[PHP-wasm] Add support for concurrent popen calls

packages/php-wasm/compile/php/Dockerfile

@@ -455,19 +455,9 @@ RUN /root/replace.sh 's/ret = read/ret = wasm_read/g' /root/php-src/main/streams
 # to an unused identifier "php_exec_old", and then we mark php_exec as extern.
 RUN /root/replace.sh 's/PHPAPI int php_exec(.+)$/PHPAPI extern int php_exec\1; int php_exec_old\1/g' /root/php-src/ext/standard/exec.c
 
-# Provide a custom implementation of the VCWD_POPEN() function that handles spawning
-# the process inside PHP_FUNCTION(popen).
-RUN /root/replace.sh 's/#define VCWD_POPEN.+/#define VCWD_POPEN(command, type) wasm_popen(command,type)/g' /root/php-src/Zend/zend_virtual_cwd.h
-RUN echo 'extern FILE *wasm_popen(const char *cmd, const char *mode);' >> /root/php-src/Zend/zend_virtual_cwd.h
-
-# Patch mail.c for Emscripten compatibility:
-# 1. Use VCWD_POPEN (routed through wasm_popen) instead of raw popen(),
-#    so that PHP's mail() function goes through our JS spawn handler.
-# 2. Use wasm_pclose() instead of pclose() so we wait for the spawned
-#    process to finish and get a correct exit code. Libc's pclose() doesn't
-#    work with FILE handles created by wasm_popen (fdopen).
-RUN sed -i '1i #include <stdio.h>\nextern int wasm_pclose(FILE *fp);' /root/php-src/ext/standard/mail.c
-RUN perl -pi.bak -e 's/\bpopen\s*\(\s*sendmail_cmd\s*,/VCWD_POPEN(sendmail_cmd,/g; s/\bpclose\s*\(\s*sendmail\s*\)/wasm_pclose(sendmail)/g' /root/php-src/ext/standard/mail.c
+# popen() and pclose() are redirected to wasm_popen/wasm_pclose at link
+# time via -Wl,--wrap=popen and -Wl,--wrap=pclose (see linker flags below).
+# This covers all call sites including PHP's popen() function and mail().
 
