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| -rw-r--r-- | book/src/cpp.md | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/book/src/cpp.md b/book/src/cpp.md index 75ef8554..69285846 100644 --- a/book/src/cpp.md +++ b/book/src/cpp.md @@ -72,7 +72,10 @@ cannot translate into Rust: [the tracking issue for exceptions](https://github.com/rust-lang/rust-bindgen/issues/1208) for more details. -* Return value optimization. C++ compilers will in certain circumstances optimize functions - returning a struct type value to instead take an extra hidden argument that refers - to the return value struct. `bindgen` cannot necessarily know about this optimization and - thus at present `bindgen`-interfaces for these kinds of functions are invalid. +* Many C++ specific aspects of calling conventions. For example in the Itanium abi types that are + "[non trivial for the purposes of calls](https://itanium-cxx-abi.github.io/cxx-abi/abi.html#non-trivial)" + should be passed by pointer, even if they are otherwise eligable to be passed in a register. + Similarly in both the Itanium and MSVC ABIs such types are returned by "hidden parameter", much like + large structs in C that would not fit into a register. This also applies to types with any base classes + in the MSVC ABI (see [x64 calling convention](https://learn.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc-170#return-values)). + Because bindgen does not know about these rules generated interfaces using such types are currently invalid. |