[WIP] Create CodeQL tracing playground sample project

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Create a new GitHub repository called codeql-tracing-playground with a sample C++ project designed to test and explore CodeQL's build tracing behavior. The project should be buildable with a simple make command and include several files and scenarios that exercise different aspects of how tracing works.

Project Structure

Create the following structure:

codeql-tracing-playground/
├── README.md
├── Makefile
├── src/
│   ├── main.cpp
│   ├── utils.cpp
│   ├── utils.h
│   ├── math_ops.cpp
│   ├── math_ops.h
│   └── generated/        # For dynamically generated code
├── scripts/
│   └── generate_config.sh  # Script that generates a header file during build
└── . gitignore

Requirements

1. Multiple compilation units: The project should have at least 3-4 . cpp files that get compiled separately and linked together, so we can see multiple compiler invocations being traced.

2. Generated code during build: Include a shell script (scripts/generate_config.sh) that the Makefile calls during the build to generate a header file (src/generated/config.h) containing build timestamp or version info. This tests whether tracing correctly handles code that doesn't exist until build time.

3. Conditional compilation: Use some #ifdef preprocessor directives that are controlled by -D flags passed in the Makefile (e.g., DEBUG_MODE). This helps verify that the tracer captures the actual flags used.

4. Simple function calls across files: Have main.cpp call functions from both utils.cpp and math_ops.cpp so we can see cross-file references in the resulting database.

5. A recursive function: Include at least one recursive function (perhaps a factorial or fibonacci in math_ops.cpp) - useful for later testing dataflow analysis.

6. Makefile features:

• Separate compilation and linking steps (not just one big compile command)
• A clean target
• A DEBUG=1 option that adds -g and -DDEBUG_MODE flags
• Phony targets for the generated code step

7. README. md: Include instructions for:

• Building normally (make)
• Building with debug flags (make DEBUG=1)
• Cleaning (make clean)
• A section on how to create a CodeQL database from this project

Code Content Ideas

• utils.cpp: String manipulation helpers, maybe a simple logging function that behaves differently based on DEBUG_MODE
• math_ops.cpp: Basic math operations including the recursive function, perhaps some pointer arithmetic to make things interesting for analysis
• main.cpp: Ties everything together, reads the generated config, calls functions from other modules

. gitignore

Should ignore:

• Built objects (*.o, the final binary)
• The generated header file (src/generated/config.h)
• Any CodeQL database directories (*-db/, *. dbscheme)

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