php-in-php: json_decode() — delete phpc_json_decode.c (~649 lines), VM+JIT+AOT from ext/standard/VmJson*.php #6202

Category

php-in-php | bootstrap

Problem

json_decode() still depends on a hand-written C parser in lib/AOT/runtime/phpc_json_decode.c (~649 lines) for JIT/AOT link, while the VM path already has PHP scanners/validators (ext/standard/VmJsonScanner.php, VmJsonValidate.php). This blocks self-host (#1492): the native binary must not ship a duplicate JSON parser in C when PHP lowering is sufficient.

PHP-in-PHP first: port decode semantics into ext/standard/ + JIT lowering; delete or shrink the C file to a thin ABI trampoline (if any remains).

php-src reference

• php/php-src ext/json/php_json_decoder.c — reference decode semantics
• php/php-src ext/json/php_json.c — json_decode() flags, depth, assoc/object modes
• php/php-src ext/standard/basic_functions.stub.php — JSON_* constants

Repro (C runtime still linked today)

./script/docker-exec.sh -- bash -lc 'wc -l lib/AOT/runtime/phpc_json_decode.c; rg -l phpc_json_decode lib/AOT/Linker.php'

lib/AOT/Linker.php lists phpc_json_decode.c; ext/standard/VmJsonScanner.php header notes it mirrors the C scanner.

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r "
\$j = json_decode(\"{\\\"a\\\":1,\\\"b\\\":[true,null]}\", true);
var_export(\$j);
"'

VM decode works; goal is same behavior without C parser on JIT/AOT/self-host paths.

Scope (this repo)

Done when

• json_decode() VM/JIT/AOT behavior matches Zend on compliance .phpt set (assoc + object modes, depth, invalid JSON)
• lib/AOT/runtime/phpc_json_decode.c removed from link (or reduced to documented thin ABI only)
• PR body lists lines removed from runtime/
• make bootstrap-selfhost-link / targeted ./script/ci-fast.sh --filter JsonDecode green

Related

• Stdlib: json_last_error() — VM + LLVM JIT/AOT #1173 JSON decode subset · Stdlib: json_decode() — enum case JSON must TypeError not LogicException (ext/json/php_json.c) #5907 enum operand TypeError · Stdlib: json_encode() — enum case operands must match Zend JSON output (ext/json/php_json.c) #6130 json_encode enum parity · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host