Regression: fadd/fsub/fmul/fmax/fmin/nextafter phantoms on PROFILE≥8.4 — absent from php-src (ext/standard/math.c) #28565

Category

bug · php-src-strict · PROFILE≥8.4 phantom builtins · pillar 4

Problem

Under PHP_COMPILER_PROFILE=8.4 / 8.5, function_exists() is true for fadd, fsub, fmul, fmax, fmin, and nextafter, and positional calls succeed. Zend/php-src 8.4.24 and 8.5.8 do not define these functions (function_exists false). They are compiler phantoms — not Reflection-stub mismatches against real Zend APIs.

Sibling #27617 assumed Zend float stubs exist; live php:8.4-cli / php:8.5-cli show otherwise. fpow / fdiv / fmod do exist on Zend and are out of scope here.

Probed 2026-08-07 @ fdf529e8bd.

php-src reference

• php/php-src ext/standard/math.c — fpow/fdiv/fmod only among this family
• No fadd/fmax/nextafter in php-src 8.4/8.5 stubs (verified via live Zend containers)

PHP implementation target

• Gate or remove fadd/fsub/fmul/fmax/fmin/nextafter advertisement + implementations unless/until php-src lands them
• Fix function_exists / BuiltinIntrospectionPolicy / ext/standard registrations for PROFILE≥8.4
• Supersedes the Zend-stub premise of Regression: fadd/fsub/fmul/fmax/fmin/nextafter Reflection arity 0 — Zend float stubs (ext/standard/math.stub.php) #27617 — close or retarget that issue when this lands
• PHP-in-PHP; no new C

Repro

./script/docker-exec.sh -- bash -lc 'cat > /tmp/fmath.php <<'"'"'PHP'"'"'
<?php
foreach (["fadd","fsub","fmul","fmax","fmin","nextafter","fpow"] as $f) {
  echo $f, "=", function_exists($f) ? "Y" : "N", "\n";
}
PHP
echo VM84:; PHP_COMPILER_PROFILE=8.4 php bin/vm.php /tmp/fmath.php'
# Zend: docker run --rm -i php:8.4-cli php < /tmp/fmath.php

Expected (Zend): only fpow=Y among the phantom set; fadd…nextafter=N.

Done when

• PROFILE 8.4/8.5: function_exists false for the six phantoms (matching Zend)
• Positional calls fatal as undefined (or gated identically to Zend)
• Compliance guard; php-src-strict
• Regression: fadd/fsub/fmul/fmax/fmin/nextafter Reflection arity 0 — Zend float stubs (ext/standard/math.stub.php) #27617 closed or rewritten against this done-when