Fix GH-16319: protect fiber backtrace with null filename from crashing

Author: alexandre-daubois

NEWS

@@ -14,6 +14,8 @@ PHP                                                                        NEWS
     array). (ilutov)
   . Fixed bug GH-19480 (error_log php.ini cannot be unset when open_basedir is
     configured). (nielsdos)
+  . Fixed bug GH-16319 (Prevent crash when displaying fiber backtrace with
+    a null filename). (alexandre-daubois)
 
 - Date:
   . Fixed GH-17159: "P" format for ::createFromFormat swallows string literals.

ext/zend_test/observer.c

@@ -155,7 +155,7 @@ static void observer_show_init(zend_function *fbc)
 			php_printf("%*s<!-- init %s() -->\n", 2 * ZT_G(observer_nesting_depth), "", ZSTR_VAL(fbc->common.function_name));
 		}
 	} else {
-		php_printf("%*s<!-- init '%s' -->\n", 2 * ZT_G(observer_nesting_depth), "", ZSTR_VAL(fbc->op_array.filename));
+		php_printf("%*s<!-- init '%s' -->\n", 2 * ZT_G(observer_nesting_depth), "", fbc->op_array.filename ? ZSTR_VAL(fbc->op_array.filename) : "[no active file]");
 	}
 }
 
@@ -178,7 +178,7 @@ static void observer_show_init_backtrace(zend_execute_data *execute_data)
 				php_printf("%*s%s()\n", indent, "", ZSTR_VAL(fbc->common.function_name));
 			}
 		} else {
-			php_printf("%*s{main} %s\n", indent, "", ZSTR_VAL(fbc->op_array.filename));
+			php_printf("%*s{main} %s\n", indent, "", fbc->op_array.filename ? ZSTR_VAL(fbc->op_array.filename) : "[no active file]");
 		}
 	} while ((ex = ex->prev_execute_data) != NULL);
 	php_printf("%*s-->\n", 2 * ZT_G(observer_nesting_depth), "");

ext/zend_test/tests/observer_fiber_backtrace_crash.phpt

@@ -0,0 +1,36 @@
+--TEST--
+GH-16319 (Fiber backtrace with null filename should not crash)
+--EXTENSIONS--
+zend_test
+--INI--
+zend_test.observer.enabled=1
+zend_test.observer.show_init_backtrace=1
+--FILE--
+<?php
+$fiber = new Fiber(function() {});
+$fiber->start();
+echo "Test completed without crash\n";
+?>
+--EXPECTF--
+<!-- init '%s' -->
+<!--
+    {main} %s
+-->
+<!-- init Fiber::__construct() -->
+<!--
+    Fiber::__construct()
+    {main} %s
+-->
+<!-- init Fiber::start() -->
+<!--
+    Fiber::start()
+    {main} %s
+-->
+<!-- init {closure}() -->
+<!--
+    {closure}()
+    {main} [no active file]
+    Fiber::start()
+    {main} %s
+-->
+Test completed without crash