diff options
author | Jacques Lucke <jacques@blender.org> | 2020-12-16 17:59:58 +0300 |
---|---|---|
committer | Jacques Lucke <jacques@blender.org> | 2020-12-16 18:00:17 +0300 |
commit | 4463087223983c40a6d67beab0513fba7cdb7538 (patch) | |
tree | f067cffc02bfb39fc4573615b3517b8e4cdcac65 /source/blender/blenlib/BLI_memory_utils.hh | |
parent | 684c771263db1a5a7dbf65cde97e672d94b57839 (diff) |
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.
Diffstat (limited to 'source/blender/blenlib/BLI_memory_utils.hh')
-rw-r--r-- | source/blender/blenlib/BLI_memory_utils.hh | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/source/blender/blenlib/BLI_memory_utils.hh b/source/blender/blenlib/BLI_memory_utils.hh index 49076bb1aae..b3b6855089e 100644 --- a/source/blender/blenlib/BLI_memory_utils.hh +++ b/source/blender/blenlib/BLI_memory_utils.hh @@ -428,6 +428,25 @@ inline constexpr bool is_convertible_pointer_v = std::is_convertible_v<From, To> &&std::is_pointer_v<From> &&std::is_pointer_v<To>; /** + * Helper variable that checks if a Span<From> can be converted to Span<To> safely, whereby From + * and To are pointers. Adding const and casting to a void pointer is allowed. + * Casting up and down a class hierarchy generally is not allowed, because this might change the + * pointer under some circumstances. + */ +template<typename From, typename To> +inline constexpr bool is_span_convertible_pointer_v = + /* Make sure we are working with pointers. */ + std::is_pointer_v<From> &&std::is_pointer_v<To> && + (/* No casting is necessary when both types are the same. */ + std::is_same_v<From, To> || + /* Allow adding const to the underlying type. */ + std::is_same_v<const std::remove_pointer_t<From>, std::remove_pointer_t<To>> || + /* Allow casting non-const pointers to void pointers. */ + (!std::is_const_v<std::remove_pointer_t<From>> && std::is_same_v<To, void *>) || + /* Allow casting any pointer to const void pointers. */ + std::is_same_v<To, const void *>); + +/** * Inline buffers for small-object-optimization should be disable by default. Otherwise we might * get large unexpected allocations on the stack. */ |