 # Provide a custom implementation of the shutdown() function.
 RUN perl -pi.bak -e $'s/(\s+)shutdown\(/$1 wasm_shutdown(/g' /root/php-src/sapi/cli/php_cli_server.c
@@ -1676,6 +1666,8 @@ RUN export ASYNCIFY_IMPORTS=$'[\n\
 "wasm_php_stream_read",\
 "wasm_pclose",\
 "wasm_popen",\
+"__wrap_pclose",\
+"__wrap_popen",\
 "wasm_read",\
 "wasm_sapi_handle_request",\
 "wasm_sapi_request_shutdown",\
@@ -2040,6 +2032,7 @@ RUN export ASYNCIFY_IMPORTS=$'[\n\
 "zif_phar_file_get_contents",\
 "zif_phar_fopen",\
 "zif_mail",\
+"zif_pclose",\
 "zif_popen",\
 "zif_post_message_to_js",\
 "zif_preg_replace_callback",\
@@ -2246,7 +2239,7 @@ RUN set -euxo pipefail; \
 	source /root/emsdk/emsdk_env.sh; \
 	if [ "$WITH_JSPI" = "yes" ]; then \
 		# Both imports and exports are required for inter-module communication with wrapped methods, e.g., wasm_recv.
-		export ASYNCIFY_FLAGS=" -s ASYNCIFY=2 -sSUPPORT_LONGJMP=wasm -fwasm-exceptions -sJSPI_IMPORTS=js_open_process,js_fd_read,js_waitpid,js_process_status,js_create_input_device,wasm_setsockopt,wasm_shutdown,wasm_close,wasm_recv,wasm_connect,__syscall_fcntl64,js_flock,js_release_file_locks,js_waitpid -sJSPI_EXPORTS=php_wasm_init,wasm_sleep,wasm_read,emscripten_sleep,wasm_sapi_handle_request,wasm_sapi_request_shutdown,wasm_poll_socket,wrap_select,__wrap_select,select,php_pollfd_for,fflush,wasm_popen,wasm_pclose,wasm_read,wasm_php_exec,run_cli,wasm_recv,wasm_connect,__wasm_call_ctors,__errno_location,__funcs_on_exit -s EXPORTED_RUNTIME_METHODS=HEAPU32,HEAPU8,ccall,PROXYFS,wasmExports "; \
+		export ASYNCIFY_FLAGS=" -s ASYNCIFY=2 -sSUPPORT_LONGJMP=wasm -fwasm-exceptions -sJSPI_IMPORTS=js_open_process,js_fd_read,js_waitpid,js_process_status,js_create_input_device,wasm_setsockopt,wasm_shutdown,wasm_close,wasm_recv,wasm_connect,__syscall_fcntl64,js_flock,js_release_file_locks,js_waitpid -sJSPI_EXPORTS=php_wasm_init,wasm_sleep,wasm_read,emscripten_sleep,wasm_sapi_handle_request,wasm_sapi_request_shutdown,wasm_poll_socket,wrap_select,__wrap_select,select,php_pollfd_for,fflush,wasm_popen,wasm_pclose,__wrap_popen,__wrap_pclose,wasm_read,wasm_php_exec,run_cli,wasm_recv,wasm_connect,__wasm_call_ctors,__errno_location,__funcs_on_exit -s EXPORTED_RUNTIME_METHODS=HEAPU32,HEAPU8,ccall,PROXYFS,wasmExports "; \
 		echo '#define PLAYGROUND_JSPI 1' > /root/php_wasm_asyncify.h; \
 	else \
 		export ASYNCIFY_FLAGS=" -s ASYNCIFY=1 -s ASYNCIFY_IGNORE_INDIRECT=1 -s EXPORTED_RUNTIME_METHODS=HEAPU32,HEAPU8,ccall,PROXYFS,wasmExports,UTF8ToString,lengthBytesUTF8,stringToUTF8 $(cat /root/.emcc-php-asyncify-flags) "; \
@@ -2302,6 +2295,8 @@ RUN set -euxo pipefail; \
 	-Wl,@/root/.wasm-exports \
 	-Wl,--wrap=usleep \
 	-Wl,--wrap=select \
+	-Wl,--wrap=popen \
+	-Wl,--wrap=pclose \
 		/root/lib/libphp.a \
 		/root/proc_open.c \
 		/root/php_wasm.c \

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

@@ -427,12 +427,9 @@ EM_JS(__wasi_errno_t, js_fd_read, (__wasi_fd_t fd, const __wasi_iovec_t *iov, si
 });
 extern int __wasi_syscall_ret(__wasi_errno_t code);
 
-// Exit code of the last exited child process call.
-int wasm_pclose_ret = -1;
-
-// PID of the last process spawned by wasm_popen("w").
-// Used by wasm_pclose to wait for the process to finish.
-static int wasm_popen_last_pid = -1;
+extern void js_popen_set_pid_for_fd(int fd, int pid);
+extern int js_popen_get_pid_for_fd(int fd);
+extern void js_popen_clear_pid_for_fd(int fd);
 
 /**
  * Passes a message to the JavaScript module and writes the response
@@ -505,7 +502,6 @@ EMSCRIPTEN_KEEPALIVE FILE *wasm_popen(const char *cmd, const char *mode)
 		char *file_path = js_popen_to_file(cmd, mode, &last_exit_code);
 		fp = fopen(file_path, mode);
 		FG(pclose_ret) = last_exit_code;
-		wasm_pclose_ret = last_exit_code;
 	}
 	else if (*mode == 'w')
 	{
@@ -548,7 +544,7 @@ EMSCRIPTEN_KEEPALIVE FILE *wasm_popen(const char *cmd, const char *mode)
 		descv[1] = stdout;
 		descv[2] = stderr;
 
