Show HN: Clang-uml – C++ to UML diagram generator based on Clang

The only reason UML didn't pan out was because it isn't code, and if it's not code, software engineers don't want to do it because software engineers are lazy when it comes to things that are neither code nor one-step-away-from-code tasks. They will go build a million different things instead of documenting. As a consequence, they lose their engineering title and get called developers.

UML works.

One can lead a horse to water... just like one can stand up ALL of the top, fully-functional UML tools for a software team at what used to be a performant defense contractor, and have literally ZERO people use it.

Same with system engineers and commitment. Requirements work. Model driven time wasting doesn't.

> Remember the days people thought they could build everything in UML diagrams, and have the code essentially be generated or trivially written from there?

Those days were a decade ago, and everyone with a license to software like Enterprise Architect did that already with a click of a button.

Even before that this was at the reach of everyone with FLOSS tools like Umbrella.

What exactly was your point?

> Fast forward to 2023 and we're generating UML diagrams from C++ code because it's easier. I love this.

You missed the whole point of this tool. This tool is ideal for those of us who work on legacy projects and want a high level view of the project structure to make it easier to get a feel of the project.

I'd bet with GPT-XX based code generation this might UML sequence diagrams may make a resurgence. its at least good to run some kind of automated 'design lint' to run even if just to ensure a new feature or commit has not broken the high level assumptions/state machine. The codebase I work in I definitely could use something like this regularly.

UML... the only pictures that _don't_ paint a thousand words!

Not sure what cursed C++ you've seen but UML is easily 100x worse.

There may be a few hundred good C++ programmers around but nobody can grok UML, if somebody says they can: they're a liar.

This is why code bases from the Java 1.4 days are so unwieldy.

Yes, absolutely, in fact clang-uml also uses Doxygen for it's own documentation - although diagrams are 'self'-generated by clang-uml - for instance see here: https://clang-uml.github.io/structclanguml_1_1config_1_1conf...

However, the main difference between clang-uml and Doxygen is that in Doxygen the diagrams are a by-product of generated documentation. clang-uml aims to give you much more control over what you want in your diagrams, without having to use Doxygen or any other documentation tool, which possibly makes it more flexible in how you can use its output.

Obviously, which approach you prefer depends on your use case and needs.

F# and OCaml are kind of great for this in my opinion.

With F# in particular, the code project/workspace has a root .fsproj file where you list the dependency order of files. The topmost file cannot depend/call anything from any of the files below, and the bottom most file is the program's entry point depending on all the other files in the project and which itself cannot be depended on. OCaml has the same rule, but the dependency order is automatically detected (which I comparatively dislike to be honest as the .fsproj file serves as easy documentation - although I've seen tools that generate a graph for OCaml's dependency order).

The same dependency rule (code at the top of the file cannot call code below) is followed within a single file too by default. It is possible to opt-out of this rule in an intra-file (within the same file basis) but discouraged to do so I think.

I've found that much more helpful in understanding code than UML diagrams in all honesty.

I remember (before I learned F# or OCaml) reading some of VS Code's source code[0] for learning purposes and finding that class A referenced another class B, and that class B referenced class A which I found confusing. I managed to overcome my issue by drawing a dependency tree of functions which gave some chronological order and understanding.

[0] This to be precise: https://github.com/microsoft/vscode-textbuffer .

>Most confusion for me happens around dynamic dispatch. I want a good tool to generate and control dynamic call graphs.

I use the profiler (eg. gprof call graph) and good old "printf/log tracing" for this.

PS: See also -finstrument-functions in gcc : https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.h... and https://balau82.wordpress.com/2010/10/06/trace-and-profile-f...

I used Umbrello (https://apps.kde.org/umbrello/) in the long long ago, might be worth checking out too if you haven't already.