| Thanks for your reply! First off, I work mainly in C++ (Windows, Linux, macOS and some embedded) and I don't hate the language. I really wished that C++ had a well-specified ABI, but the sad reality is that it doesn't. > if the code generated by a compiler targeting a given platform, does not match the ABI used by that platform, the problem is the compiler is generating broken code. The compiler only has to correctly implement the C++ standard. The standard does not specify things like calling conventions, struct padding, implementation of virtual functions, so the compiler is free to do anything it wants. (Whether that is a good idea is another topic.) > No, vtables are implemented incorrectly by the compiler. The C++ standard does not even mandate that virtual functions are implemented with vtables. > The ABI for vtables is specified for every non-trivial platform. The ABI for argument parameter ordering is specified for every platform. The ABI for struct layout and struct padding is specified for every platform. AFAIK, Microsoft does not officially specify a C++ ABI at all (correct me if I'm wrong!) The only thing that comes close is COM - which can be implemented with a restricted subset of C++, but is really language-agnostic. > Importantly, claiming that it's a sign that C++ doesn't have an ABI, or that ABI isn't stable, is simply incorrect. The fact that it exists as a name we can reference is an indication that the ABI matters enough that it is specified. 'thiscall' is not part of the C++ standard, it is a calling convention invented by Microsoft. The C++ standard does not talk about calling conventions at all. > Mercifully in the consumer 64-bit every compiler seems to have essentially gravitated to the itanium ABI This is true on Linux, but Microsoft specifies its own 64-bit calling convention (https://docs.microsoft.com/en-us/cpp/build/x64-calling-conve...) and leaves other parts of the C++ ABI unspecified. Generally, you are right that some platforms, like Linux, have a de-facto C++ ABI, but that is not the same as saying that C++ itself has a well-defined ABI - which is simply not true. Your initial claim was that binaries compiled with different compilers are always compatible (apart from possible library ABI mismatches). We both may wish this were true, but it is false in the general case (and specifically on Windows). |