src: map UINT64_MAX to 0 in process.constrainedMemory()

[crawfordxx]

Summary

When uv_get_constrained_memory() returns UINT64_MAX, it indicates there is a constraining mechanism (e.g., cgroups on Linux) but no constraint is actually set. According to the Node.js documentation, this case should return 0:

If there is no constraint, or the constraint is unknown, 0 is returned.

Currently, the raw UINT64_MAX value (18446744073709552000 as a double) is exposed to JavaScript, which contradicts the documented behavior.

Changes

• In GetConstrainedMemory(), check if uv_get_constrained_memory() returns UINT64_MAX and map it to 0
• Added <cstdint> include to ensure UINT64_MAX is defined

References

• libuv docs: https://docs.libuv.org/en/v1.x/misc.html#c.uv_get_constrained_memory
• Node.js docs: https://nodejs.org/api/process.html#processconstrainedmemory

Fixes: #59227

[anonrig]

Can you add a comment explaining this? Can this be tested?

[crawfordxx]

Good point. I'll add an inline comment explaining the UINT64_MAX check.

For testing — this is tricky to unit test because uv_get_constrained_memory() depends on cgroup configuration at the OS level. On a system with cgroups enabled but no memory limit set (e.g. a default Docker container without --memory), the function returns UINT64_MAX. We could potentially add a test that mocks the libuv return value, but that would require refactoring to accept a dependency. Would a simple inline comment be sufficient, or would you prefer a test approach?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.66%. Comparing base (9ff27fd) to head (fd33a53).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62209      +/-   ##
==========================================
+ Coverage   89.63%   89.66%   +0.02%     
==========================================
  Files         676      676              
  Lines      206578   206452     -126     
  Branches    39555    39523      -32     
==========================================
- Hits       185171   185105      -66     
+ Misses      13535    13488      -47     
+ Partials     7872     7859      -13     

Files with missing lines	Coverage Δ
src/node_process_methods.cc	88.20% <100.00%> (+0.02%)	⬆️

... and 35 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.