Re: "C++ has its place , but this sort of low level almost to-the-metal code is not it."
From your heartfelt complaints, I infer that you were once exposed to some complete idiots who took the C++ language spec as a challenge, and you've developed a hyper-sensitivity to feature abuse as a result.
For code like this, I'd reckon that idiomatic C++ would differ from idiomatic C only in using constructors and destructors to automate memory management and structure initialisation/cleanup. There might be a large-integer class with overloaded arithmetic operators, but if you can't handle using infix operator notation for integer arithmetic then you probably can't handle the theory behind SSL.
I'd expect an almost line-for-line correspondence between the two code bases. I'd expect the two compilers to generate almost identical code. I'd expect an experienced C coder with only a passing knowledge of C++ to be able to read and maintain the C++ safely.
C++ was largely developed by experienced C coders who wanted to make it easier for themselves to write C code, and one of the basic design principles is "no room for a lower level language, except assembler", so all the bare-metal tricks beloved by C coders are valid C++. A Real Programmer, of course, can write FORTRAN 66 in either language.