javascript: Rework Makefile and GC so it works with latest Emscripten.

The GC now works correctly using asyncify and the functions
emscripten_scan_stack() and emscripten_scan_registers().  Stack/call depth
is monitored via the use of the pystack option.

Fixes issue #6738.

Signed-off-by: Damien George <damien@micropython.org>

ports/javascript/Makefile

@@ -6,24 +6,16 @@ QSTR_DEFS = qstrdefsport.h
 
 include $(TOP)/py/py.mk
 
-CC = emcc -g4
-LD = emcc -g4
+CC = emcc
+LD = emcc
 
 INC += -I.
 INC += -I$(TOP)
 INC += -I$(BUILD)
 
-CPP = clang -E
-
-ifdef EMSCRIPTEN
-    CPP += -isystem $(EMSCRIPTEN)/system/include/libc -cxx-isystem $(EMSCRIPTEN)/system/include/libcxx
-endif
-
-CFLAGS = -m32 -Wall -Werror -Wdouble-promotion -Wfloat-conversion $(INC) -std=c99 $(COPT)
-LDFLAGS = -m32 -Wl,-Map=$@.map,--cref -Wl,--gc-sections
-
-CFLAGS += -O0 -DNDEBUG
-CFLAGS += -fdata-sections -ffunction-sections
+CFLAGS += -std=c99 -Wall -Werror -Wdouble-promotion -Wfloat-conversion
+CFLAGS += -O3 -DNDEBUG
+CFLAGS += $(INC)
 
 ifneq ($(FROZEN_MPY_DIR),)
 # To use frozen bytecode, put your .py files in a subdirectory (eg frozen/) and
@@ -46,12 +38,12 @@ SRC_C = \
 
 SRC_QSTR += $(SRC_C)
 
-OBJ = 
-OBJ = $(PY_O) 
+OBJ += $(PY_O)
 OBJ += $(addprefix $(BUILD)/, $(SRC_LIB:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 
-JSFLAGS = -O0 -s EXPORTED_FUNCTIONS="['_mp_js_init', '_mp_js_init_repl', '_mp_js_do_str', '_mp_js_process_char', '_mp_hal_get_interrupt_char', '_mp_sched_keyboard_interrupt']" -s EXTRA_EXPORTED_RUNTIME_METHODS="['ccall', 'cwrap']" -s "BINARYEN_TRAP_MODE='clamp'" --memory-init-file 0 --js-library library.js
+JSFLAGS += -s ASYNCIFY
+JSFLAGS += -s EXPORTED_FUNCTIONS="['_mp_js_init', '_mp_js_init_repl', '_mp_js_do_str', '_mp_js_process_char', '_mp_hal_get_interrupt_char', '_mp_sched_keyboard_interrupt']" -s EXTRA_EXPORTED_RUNTIME_METHODS="['ccall', 'cwrap']" -s --memory-init-file 0 --js-library library.js
 
 all: $(BUILD)/micropython.js
 
@@ -65,6 +57,6 @@ min: $(BUILD)/micropython.js
 
 test: $(BUILD)/micropython.js $(TOP)/tests/run-tests.py
 	$(eval DIRNAME=ports/$(notdir $(CURDIR)))
-	cd $(TOP)/tests && MICROPY_MICROPYTHON=../ports/javascript/node_run.sh ./run-tests.py
+	cd $(TOP)/tests && MICROPY_MICROPYTHON=../ports/javascript/node_run.sh ./run-tests.py -j1
 
 include $(TOP)/py/mkrules.mk

ports/javascript/README.md

@@ -7,17 +7,7 @@ Dependencies
 ------------
 
 Building micropython.js bears the same requirements as the standard MicroPython
-ports with the addition of Emscripten (and uglify-js for the minified file). 
-
-A standard installation of Emscripten should provide functional code, however
-if memory errors are encountered it may be worthwhile to modify the tool.
-`emscripten-fastcomp/lib/Target/JSBackend.cpp` may require the minor fix 
-found in JSBackend.patch. This patch attempts to address situations where
-C code running through Emscripten is denied access to Javascript variables 
-leading to false-positives in the MicroPython garbage collector as variables 
-with pointers exclusively in Javascript will be erased prematurely.
-Refer to Emscripten documentation for instructions on building Emscripten 
-from source.
+ports with the addition of Emscripten (and uglify-js for the minified file).
 
 Build instructions
 ------------------
@@ -39,15 +29,15 @@ Access the repl with:
 
 Stack size may be modified using:
 
-	$ node build/micropython.js -X stack=64K
+    $ node build/micropython.js -X stack=64K
 
 Where stack size may be represented in Bytes, KiB or MiB.
 
 MicroPython scripts may be executed using:
 
-	$ node build/micropython.js hello.py
+    $ node build/micropython.js hello.py
 
-Alternatively micropython.js may by accessed by other javascript programs in node 
+Alternatively micropython.js may by accessed by other javascript programs in node
 using the require command and the general API outlined below. For example:
 
 ```javascript
@@ -85,7 +75,7 @@ demonstrates basic functionality:
 ```
 
 MicroPython code execution will suspend the browser so be sure to atomize usage
-within this environment. Unfortunately interrupts have not been implemented for the 
+within this environment. Unfortunately interrupts have not been implemented for the
 browser.
 
 Testing
@@ -124,5 +114,5 @@ the repl.
 mp_js_process_char(char)
 ```
 
-Input character into MicroPython repl. `char` must be of type `number`. This 
+Input character into MicroPython repl. `char` must be of type `number`. This
 will execute MicroPython code when necessary.

ports/javascript/main.c

@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2013, 2014 Damien P. George and 2017, 2018 Rami Ali
+ * Copyright (c) 2013-2021 Damien P. George and 2017, 2018 Rami Ali
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -36,6 +36,7 @@
 #include "py/mperrno.h"
 #include "lib/utils/pyexec.h"
 
+#include "emscripten.h"
 #include "library.h"
 
 #if MICROPY_ENABLE_COMPILER
@@ -70,8 +71,6 @@ int do_str(const char *src, mp_parse_input_kind_t input_kind) {
 }
 #endif
 
-static char *stack_top;
-
 int mp_js_do_str(const char *code) {
     return do_str(code, MP_PARSE_FILE_INPUT);
 }
@@ -81,9 +80,6 @@ int mp_js_process_char(int c) {
 }
 
 void mp_js_init(int heap_size) {
-    int stack_dummy;
-    stack_top = (char *)&stack_dummy;
-
     #if MICROPY_ENABLE_GC
     char *heap = (char *)malloc(heap_size * sizeof(char));
     gc_init(heap, heap + heap_size);
@@ -105,15 +101,14 @@ void mp_js_init_repl() {
     pyexec_event_repl_init();
 }
 
+STATIC void gc_scan_func(void *begin, void *end) {
+    gc_collect_root((void **)begin, (void **)end - (void **)begin + 1);
+}
+
 void gc_collect(void) {
-    // WARNING: This gc_collect implementation doesn't try to get root
-    // pointers from CPU registers, and thus may function incorrectly.
-    jmp_buf dummy;
-    if (setjmp(dummy) == 0) {
-        longjmp(dummy, 1);
-    }
     gc_collect_start();
-    gc_collect_root((void *)stack_top, ((mp_uint_t)(void *)(&dummy + 1) - (mp_uint_t)stack_top) / sizeof(mp_uint_t));
+    emscripten_scan_stack(gc_scan_func);
+    emscripten_scan_registers(gc_scan_func);
     gc_collect_end();
 }