fix(prof): PHP 8.4 crash with opcache optimizer

[morrisonlevi]

Description

The profiler may crash when:

1. The profiler is enabled,
2. Allocation profiling is enabled (on by default),
3. The application is on PHP 8.4,
4. and Opcache is enabled and used (strongly recommended for production).

If allocation profiling triggers at a precise spot in the optimizer, then it will dereference a null pointer. The reason is that the optimizer puts a fake frame with a zeroed opline in accel_preload, and the profiler does not check for null at this location.

There are other access in the profiler to the opline such as extract_file_and_line, but they already guard against a null pointer. This specific bit of code that did not guard was added for PHP 8.4 to handle frameless functions, a new optimization in PHP 8.4.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.80%. Comparing base (46ec759) to head (38c0dda).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #3038   +/-   ##
=========================================
  Coverage     74.80%   74.80%           
  Complexity     2781     2781           
=========================================
  Files           112      112           
  Lines         11017    11017           
=========================================
  Hits           8241     8241           
  Misses         2776     2776           

Flag	Coverage Δ
tracer-php	74.80% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 46ec759...38c0dda. Read the comment docs.

[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2025-01-14 21:46:05

Comparing candidate commit 38c0dda in PR branch levi/fix-8.4-opline with baseline commit 46ec759 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 29 metrics, 7 unstable metrics.