[ xdebug ] Configure xdebug for PhpStorm compatibility

[mho22]

Motivation for the change, related issues

This pull request aims to add and modify Xdebug related elements in order for Xdebug with PHP.wasm ASYNCIFY to run step debugging in PHPStorm without crashing.

Implementation details

• Correction of two crashes with Error [RuntimeError]: unreachable by adding :

+ zend_observer_fcall_end_prechecked
+ zend_throw_exception_object

• Correction of one crash with Error [RuntimeError]: null function or function signature mismatch by removing :

- 'xdebug.start_upon_error=yes'

That setting was not necessary after all :

Initialize a debugging session when a PHP Notice or Warning is emitted, or when a Throwable is thrown.

• Some refactoring to maintain consistency across build.js files

[mho22]

I will need to rebuild every version of PHP.wasm Node JSPI and ASYNCIFY.

[adamziel]

For the record : It is currently not possible to use Xdebug with PHP.wasm in JSPI mode in PHPStorm since it asks for invoke_iiii when debugging server is on. It returns the following error :

I was curious what other exports we might be missing so I've inspected xdebug.so with wasm2wat and got these imports:

> wasm2wat packages/php-wasm /node/jspi/extensions/xdebug/8_4/xdebug.so | grep '(import' | grep '"env"' | awk '{print $3}' | sort | tee xdebug-imports.txt
  (import "env" "zend_get_module_version" (func (;0;) (type 2)))
  (import "env" "zend_register_ini_entries_ex" (func (;1;) (type 4)))
  (import "env" "zend_error" (func (;2;) (type 5)))
  (import "env" "getenv" (func (;3;) (type 2)))
  (import "env" "strchr" (func (;4;) (type 3)))
...200 lines...

(I am only keeping the imports coming from "env" as that's the one that are not shipped with xdebug itself).

Then I got the list of exports from PHP 8.4 JSPI:

$ wasm2wat --enable-all packages/php-wasm/node/jspi/8_4_13/php_8_4.wasm | grep '(export'  | awk '{print $2}' | sort | tee php-exports.txt 
  (export "__wasm_call_ctors" (func $__wasm_call_ctors))
  (export "php_time" (func $php_time))
  (export "gettimeofday" (func $__gettimeofday))
  (export "time" (func $__time))
  (export "php_date_get_date_ce" (func $php_date_get_date_ce))
  (export "php_date_get_immutable_ce" (func $php_date_get_immutable_ce))
  (export "php_date_get_interface_ce" (func $php_date_get_interface_ce))
  (export "php_date_get_timezone_ce" (func $php_date_get_timezone_ce))
...20k lines...

Then I computed a list of "env" xdebug imports that don't have a corresponding env export:

$  grep -v -f php-exports.txt xdebug-imports.txt
"__indirect_function_table"
"__memory_base"
"__stack_pointer"
"__table_base"
"emscripten_longjmp"
"exit"
"getaddrinfo"
"invoke_ii"
"invoke_iiii"
"invoke_iiiiii"
"invoke_v"
"memory"
"wasm_recv"
"wasm_setsockopt"

It seems like "wasm_setsockopt", "wasm_recv", etc. are taken care of by the runtime – since we're able to connect to XDebug. That leaves us with a bunch of invoke_* calls.

[adamziel]

It seems we're building XDebug without -sSUPPORT_LONGJMP=wasm -fwasm-exceptions which is why it relies on invoke_* calls. Did we try using those build options there?

[adamziel]

I've added those flags and the build seems to have worked, let me try it in phpstorm 🤞

[adamziel]

It worked! I'll rebuild all JSPI extensions

[mho22]

This is fantastic! I should have thought of that. Thank you @adamziel. Do you think this can be considered ready to be merged?

[adamziel]

🚢