Test gh20836_stack_limit.phpt fails on Alpinelinux ppc64le 8.4.18RC1

[andypost]

Description

Testing upcoming release 8.4.18RC1 and se reproducible failure, only on ppc64le arch

The diff is:

TEST 9720/19044 [ext/mbstring/tests/gh20836_stack_limit.phpt]
========DIFF========
001- Fatal error: Uncaught Error: Maximum call stack size of %d bytes (zend.max_allowed_stack_size - zend.reserved_stack_size) reached. Infinite recursion? in %s:%d
002- Stack trace:
003- #0 %s(%d): mb_convert_variables('utf-8', 'utf-8', Array)
004- #1 {main}
005-   thrown in %s on line %d
001+ Fatal error: Maximum call stack size of 81920 bytes (zend.max_allowed_stack_size - zend.reserved_stack_size) reached during compilation. Try splitting expression in /builds/alpine/aports/community/php84/src/php-8.4.18RC1/ext/mbstring/tests/gh20836_stack_limit.php on line 4
========DONE========
FAIL GH-20836 (Stack overflow in mb_convert_variables with recursive array references, stack limit case) [ext/mbstring/tests/gh20836_stack_limit.phpt] 

PHP Version

PHP 8.4.18RC1

Operating System

Alpinelinux

[andypost]

ref https://gitlab.alpinelinux.org/alpine/aports/-/jobs/2196635

[iluuu1994]

@alexandre-daubois The max_allowed_stack_size might need tweaking so this doesn't fail during compilation.

[andypost]

The question is it expected behavior as Alpinelinux using Musl which stack size is 128 KB by default but I never faced this limit and not sure I need to increase it in linker

[alexandre-daubois]

I wonder if this could work:

diff --git a/ext/mbstring/tests/gh20836_stack_limit.phpt b/ext/mbstring/tests/gh20836_stack_limit.phpt
index b58833ff80c..8e5500bf8c1 100644
--- a/ext/mbstring/tests/gh20836_stack_limit.phpt
+++ b/ext/mbstring/tests/gh20836_stack_limit.phpt
@@ -16,16 +16,11 @@
 --FILE--
 <?php
 
-function createDeepArray($depth) {
-    if ($depth <= 0) {
-        return 'deep value';
-    }
-    return ['nested' => createDeepArray($depth - 1)];
+$deepArray = 'deep value';
+for ($i = 0; $i < 15000; $i++) {
+    $deepArray = ['nested' => $deepArray];
 }
 
-// Create a deeply nested array that will trigger stack limit
-$deepArray = createDeepArray(15000);
-
 mb_convert_variables('utf-8', 'utf-8', $deepArray);
 
 echo "Done\n";

This replaces the recursive createDeepArray(15000) function with a loop that builds the same deeply nested array structure without consuming stack space. Would you have a way to try this and see if it fixes the issue?

[iluuu1994]

Not sure, the error indicates the limit is reached during compilation, rather than execution of createDeepArray(). Recursion of PHP functions does not cause recursion on the C stack. Optimally we could disable the stack limit for compilation entirely for these tests, but that's not trivial given zend.max_allowed_stack_size is ZEND_INI_SYSTEM and can't be changed at runtime.