Regression: clamp() callable on ≤8.5 profiles — PHP 8.6-only API leaks (ext/standard/math.c, re-gate CompilerVersion)

[PurHur]

Category

stdlib · php-src-strict · profile gate / phantom API

Problem

clamp() landed in php-src 8.6 (RFC clamp_v2, PR #19434). This repo already implements it (ext/standard/clamp.php, VmMath::clamp, JitClamp) but gates are wrong vs Zend:

• Comments / supportsClamp() treat it as PHP 8.3+
• Under PHP_COMPILER_PROFILE=8.4: function_exists('clamp') is false, yet clamp(5,1,3) returns 3 (callable via supportsClamp while advertisesClamp hides it)
• Under PROFILE=8.3: function_exists is true and call works — Zend 8.3 has no clamp
• Under PROFILE=8.6: still not advertised/aligned with Zend 8.6

Verified 2026-07-19 on master (VERSION=8.4.0-dev):

Profile	function_exists('clamp')	clamp(5,1,3)	Zend
8.3	true	3	undefined function
8.4	false	3 (still callable!)	undefined function
8.6	false	(callable if supports)	3 + exists true

php-src reference

• php/php-src ext/standard/math.c — PHP_FUNCTION(clamp) / php_math_clamp
• php/php-src ext/standard/basic_functions.stub.php — clamp (master / 8.6)
• RFC: https://wiki.php.net/rfc/clamp_v2 (Implemented in PHP 8.6)

PHP implementation target

• Retarget CompilerVersion::supportsClamp() / advertisesClamp() to language profile ≥ 8.6 (both register and function_exists)
• Keep PHP implementation; fix docs that say “PHP 8.3”
• On ≤8.5 profiles: undefined-function Error like Zend (no silent call path)
• No new C

Repro

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
cat > /tmp/clamp_gate.php << "PHP"
<?php
echo "exists=", function_exists("clamp") ? "1" : "0", "\n";
try {
  echo "call=", clamp(5, 1, 3), "\n";
} catch (Throwable $e) {
  echo get_class($e), ": ", $e->getMessage(), "\n";
}
PHP
for p in 8.3 8.4 8.6; do
  echo "=== PROFILE=$p ==="
  PHP_COMPILER_PROFILE=$p php bin/vm.php /tmp/clamp_gate.php
done'

Done when

• PROFILE≤8.5: function_exists false and call throws undefined-function Error (php-src-strict)
• PROFILE=8.6 (or ≥8.6): function_exists true; clamp(5,1,3)===3; ValueError on min>max / NAN bounds like Zend
• Compliance .phpt for both phantom and forward profiles; php-src-strict

Related

• Stdlib: PHP 8.4 forward-profile builtin registration batch — json_validate, mb_trim, get_object_id, array_find (ext/*, lib/CompilerVersion.php) #17677 (forward-profile registration batch) · Strategic alignment: compiler excellence pillars (2026 H2) #10533 pillar 4

[PurHur]

claim: PHP Compiler STD Lib Advanced — batch (issues #21020, #21021, #21022)

Queued after stream 8.6 APIs. Retarget clamp support/advertise to profile ≥ 8.6.

[PurHur]

Merged via PR — clamp gated to PROFILE≥8.6; phantom on ≤8.5; phpunit stdlib/clamp OK.