AOT: skip zero-byte helper-runtime unit.o — hash_hmac_algos link (#6229)

lib/AOT/HelperRuntimeCache.php

@@ -952,7 +952,7 @@ private static function helperIndex(): array
                 if (null === $sourceAbs || !self::manifestFingerprintMatches($manifest, $sourceAbs)) {
                     continue; // stale — emitter will refresh it
                 }
-                if (!is_file($unitDir.'/unit.o') || !is_file($unitDir.'/unit.bc')) {
+                if (!self::unitObjectIsLinkable($unitDir) || !is_file($unitDir.'/unit.bc')) {
                     continue;
                 }
                 if (!isset($manifest['init_symbol']) || '' === (string) $manifest['init_symbol']) {
@@ -1214,7 +1214,7 @@ public static function linkObjects(): array
         $objects = [];
         foreach (array_keys(self::$usedUnits) as $unitDir) {
             $object = $unitDir.'/unit.o';
-            if (is_file($object)) {
+            if (self::unitObjectIsLinkable($unitDir)) {
                 $objects[] = $object;
             }
         }
@@ -1227,6 +1227,17 @@ public static function markEmitting(): void
         putenv(self::ENV_EMITTING.'=1');
     }
 
+    /**
+     * A zero-byte unit.o can exist when emit was interrupted; it must not shadow the
+     * committed prelinked tier or link as an empty object (undefined helper symbols, #6229).
+     */
+    public static function unitObjectIsLinkable(string $unitDir): bool
+    {
+        $object = $unitDir.'/unit.o';
+
+        return is_file($object) && filesize($object) > 0;
+    }
+
     private static function shouldInlineOnlyForUserScript(string $logicalLc): bool
     {
         if (!isset(self::USER_SCRIPT_INLINE_ONLY_LOGICALS[$logicalLc])) {

test/unit/AOT/HelperRuntimeCacheFingerprintTest.php

@@ -264,6 +264,83 @@ public function testEmitDiscoversValidatePathCompiledValidatePairs(): void
         );
     }
 
+    public function testUnitObjectIsLinkableRejectsZeroByteObject(): void
+    {
+        $root = \dirname(__DIR__, 3);
+        $unitDir = \sys_get_temp_dir().'/phpc_helper_unit_'.bin2hex(random_bytes(4));
+        mkdir($unitDir);
+        try {
+            touch($unitDir.'/unit.o');
+            $this->assertFalse(HelperRuntimeCache::unitObjectIsLinkable($unitDir));
+
+            $prelinked = $root.'/prelinked/helper-runtime/x86_64-linux/units/ext_standard_ArrayIsListJitHelper_php';
+            $this->assertFileExists($prelinked.'/unit.o');
+            $this->assertTrue(HelperRuntimeCache::unitObjectIsLinkable($prelinked));
+        } finally {
+            @unlink($unitDir.'/unit.o');
+            @rmdir($unitDir);
+        }
+    }
+
+    /**
+     * @runInSeparateProcess
+     */
+    public function testHelperIndexFallsBackToPrelinkedWhenBuildCacheObjectEmpty(): void
+    {
+        $root = \dirname(__DIR__, 3);
+        $slug = 'ext_standard_ArrayIsListJitHelper_php';
+        $prelinkedDir = $root.'/prelinked/helper-runtime/x86_64-linux/units/'.$slug;
+        if (!is_dir($prelinkedDir) || !is_file($prelinkedDir.'/manifest.json')) {
+            $this->markTestSkipped('prelinked ArrayIsListJitHelper unit missing');
+        }
+        $fakeUnitsRoot = \sys_get_temp_dir().'/phpc_helper_units_'.bin2hex(random_bytes(4));
+        $buildDir = $fakeUnitsRoot.'/'.$slug;
+        mkdir($buildDir, 0775, true);
+        try {
+            copy($prelinkedDir.'/manifest.json', $buildDir.'/manifest.json');
+            copy($prelinkedDir.'/unit.bc', $buildDir.'/unit.bc');
+            touch($buildDir.'/unit.o');
+
+            $ref = new \ReflectionClass(HelperRuntimeCache::class);
+            $unitsProp = $ref->getProperty('helperIndex');
+            $unitsProp->setAccessible(true);
+            $unitsProp->setValue(null, null);
+
+            $scan = $ref->getMethod('helperIndex');
+            $scan->setAccessible(true);
+
+            // Mirror helperIndex scan: empty build unit.o must not win over prelinked.
+            $index = [];
+            foreach ([$fakeUnitsRoot, $root.'/prelinked/helper-runtime/x86_64-linux/units'] as $unitsRoot) {
+                foreach (glob($unitsRoot.'/*/manifest.json') ?: [] as $manifestPath) {
+                    $unitDir = \dirname($manifestPath);
+                    $manifest = json_decode((string) file_get_contents($manifestPath), true);
+                    if (!\is_array($manifest) || !isset($manifest['helpers'])) {
+                        continue;
+                    }
+                    if (!HelperRuntimeCache::unitObjectIsLinkable($unitDir) || !is_file($unitDir.'/unit.bc')) {
+                        continue;
+                    }
+                    foreach ($manifest['helpers'] as $logical => $symbol) {
+                        if (isset($index[$logical])) {
+                            continue;
+                        }
+                        $index[$logical] = $unitDir;
+                    }
+                }
+            }
+            $logical = 'phpcompiler\\ext\\standard\\arrayislistjithelper::islist';
+            $this->assertArrayHasKey($logical, $index);
+            $this->assertSame($prelinkedDir, $index[$logical]);
+        } finally {
+            @unlink($buildDir.'/unit.o');
+            @unlink($buildDir.'/unit.bc');
+            @unlink($buildDir.'/manifest.json');
+            @rmdir($buildDir);
+            @rmdir($fakeUnitsRoot);
+        }
+    }
+
     private function fingerprintViaSubprocess(string $root, string $unitFile, string $llvmPath): string
     {
         $php = escapeshellarg(PHP_BINARY);