I am using CodeQL to analyze a very large, private C project and have encountered a couple of issues. I would be grateful for any help or guidance you can provide.

Problem 1: Out-of-Memory (OOM) During Database Creation

When I attempt to create a CodeQL database from the project's root directory, the process fails with an Out-of-Memory (OOM) error. This error occurs before the actual compilation phase begins.

Observations:

• The project is extremely large.
• The machine has over 40GB of free RAM at the time of the OOM error.
• As a workaround, I can successfully create a database without an OOM error if I set the --source-root to a smaller, specific subdirectory that I am interested in.

Questions:

1. What pre-build operations does the CodeQL CLI perform that could consume so much memory, even when significant physical RAM is available?
2. What is the recommended best practice or workflow for creating a database for a very large C project to avoid these OOM issues?

Problem 2: Incomplete Tracing for Most Compiled Files

I've noticed that most C files are not being fully analyzed, even though they are part of the compilation.

Observations:

• A specific file, let's call it example.c, is definitely being compiled.
• I have inspected the build-tracer.log and can confirm that the CodeQL tracer has captured its compilation process. The log contains the complete invocation, Command, and Processed command line for example.c.
• This issue affects the majority of the files in the project. For these files, it seems that none of their internal contents (functions, expressions, variables, etc.) have been extracted.
• When I query the database, the only result related to example.c is its file-level location (example.c:0:0:0:0). A small number of other files are partially traced, where I can identify some expressions (expr), but the analysis is still far from complete.

For example, running the following query on the database highlights this issue:

from Locatable locb, Location loc
where locb.getLocation() = loc
select locb, loc

The query shows that for files like example.c, only the file itself is located, with no deeper elements available.

Question:

• Why might the contents of most files not be extracted into the database, even though their build commands were successfully captured by the build tracer?