blenlib/tests/BLI_memory_utils_test.cc
+++ b/source/blender/blenlib/tests/BLI_memory_utils_test.cc
@@ -158,4 +158,15 @@ static_assert(is_convertible_pointer_v<int **, int **const>);
 static_assert(is_convertible_pointer_v<int **, int *const *>);
 static_assert(is_convertible_pointer_v<int **, int const *const *>);
 
+static_assert(is_span_convertible_pointer_v<int *, int *>);
+static_assert(is_span_convertible_pointer_v<int *, const int *>);
+static_assert(!is_span_convertible_pointer_v<const int *, int *>);
+static_assert(is_span_convertible_pointer_v<const int *, const int *>);
+static_assert(is_span_convertible_pointer_v<const int *, const void *>);
+static_assert(!is_span_convertible_pointer_v<const int *, void *>);
+static_assert(is_span_convertible_pointer_v<int *, void *>);
+static_assert(is_span_convertible_pointer_v<int *, const void *>);
+static_assert(!is_span_convertible_pointer_v<TestBaseClass *, TestChildClass *>);
+static_assert(!is_span_convertible_pointer_v<TestChildClass *, TestBaseClass *>);
+
 }  // namespace blender::tests
-- 
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