php-in-php: libxml error buffer — libxml_use_internal_errors/get_errors/clear_errors without host libxml (ext/libxml)

[PurHur]

Category

php-in-php | stdlib

Problem

DOM/SimpleXML loaders (#3337, #3338) need libxml_use_internal_errors(), libxml_get_errors(), and libxml_clear_errors() to capture parse failures instead of emitting warnings. These are undefined on bin/vm.php today, forcing host libxml calls or silent parse failures during self-host.

php-src registers them in ext/libxml — not scattered C in runtime/.

php-src reference

• php/php-src ext/libxml/libxml.c — PHP_FUNCTION(libxml_use_internal_errors), libxml_get_errors, libxml_clear_errors
• php/php-src ext/libxml/libxml_error.c — LibXMLError object

Repro

./script/docker-exec.sh -- php bin/vm.php -r '
echo function_exists("libxml_use_internal_errors") ? "yes" : "no", PHP_EOL;
echo class_exists("LibXMLError") ? "yes" : "no", PHP_EOL;
'

Observed: both no

Zend PHP expected: both yes; invalid XML returns errors array when internal errors enabled.

Scope (this repo)

• ext/libxml/ module skeleton (mirror Bootstrap: ext/filter/ module skeleton — register filter_var/filter_list for self-host (M4) #5839 filter skeleton / Bootstrap: ext/intl/ module skeleton — register intl classes for self-host (M4) #5774 intl skeleton)
• PHP error ring buffer + LibXMLError class; optional thin FFI to host libxml only for bootstrap until native parser lands
• Register libxml_set_streams_context() later under same module
• Shrink goal: no new permanent runtime/libxml_*.c tables — behavior in ext/libxml/*.php

Done when

• libxml_use_internal_errors(true) suppresses warnings; libxml_get_errors() returns LibXMLError[] for malformed XML load attempt
• libxml_clear_errors() empties buffer
• Self-host probe: class_exists('LibXMLError') true without Zend PHP in loop
• test/compliance/cases/stdlib/libxml_internal_errors.phpt green on VM
• ./script/docker-exec.sh -- vendor/bin/phpunit --filter LibxmlInternalErrors

Links

• Stdlib: ext/zip — ZipArchive open/add/extract (ext/zip parity) #3337 ext/dom · Stdlib: ext/simplexml — SimpleXMLElement load/loadString (ext/simplexml parity) #3338 simplexml · Stdlib: dom_import_simplexml() / simplexml_import_dom() — DOM↔SimpleXML bridge missing (ext/dom, ext/simplexml) #6057 dom_import bridge · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: PHP Runtime → PHP — starting this run (#6058: ext/libxml error buffer + LibXMLError class, no runtime/*.c growth).

[PurHur]

Merged via #7698.

PHP-in-PHP: ext/libxml/VmLibxml.php + libxml_*.php builtins; LibXMLError registered in ext/libxml/BuiltinClasses.php. Malformed xml_parse() feeds the buffer via ext/xml/VmXml.php.

C shrink: 0 lines added to runtime/ or lib/AOT/runtime/; removed dead ext/xml/XmlFunction.php (29 lines).

Verification (green):

• Repro: function_exists('libxml_use_internal_errors') / class_exists('LibXMLError') → yes
• vendor/bin/phpunit test/unit/LibxmlInternalErrorsTest.php → OK (4 tests)
• vendor/bin/phpunit --filter libxml_internal_errors → OK (VM + JIT compliance)