Fix shutdown errors (#1104)

Fixes #1078

## What is this PR doing?

If fixes an Asyncify error and memory leak when running PHP shutdown
functions.

## What problem is it solving?

It adds full support for PHP shutdown functions and prevents crashes.

## How is the problem addressed?

By adding Asyncify support for `wasm_sapi_request_shutdown` and
preventing `free` from running if memory wasn't allocated.

## Testing Instructions

- Checkout this branch
- Run dev env `npm run dev`
- [Open this
URL](http://localhost:5400/website-server/?php=8.0&wp=latest&storage=none&networking=yes#{%20%22landingPage%22:%20%22/wp-admin/%22,%20%22features%22:%20{%20%22networking%22:%20true%20},%20%22steps%22:%20[%20{%20%22step%22:%20%22login%22%20},%20{%20%22step%22:%20%22writeFile%22,%20%22path%22:%20%22/wordpress/wp-content/mu-plugins/rewrite.php%22,%20%22data%22:%20%22%3C?php%20add_action(%20'shutdown',%20function()%20{%20post_message_to_js('test');%20}%20);%22%20}%20]%20})
and confirm that WP loads without Asyncify errors and and memory leaks
(check the browser console)

Author: bgrgicak

packages/php-wasm/compile/php/Dockerfile

@@ -521,6 +521,7 @@ RUN echo -n ' -s ASYNCIFY=1 -s ASYNCIFY_IGNORE_INDIRECT=1 ' >> /root/.emcc-php-w
 "get_http_body",\
 "wasm_php_exec",\
 "wasm_sapi_handle_request",\
+"wasm_sapi_request_shutdown",\
 "_call_user_function_ex",\
 "_call_user_function_impl",\
 "_mysqlnd_run_command",\
@@ -786,6 +787,7 @@ RUN set -euxo pipefail; \
 "_wasm_add_ENV_entry", \n\
 "_wasm_read", \n\
 "_wasm_sapi_handle_request", \n\
+"_wasm_sapi_request_shutdown", \n\
 "_wasm_set_content_length", \n\
 "_wasm_set_content_type", \n\
 "_wasm_set_cookies", \n\

packages/php-wasm/compile/php/php_wasm.c

@@ -396,7 +396,7 @@ PHP_FUNCTION(post_message_to_js)
 
 	char *response;
 	size_t response_len = js_module_onMessage(data, &response);
-	if (response != NULL)
+	if (response != -1)
 	{
 		zend_string *return_string = zend_string_init(response, response_len, 0);
 		free(response);

packages/php-wasm/compile/php/phpwasm-emscripten-library.js

@@ -20,7 +20,7 @@ const LibraryExample = {
 			// stdout, stderr, and headers information are written for the JavaScript
 			// code to read later on.
 			FS.mkdir("/internal");
-			
+
 			PHPWASM.EventEmitter = ENVIRONMENT_IS_NODE
 				? require('events').EventEmitter
 				: class EventEmitter {
@@ -548,7 +548,7 @@ const LibraryExample = {
 		return Asyncify.handleSleep((wakeUp) => {
 			const poll = function () {
 				if (PHPWASM.child_proc_by_pid[pid]?.exited) {
-					HEAPU32[exitCodePtr >> 2] = 
+					HEAPU32[exitCodePtr >> 2] =
 						PHPWASM.child_proc_by_pid[pid].exitCode;
 					wakeUp(pid);
 				} else {
@@ -950,7 +950,7 @@ const LibraryExample = {
 						// separates JS context from the PHP context so we
 						// don't let PHP crash here.
 						console.error(e);
-						wakeUp(0);
+						wakeUp(-1);
 					});
 			});
 		}