fix(prof): allocation profiling for PHP 8.4

[realFlowControl]

Description

Since #3360 and with #3361 we disabled the code path for PHP 8.4's php_zend_mm_set_custom_handlers_ex(). This PR re-enables that code path again.

This uses the same approach as PHP <= 8.3 allocation profiling with the difference that for alloc(), realloc() and free() calls we do not "prepare" the ZendMM heap by manipulating the heap->use_custom_heap flag anymore. This was necessary for when the allocation fails, ZendMM might call zend_mm_gc() to try and free memory for a new chunk which would just return 0; in case a custom allocator is installed.

With us being able to hook into zend_mm_gc() we can stop manipulating the heap->use_custom_heap flag in the allocator hot path and only do so in case a zend_mm_gc() was triggered.

Additionally this adds a prof correctness tests with another custom allocator being used by setting USE_ZEND_ALLOC=0.

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 61.81%. Comparing base (7ce9fd6) to head (4cee785).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3550   +/-   ##
=======================================
  Coverage   61.81%   61.81%           
=======================================
  Files         140      140           
  Lines       13281    13281           
  Branches     1758     1758           
=======================================
  Hits         8209     8209           
  Misses       4282     4282           
  Partials      790      790           

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[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-01-13 14:24:58

Comparing candidate commit 4cee785 in PR branch florian/alloc-php-84 with baseline commit 7ce9fd6 in branch master.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 28 metrics, 7 unstable metrics.

scenario:php-profiler-timeline-memory-with-profiler

• 🟩 cpu_user_time [-45.081ms; -27.034ms] or [-3.889%; -2.332%]

[datadog-official]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 1022 Tests failed

    testSearchPhpBinaries from integration.DDTrace\Tests\Integration\PHPInstallerTest (Fix with Cursor)

    testSimplePushAndProcess from laravel-58-test.DDTrace\Tests\Integrations\Laravel\V5_8\QueueTest (Fix with Cursor)

testSimplePushAndProcess from laravel-8x-test.DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest::testSimplePushAndProcess
Test code or tested code printed unexpected output: spanLinksTraceId: 696664720000000039e85f4f6c02b605
tid: 6966647200000000
hexProcessTraceId: 39e85f4f6c02b605
hexProcessSpanId: 062a6117efc4fb87
processTraceId: 4172689849477936645
processSpanId: 444274268684221319

phpvfscomposer://tests/vendor/phpunit/phpunit/phpunit:106

View all

ℹ️ Info

❄️ No new flaky tests detected

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