The SIB importer, upon needing an empty aiString, did not create a new one but rather copied a predefined global empty string.
Since aiStrings contain large buffers, Assimp copied 1028 B of zeros instead of setting five bytes (at least when compiled with Visual C++). Since aiString is a user-defined type without a constexpr constructor, Visual C++ had to generate a thread-safe run-time initializer as well.
Now it’s just two instructions.
The search for a matching importer had a few issues, see #3791. There were two different mechanisms to determine whether an importer accepts a specific file extension:
1. `aiImporterDesc::mFileExtensions`, which was forwarded to the UI via `BaseImporter::GetExtensionList()`.
2. `BaseImporter::CanRead()` when called with `checkSig == false`, which determines whether to actually use that importer.
Both were redundant and got out of sync repeatedly. I removed 2. completely and replaced it with 1., thereby syncing UI/import and shortening all `BaseImporter::CanRead()` implementations.
Further bugfixes:
- fixed glTF2 importer throwing exceptions when checking whether it can load a file
- removed `BaseImporter::SimpleExtensionCheck()` because it is no longer used and had a bug with case sensitivity
Since the `checkSig` parameter in `BaseImporter::CanRead()` is now useless, it can be removed completely. I’m not sure if this would break ABI compatiblity, so I’ll submit it with a later pull request.
Aaron Gokaslan
Kim Kulling
Kim Kulling
Malcolm Tyrrell
Jason C
Krishty
Rahul Sheth