From 2af1d36bc59ec882e20c67788df4c38a0fd37b37 Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Wed, 8 Jul 2020 10:10:32 +0200
Subject: [PATCH] Skip special function optimization for redeclared disabled
 functions

As pointed out on GH-5817.
---
 Zend/tests/bug79382.phpt | 6 ++----
 Zend/zend_compile.c      | 6 ++++++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Zend/tests/bug79382.phpt b/Zend/tests/bug79382.phpt
index bc6099c4e4..5c1abe2d5f 100644
--- a/Zend/tests/bug79382.phpt
+++ b/Zend/tests/bug79382.phpt
@@ -6,13 +6,11 @@ disable_functions=strlen
 <?php
 
 function strlen(string $x): int {
-    $len = 0;
-    while (isset($x[$len])) $len++;
-    return $len;
+    return 42;
 }
 
 var_dump(strlen("foobar"));
 
 ?>
 --EXPECT--
-int(6)
+int(42)
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index 95342cc8e2..205704a634 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -3954,6 +3954,12 @@ int zend_try_compile_special_func(znode *result, zend_string *lcname, zend_ast_l
 		return FAILURE;
 	}
 
+	if (fbc->type != ZEND_INTERNAL_FUNCTION) {
+		/* If the function is part of disabled_functions, it may be redeclared as a userland
+		 * function with a different implementation. Don't use the VM builtin in that case. */
+		return FAILURE;
+	}
+
 	if (zend_args_contain_unpack(args)) {
 		return FAILURE;
 	}
-- 
2.40.0