Merge branch 'lightweight-functions'

Add support for lightweight functions or "lightfuncs", a plain tagged type
that contains a Duktape/C function and 16-bit flags which contain an 8-bit
signed magic value, 4-byte argument count (with 15 indicating varargs) and
a 4-byte virtual "length" property.  A lightfunc requires no heap allocations,
so it is useful in low memory environments to reduce RAM footprint.

Lightfuncs can be pushed on the value stack using the new API call
duk_push_c_lightfunc().

Also add DUK_OPT_LIGHTFUNC_BUILTINS feature option which causes Duktape to
convert all built-in functions (like Math.cos) into lightfuncs.  This saves
around 14 kB of initial RAM usage (which is about 45kB before the change)
on 32-bit environments, which is useful for at least devices with 128kB
system RAM.

Lightfuncs don't interact well with the non-standard "caller" property
(DUK_OPT_NONSTD_FUNC_CALLER_PROPERTY) so you shouldn't use them at all
if you enable that option.

If you don't use lightfuncs or enable DUK_OPT_LIGHTFUNC_BUILTINS, there
should be no visible changes, except changes in some error message strings.
Internally there are a lot of changes, especially in call handling.

.gitignore

@@ -34,5 +34,7 @@ xmldoc
 FlameGraph
 dtrace4linux
 flow
+massif-*.out
+ms_print.*
 alljoyn-js
 ajtcl

Makefile

@@ -211,6 +211,7 @@ CCOPTS_FEATURES += -DDUK_OPT_DEBUG_BUFSIZE=512
 #CCOPTS_FEATURES += -DDUK_OPT_NO_ES6_PROXY
 #CCOPTS_FEATURES += -DDUK_OPT_NO_ZERO_BUFFER_DATA
 #CCOPTS_FEATURES += -DDUK_OPT_USER_INITJS='"this.foo = 123"'
+#CCOPTS_FEATURES += -DDUK_OPT_LIGHTFUNC_BUILTINS
 CCOPTS_FEATURES += -DDUK_CMDLINE_FANCY
 CCOPTS_FEATURES += -DDUK_CMDLINE_ALLOC_LOGGING
 CCOPTS_FEATURES += -DDUK_CMDLINE_ALLOC_TORTURE
@@ -228,6 +229,7 @@ CCOPTS_SHARED += -I./dist/src -I./dist/examples/alloc-logging -I./dist/examples/
 CCOPTS_NONDEBUG = $(CCOPTS_SHARED) $(CCOPTS_FEATURES)
 CCOPTS_NONDEBUG += -Os -fomit-frame-pointer -g -ggdb
 #CCOPTS_NONDEBUG += -DDUK_OPT_ASSERTIONS
+
 CCOPTS_DEBUG = $(CCOPTS_SHARED) $(CCOPTS_FEATURES)
 CCOPTS_DEBUG += -O0 -g -ggdb
 CCOPTS_DEBUG += -DDUK_OPT_DEBUG
@@ -294,6 +296,7 @@ clean:
 	@rm -rf luajs
 	@rm -f dukweb.js
 	@rm -rf /tmp/dukweb-test/
+	@rm -f massif-*.out
 
 .PHONY: cleanall
 cleanall: clean
@@ -794,6 +797,7 @@ ajduk: alljoyn-js ajtcl dist
 		$(CCOPTS_NONDEBUG) \
 		-m32 \
 		-UDUK_CMDLINE_FANCY -DDUK_CMDLINE_AJSHEAP -D_POSIX_C_SOURCE=200809L \
+		-DDUK_OPT_LIGHTFUNC_BUILTINS \
 		$(DUKTAPE_SOURCES) $(DUKTAPE_CMDLINE_SOURCES) \
 		alljoyn-js/ajs_heap.c ajtcl/src/aj_debug.c ajtcl/target/linux/aj_target_util.c \
 		-lm -lpthread
@@ -888,3 +892,23 @@ codepolicycheckvim:
 .PHONY: big-git-files
 big-git-files:
 	util/find_big_git_files.sh
+
+# Simple heap graph and peak usage using valgrind --tool=massif, for quick
+# and dirty baseline comparison.  Say e.g. 'make massif-test-dev-hello-world'.
+# The target name is intentionally not 'massif-%.out' so that the rule is never
+# satisfied and can be executed multiple times without cleaning.
+# Grep/sed hacks from:
+# http://stackoverflow.com/questions/774556/peak-memory-usage-of-a-linux-unix-process
+massif-%: ecmascript-testcases/%.js duk
+	@rm -f $(@).out
+	valgrind --tool=massif --peak-inaccuracy=0.0 --massif-out-file=$(@).out ./duk $< >/dev/null 2>/dev/null
+	@ms_print $(@).out | head -35
+	@echo "[... clipped... ]"
+	@echo ""
+	@echo -n "MAXIMUM: "
+	@cat $(@).out | grep mem_heap_B | sed -e 's/mem_heap_B=\(.*\)/\1/' | sort -g | tail -n 1
+
+# Convenience targets
+massif-helloworld: massif-test-dev-hello-world
+massif-deepmerge: massif-test-dev-deepmerge
+massif-arcfour: massif-test-dev-arcfour

RELEASES.rst

@@ -627,6 +627,18 @@ Planned
 * Main release goal: improved low memory support to allow Duktape to run
   better on devices with 128kB system memory
 
+* Add lightfunc (DUK_TYPE_LIGHTFUNC) primitive type, representing a
+  Duktape/C function with a plain tagged value without any heap allocations
+
+* Add duk_push_c_lightfunc() API call to push user lightfuncs on the
+  value stack
+
+* Add duk_is_lightfunc() API call to type check for lightfuncs
+
+* Add feature option DUK_OPT_LIGHTFUNC_BUILTINS which causes Duktape to use
+  lightfuncs for almost all built-in functions, saving around 14kB of Duktape
+  heap on 32-bit platforms
+
 * Add duk_is_error() API call to check if a value inherits from Error
 
 * Add duk_get_error_code() API call to check if a value inherits from