Stdlib: fpow()/fmin()/fmax()/nextafter() — callable on PHP_COMPILER_PROFILE=8.4 but function_exists false (BuiltinIntrospectionPolicy, ext/standard/math.c)

[PurHur]

Category

stdlib · php-src-strict · introspection parity

Problem

On PHP_COMPILER_PROFILE=8.4, IEEE math builtins are registered for direct calls but withheld from function_exists() until CompilerVersion::VERSION reaches stable 8.4.0. Zend 8.4 advertises these functions when the language profile supports them; code using function_exists('fpow') before calling breaks.

Call / probe	Zend 8.4+ (forward)	VM PHP_COMPILER_PROFILE=8.4 (2026-07-05)
fpow(2, 3)	8	8 (callable)
function_exists('fpow')	true	false
function_exists('nextafter')	true	false

Same pattern for fmin() / fmax().

php-src reference

• php/php-src ext/standard/math.c — zend_fpow, zend_nextafter
• php/php-src ext/standard/basic_functions.c — function_exists registration

PHP implementation target

• ext/standard/BuiltinIntrospectionPolicy.php — advertise when supportsFpow() / supportsNextafter() true on forward profile, not only advertisesFpow() stable runtime
• lib/CompilerVersion.php — align advertisesFpow() / advertisesNextafter() with languageProfileVersion() (mirror Stdlib: PHP 8.4 forward-profile gated builtins — function_exists/extension_loaded true on reference profile (ext/standard) #16086 bcmath pattern decision)
• ext/standard/Module.php — registration already present; introspection-only fix

Repro

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && PHP_COMPILER_PROFILE=8.4 php bin/vm.php test/repro/maintainer_gap_fpow_function_exists_forward_84.php'
PHP_COMPILER_PROFILE=8.4 php bin/vm.php test/repro/maintainer_gap_fpow_function_exists_forward_84.php

Done when

• Repro prints ok: fpow advertised (and siblings) on forward profile
• Reference profile (no env) still reports function_exists('fpow') === false like Zend 8.2
• Compliance guard under test/compliance/cases/stdlib/
• php-src-strict; no php-compiler-strict shortcut

Related

• Closed php-in-php: fpow() early registration — align #4605 with VmMath, version gate, and IEEE edge cases #7045, Stdlib: PHP 8.4 forward-profile gated builtins — function_exists/extension_loaded true on reference profile (ext/standard) #16086 — fpow registration / introspection split
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 north star

[PurHur]

Cleanup bot — canonical tracking

This is the remaining fpow/fmin/fmax/nextafter introspection slice after closed umbrella #16086 (forward-profile phantom function_exists batch). Do not re-file as a duplicate of #16086; implement here against BuiltinIntrospectionPolicy + compliance skip in #16661.

Related open cluster: #16677 (this issue) only — not #16086 (closed).

[PurHur]

claim: cursor-agent-lane-a — starting this run

[PurHur]

Merged via #16683

Fix: advertisesFpow() / advertisesNextafter() now follow languageProfileVersion() (same pattern as advertisesHttpLastResponseHeaders()), so function_exists('fpow'|'fmin'|'fmax'|'nextafter') is true under PHP_COMPILER_PROFILE=8.4 while the 8.2 reference harness still reports false.

Verification:

PHP_COMPILER_PROFILE=8.4 php bin/vm.php test/repro/maintainer_gap_fpow_function_exists_forward_84.php
# ok: fpow advertised

php bin/vm.php test/repro/maintainer_gap_fpow_phantom_registration.php
# ok

vendor/bin/phpunit --filter fpow_function_exists_forward_profile test/compliance/VMTest.php
# OK