Fix examples web smoke: ServeCompileCache constant mutation (#12040)

lib/Block.php

@@ -466,6 +466,20 @@ public function registerConstant(Operand $operand, Variable $const): int {
         return $slot;
     }
 
+    /**
+     * Per-run copy of a compile-time constant for frame scope (#12040, ServeCompileCache).
+     *
+     * Cached {@see Block} instances must not share {@see Variable} cells with execution
+     * scope — builtins may coerce/mutate argument operands in place.
+     */
+    private function scopeConstantVariable(int $slot): Variable
+    {
+        $copy = new Variable();
+        $copy->duplicateFrom($this->constants[$slot]);
+
+        return $copy;
+    }
+
     /**
      * Copy cfg Var root slot mappings from a sibling branch (?: / if merge, #3790).
      */
@@ -875,7 +889,7 @@ public function getFrame(Context $context, ?Frame $frame = null): Frame {
             // Variable reads in args must still resolve (#3787 merge + literal arm).
             if (isset($scope[$pos]) && !$this->args->contains($op)) {
                 if (isset($this->constants[$pos])) {
-                    $scope[$pos] = $this->constants[$pos];
+                    $scope[$pos] = $this->scopeConstantVariable($pos);
                 }
 
                 continue;
@@ -908,7 +922,7 @@ public function getFrame(Context $context, ?Frame $frame = null): Frame {
             }
 
             if (isset($this->constants[$pos]) && !$this->args->contains($op)) {
-                $scope[$pos] = $this->constants[$pos];
+                $scope[$pos] = $this->scopeConstantVariable($pos);
             } elseif (isset($this->closureCaptureSlots[$pos])) {
                 $scope[$pos] = self::initialVariableForOperand($op, $context, $pos, $this);
             } elseif ($this->isArgRecvParameterSlot($pos)) {
@@ -1055,13 +1069,13 @@ private function ensureOpcodeReferencedSlots(array &$scope): void
         for ($i = 0; $i <= $max; ++$i) {
             if (isset($scope[$i])) {
                 if (isset($this->constants[$i])) {
-                    $scope[$i] = $this->constants[$i];
+                    $scope[$i] = $this->scopeConstantVariable($i);
                 }
 
                 continue;
             }
             if (isset($this->constants[$i])) {
-                $scope[$i] = $this->constants[$i];
+                $scope[$i] = $this->scopeConstantVariable($i);
 
                 continue;
             }

lib/Web/DevServer.php

@@ -680,6 +680,9 @@ public static function respond($conn, int $status, string $contentType, string $
         $out .= "Content-Type: {$contentType}\r\n";
         $out .= 'Content-Length: '.strlen($body)."\r\n";
         foreach ($extraHeaders as $line) {
+            if ('' === $line) {
+                continue;
+            }
             if (stripos($line, 'Content-Type:') === 0) {
                 continue;
             }

lib/Web/ResponseContext.php

@@ -122,6 +122,9 @@ public static function assertSafeHeaderLine(string $line): void
 
     public static function addHeader(string $line, bool $replace = true): void
     {
+        if ('' === $line) {
+            return;
+        }
         self::assertSafeHeaderLine($line);
         if (preg_match('#^HTTP/\d(?:\.\d)?\s+(\d{3})#', $line, $m)) {
             self::setStatus((int) $m[1]);

test/unit/Web/ServeCompileCacheConstantsTest.php

@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PHPCompiler;
+
+use PHPCompiler\VM\OutputBuffer;
+use PHPCompiler\VM\ShutdownQueue;
+use PHPCompiler\ext\standard\VmSession;
+use PHPCompiler\ext\standard\VmStatCache;
+use PHPCompiler\Web\DevServer;
+use PHPCompiler\Web\ProjectBootstrap;
+use PHPCompiler\Web\ResponseContext;
+use PHPCompiler\Web\ServeCompileCache;
+use PHPCompiler\Web\Superglobals;
+use PHPUnit\Framework\TestCase;
+
+/** ServeCompileCache must not share mutable constant cells across VM runs (#12040). */
+final class ServeCompileCacheConstantsTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        ServeCompileCache::reset();
+        parent::tearDown();
+    }
+
+    public function testCachedEntryScriptKeepsHeaderLiteralAcrossRuns(): void
+    {
+        $script = realpath(__DIR__.'/../../../examples/002-StaticWeb/example.php');
+        $this->assertNotFalse($script);
+        $docroot = dirname($script);
+
+        ServeCompileCache::enable();
+        $runtime = new Runtime();
+        [$projectDir, $manifest] = ProjectBootstrap::resolveFromScript($script);
+        ProjectBootstrap::prepare($runtime, $projectDir, $manifest);
+        $block = ServeCompileCache::getFile($runtime, $script);
+        $this->assertNotNull($block);
+
+        foreach (['/example.php', '/example.php'] as $requestUri) {
+            ResponseContext::reset();
+            ResponseContext::enableHeaderQueue();
+            VmSession::reset();
+            VmStatCache::reset();
+            OutputBuffer::reset();
+            ShutdownQueue::reset();
+            DevServer::clearHttpServerKeys();
+
+            putenv('REQUEST_METHOD=GET');
+            putenv('QUERY_STRING=');
+            putenv('REQUEST_BODY=');
+            putenv('SCRIPT_NAME=/example.php');
+            putenv('SCRIPT_FILENAME='.$script);
+            putenv('REQUEST_URI='.$requestUri);
+            putenv('DOCUMENT_ROOT='.$docroot);
+            putenv('SERVER_PROTOCOL=HTTP/1.1');
+            putenv('PATH_INFO');
+            Superglobals::applyHttpHeaders(['host' => 'localhost', 'connection' => 'close']);
+
+            $run = new Runtime();
+            Superglobals::populateFromEnvironment($run->vmContext, '', '', $script);
+            ProjectBootstrap::prepare($run, $projectDir, $manifest);
+            $cached = ServeCompileCache::getFile($run, $script);
+            $this->assertSame($block, $cached);
+            $run->run($cached);
+
+            $this->assertSame(
+                ['Content-Type: text/html; charset=UTF-8'],
+                ResponseContext::listHeaders(),
+                'request '.$requestUri
+            );
+        }
+    }
+}