Comment by Conscat
18 hours ago
Clang supports C11 - 23 in C++, as well as some future C features like fixed-point integers. The main pain points with Clang are just the fundamental differences like void* and char, which don't typically matter much at an interoperability layer.
There's a lot of subtle differences between 'proper' C and the C subset of C++, since C++ uses C++ semantics everywhere, even for its C subset.
Many C++ coders are oblivious to those differences (myself included before I switched from 'mainly C++' to 'mainly C') because they think that the C subset of C++ is compatible with 'proper' C, but any C code that compiles both in a C++ and C compiler is actually also a (heavily outdated) subset of the C language (so for a C coder it takes extra effort to write C++ compatible C code, and it's not great because it's a throwback to the mid-90s, C++ compatible C is potentially less safe and harder to maintain).
For instance in C++ it's illegal to take the address of an 'adhoc-constructed' function argument, like:
(godbolt: https://www.godbolt.org/z/r7r5rPc6K)
Interestingly, Objective-C leaves its C subset alone, so it is always automatically compatible with the latest C features without requiring a new 'ObjC standard'.
Because Objective-C initial proposal is that everything that isn't touched by Smalltalk like code, clearly in brackets or @annotarions, is plain C.
The pre-processor original compiler, before the GCC fork, would leave everything else alone, blindly copying into the generated C file.