-		wasm_popen_last_pid = js_open_process(
+		int pid = js_open_process(
 			cmd,
 			NULL,
 			0,
@@ -559,6 +555,7 @@ EMSCRIPTEN_KEEPALIVE FILE *wasm_popen(const char *cmd, const char *mode)
 			0,
 			0
 		);
+		js_popen_set_pid_for_fd(fileno(fp), pid);
 
 		efree(stdin);
 		efree(stdout);
@@ -579,29 +576,41 @@ EMSCRIPTEN_KEEPALIVE FILE *wasm_popen(const char *cmd, const char *mode)
 /**
  * Close a FILE* created by wasm_popen and wait for the spawned process
  * to exit. Returns the process exit code, or -1 on error.
- *
- * @TODO wasm_popen_last_pid and wasm_pclose_ret are single globals,
- * so concurrent writable popen() calls will clobber each other's
- * PID and exit code. Safe today because mail() is the only caller
- * and it does a strict open-write-close sequence, but a proper fix
- * would stash both in a table keyed by fd.
  */
 extern int js_waitpid(int pid, int *exitcode);
 
 EMSCRIPTEN_KEEPALIVE int wasm_pclose(FILE *fp)
 {
-	int pid = wasm_popen_last_pid;
+	int pid = js_popen_get_pid_for_fd(fileno(fp));
+	js_popen_clear_pid_for_fd(fileno(fp));
 	fclose(fp);
 	if (pid < 0) {
 		return -1;
 	}
 	int wstatus = 0;
 	js_waitpid(pid, &wstatus);
-	wasm_pclose_ret = wstatus;
 	FG(pclose_ret) = wstatus;
 	return wstatus;
 }
 
+/**
+ * Linker-level wrappers so every call to popen()/pclose() in the
+ * compiled C code is redirected here via -Wl,--wrap=popen/pclose.
+ */
+FILE *__wrap_popen(const char *cmd, const char *mode)
+{
+	return wasm_popen(cmd, mode);
+}
+
+extern int __real_pclose(FILE *fp);
+int __wrap_pclose(FILE *fp)
+{
+	if (js_popen_get_pid_for_fd(fileno(fp)) >= 0) {
+		return wasm_pclose(fp);
+	}
+	return __real_pclose(fp);
+}
+
 /**
  * Ship php_exec, the function powering the following PHP
  * functions:
@@ -767,7 +776,7 @@ EMSCRIPTEN_KEEPALIVE int wasm_php_exec(int type, const char *cmd, zval *array, z
 	pclose_return = php_stream_close(stream);
 	if (pclose_return == -1)
 	{
-		pclose_return = wasm_pclose_ret;
+		pclose_return = FG(pclose_ret);
 	}
 	efree(buf);
 

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

@@ -950,6 +950,30 @@ const LibraryExample = {
 		});
 	},
 
+	js_popen_set_pid_for_fd: function (fd, pid) {
+		if (PHPWASM.processTable[pid]) {
+			PHPWASM.processTable[pid].fd = fd;
+		}
+	},
+
+	js_popen_get_pid_for_fd: function (fd) {
+		for (const pid in PHPWASM.processTable) {
+			if (PHPWASM.processTable[pid].fd === fd) {
+				return PHPWASM.processTable[pid].pid;
+			}
+		}
+		return -1;
+	},
+
+	js_popen_clear_pid_for_fd: function (fd) {
+		for (const pid in PHPWASM.processTable) {
+			if (PHPWASM.processTable[pid].fd === fd) {
+				delete PHPWASM.processTable[pid].fd;
+				return;
+			}
+		}
+	},
+
 	/**
 	 * Shims unix shutdown(2) functionality for asynchronous:
 	 * https://man7.org/linux/man-pages/man2/shutdown.2.html