C/C++ Source Code Visualization

Are there any programs that can visualize structure of C++ code?

One of the best known tools is doxygen, which produces nice UML diagrams in some modes.

Tool to visualise code flow (C/C++)

SourceInsight and Understand for C++ are the best tools you can get for c/c++ code analysis including flow charts.

Good code visualization / refactoring tools for C++?

There is a KDevelop plugin for code visualization:
http://liveblue.wordpress.com/2009/08/21/gsoc-wrap-up-static-code-visualization-in-kdevelop/

C++ code visualization

Why not just do it manually, it is a great learning experience when starting to work with a large code base. I usually just look at what class inherits from what, and what class contain what instances, references or pointers to other classes. Have a piece of paper next to you and get drawing...

Does a Tool for Automatically Visualizing a Project's Source Code's Control Flow In-Line Exist?

You aren't going to get a tool that does this for arbitrary languages off the shelf. There are too many languages, each with its own syntax and semantics. You somehow need a tool per language. You might find such tools for very commonly used languages, e.g, Understand for Software.

I think that the only way to do this is to build metatools that enable the construction of language-specific tools relatively easily. Such a tool has to have the common machinery needed by all such language processing tools: strong parsers (so writing grammars for languages is relatively straightforward), AST construction machinery, symbol table support, routines to build control and data flow graphs. By providing such machinery, one can build language front ends for modest costs.

There's a class of tools that does this, program transformation. Most of them have parsing engines, but not the rest of the mechanisms I have suggested above.

I believe this enough to have invested 20 years of my life to building
such meta tools. Our DMS Software Reengineering toolkit shows its strength in being able to parse some 50+ languages, including the stunningly hard C++14 (both MS and GNU variants). It shows symbol table support and control flow graph construction for COBOL, Java, C, C++. (We can't do everything at once; pedaling as fast as practical).
[DMS builds these graphs as data structures rather than "showing" them; the examples on that page are drawn with the additional help of DOT].

One of the few other tools that tries to do this is Clang/LLVM; this covers a wide variety of popular languages. Clang doesn't have any specific support for parsing that I know about; you get to code it all yourself. I think you get control flow graphs only after you convert the language to LLVM. I don't think it has any specific support for drawing control flow graphs, either.

An older tool with a good reputation for multi-language support in this space is CoCo/R;
I don't know a lot about it. I know it parses,
and has some support for ASTs; I don't know what it does
about control flow analysis.