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Fix GH-20906: Assertion failure when messing up output buffers #20908

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Fix GH-20906: Assertion failure when messing up output buffers #20908

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cc489ea
Fix GH-20906: Assertion failure when messing up output buffers
ndossche Jan 11, 2026
f655a8f
unexpected
ndossche Jan 11, 2026
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15 changes: 12 additions & 3 deletions ext/standard/basic_functions.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1768,7 +1768,10 @@ PHP_FUNCTION(highlight_file)
}

if (i) {
php_output_start_default();
if (UNEXPECTED(php_output_start_default() != SUCCESS)) {
zend_throw_error(NULL, "Unable to start output handler");
RETURN_THROWS();
}
}

php_get_highlight_struct(&syntax_highlighter_ini);
Expand Down Expand Up @@ -1803,7 +1806,10 @@ PHP_FUNCTION(php_strip_whitespace)
Z_PARAM_PATH_STR(filename)
ZEND_PARSE_PARAMETERS_END();

php_output_start_default();
if (UNEXPECTED(php_output_start_default() != SUCCESS)) {
zend_throw_error(NULL, "Unable to start output handler");
RETURN_THROWS();
}

zend_stream_init_filename_ex(&file_handle, filename);
zend_save_lexical_state(&original_lex_state);
Expand Down Expand Up @@ -1840,7 +1846,10 @@ PHP_FUNCTION(highlight_string)
ZEND_PARSE_PARAMETERS_END();

if (i) {
php_output_start_default();
if (UNEXPECTED(php_output_start_default() != SUCCESS)) {
zend_throw_error(NULL, "Unable to start output handler");
RETURN_THROWS();
}
}

EG(error_reporting) = E_ERROR;
Expand Down
25 changes: 25 additions & 0 deletions ext/standard/tests/strings/gh20906_1.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
--TEST--
GH-20906 (Assertion failure when messing up output buffers) - php_strip_whitespace
--CREDITS--
vi3tL0u1s
--FILE--
<?php
class A {
function __destruct() {
php_strip_whitespace(__FILE__);
echo "x";
$c = new A;
ob_start(function () use ($c) { return '/'; }, 1);
ob_start(function () use (&$c) { $c = new A; return '/'; }, 1);
}
}

try {
new A;
} catch (Throwable $e) {
echo $e::class, ": ", $e->getMessage(), "\n";
}
?>
--EXPECTF--
%a
Fatal error: php_strip_whitespace(): Cannot use output buffering in output buffering display handlers in %s on line %d
21 changes: 21 additions & 0 deletions ext/standard/tests/strings/gh20906_2.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
--TEST--
GH-20906 (Assertion failure when messing up output buffers) - highlight_file
--CREDITS--
vi3tL0u1s
--FILE--
<?php
class A {
function __destruct() {
highlight_file(__FILE__, true);
echo "x";
$c = new A;
ob_start(function () use ($c) { return '/'; }, 1);
ob_start(function () use (&$c) { $c = new A; return '/'; }, 1);
}
}

new A;
?>
--EXPECTF--
%a
Fatal error: highlight_file(): Cannot use output buffering in output buffering display handlers in %s on line %d
21 changes: 21 additions & 0 deletions ext/standard/tests/strings/gh20906_3.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
--TEST--
GH-20906 (Assertion failure when messing up output buffers) - highlight_string
--CREDITS--
vi3tL0u1s
--FILE--
<?php
class A {
function __destruct() {
highlight_string(__FILE__, true);
echo "x";
$c = new A;
ob_start(function () use ($c) { return '/'; }, 1);
ob_start(function () use (&$c) { $c = new A; return '/'; }, 1);
}
}

new A;
?>
--EXPECTF--
%a
Fatal error: highlight_string(): Cannot use output buffering in output buffering display handlers in %s on line %d
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