You need a disassembler , which is a tool that takes a binary object (like a compiled file, a library, or even an executable) and tries to reinterpret its content as assembly.
With a tool like that you can usually retrieve the names of the internal symbols (unless of course the binary image is stripped, but this is not the case for dynamically liked libraries).
Also for C++ this is a bit difficult because of name mangling.
Try to give a glance to Objdump.
YOu can disassemble the code sections of the DUMPBIN /DISASS - but if you want “code” like C++, then you need a decompiler. However, they are far from great, and often make quite unreadable code - yes, it’s something that you can feed into a compiler, but it’s hardly what I’d call “human readable”.
In my biased opinion, the best disassembler out there is IDA (Interactive Disassembler). It is somewhat expensive since it’s targeted towards professional use, but there’s a freeware (older) version you can try:
The Hex-Rays Decompiler (an add-on for IDA) can produce C pseudocode from the disassembly, which can in many cases be recompiled again.
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