build(prof): Fix bindgen compatibility with PHP 8.5.1+ on macOS

[realFlowControl]

Description

When compiling the profiler on macOS with Homebrew Clang >= 19, bindgen fails with:

  thread 'main' panicked at bindgen-0.69.5/ir/function.rs:263:34:                                                                                                                                                   
  Cannot turn unknown calling convention to tokens: 20     

PHP 8.5.0 introduced the TAILCALL VM, a performance optimization that uses __attribute__((preserve_none)) for opcode handler function pointers. This is enabled when compiling PHP with a compiler that supports the preserve_none attribute (Clang >= 19) on x86_64 or aarch64.

The problem is that bindgen does not support CXCallingConv_PreserveNone (calling convention 20) and panics when parsing PHP headers containing these typedefs (zend_vm_opcode_handler_t, zend_vm_opcode_handler_func_t in our case).

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[datadog-datadog-prod-us1]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

❄️ 1 New flaky test detected

ext/standard/tests/network/fsockopen_variation2.phpt (testing fsockopen() with udp sockets) from php.ext.standard.tests.network (Datadog) (Fix with Cursor)

--
     resource(%d) of type (stream)
     
     Pass some data between the sockets:
007- string(10) "0123456789"
007+ bool(false)
     
     Calling fsockopen() with address and port in same string:
     resource(%d) of type (stream)
--

🧪 1024 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: 696e4bb40000000048996296e2ccfb6d
tid: 696e4bb400000000
hexProcessTraceId: 48996296e2ccfb6d
hexProcessSpanId: 3561a9b9cd86d800
processTraceId: 5231320842357242733
processSpanId: 3846542172233324544

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

View all

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[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-01-19 15:13:03

Comparing candidate commit 0696d7d in PR branch florian/fix-macos-bindgen with baseline commit 434d817 in branch master.

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