背景

本文適合有c語言基礎的朋友，且瞭解make編譯。elk是cesanta開源社群mongoose同類產品中的javascript庫。目前支援的特性如下：

• Operations: all standard JS operations except:
  • !=, ==. Use strict comparison !==, ===
  • No computed member access a[b]
• Typeof: typeof('a') === 'string'
• While: while (...) { ... }
• Conditional: if (...) ... else ...
• Ternary operator a ? b : c
• Simple types: let a, b, c = 12.3, d = 'a', e = null, f = true, g = false;
• Functions: let f = function(x, y) { return x + y; };
• Objects: let obj = {f: function(x) { return x * 2}}; obj.f(3);
• Every statement must end with a semicolon ;
• Strings are binary data chunks, not Unicode strings: 'Київ'.length === 8

搜尋

複製

不支援的特性如下：

• No var, no const. Use let (strict mode only)
• No do, switch, for. Use while
• No => functions. Use let f = function(...) {...};
• No arrays, closures, prototypes, this, new, delete
• No standard library: no Date, Regexp, Function, String, Number

筆者在freebsd 11編譯測試過程如下，僅供參考

project@freebsd:~ % git clone https://
 
github.com/cesanta/elk.git
Cloning into 'elk'...
remote: Enumerating objects: 778, done.
remote: Counting objects: 100% (50/50), done.
remote: Compressing objects: 100% (33/33), done.
remote: Total 778 (delta 17), reused 17 (delta 17), pack-reused 728
Receiving objects: 100% (778/778), 4.27 MiB | 2.29 MiB/s, done.
Resolving deltas: 100% (364/364), done.

測試

cd elk/test
#檢視Makefile
 vim Makefile
CFLAGS ?= -W -Wall -Werror -Wno-deprecated -I.. -g -fsanitize=address,undefined -coverage -lm $(EXTRA)
CWD ?= $(realpath $(CURDIR))
ROOT ?= $(realpath $(CURDIR)/..)
DOCKER = docker run $(DA) --rm -e WINEDEBUG=-all -v $(ROOT):$(ROOT) -w $(CWD)
DESTDIR ?= .

define clean
  rm -rf  *.o *.dSYM ut* elk fuzzer* *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb slow-unit* _CL_* infer-out data.txt crash-* a.out tmp
endef

# %(call build,ENVIRONMENT,COMPILE,FLAGS,OUTPUT,RUN)
define build
  $(call clean)
  $1 $2 unit_test.c $3
  $1 $4
endef

all: test test++ vc2017 linux mingw elk

test:
        $(call build,,$(CC),$(CFLAGS) -o ut,$(RUN) ./ut)

test++:
        $(call build,,$(CXX),$(CFLAGS) -Wno-deprecated -o ut,./ut)

vc2017:
        $(call build,$(DOCKER) mdashnet/vc2017 wine64,cl,/nologo /W3 /O2 /I. $(EXTRA) /Feut.exe,ut.exe)

linux:
        $(call build,$(DOCKER) mdashnet/cc2,$(CC), $(CFLAGS) -o ut,./ut)

mingw:
        $(call build,$(DOCKER) mdashnet/mingw,i686-w64-mingw32-gcc,-W -Wall $(EXTRA) -o ut,wine ut)

arduino:
        curl -s http://downloads.arduino.cc/arduino-1.8.13-linux64.tar.xz -o /tmp/a.tgz
        tar -xf /tmp/a.tgz
        mv arduino-* $@

uno: arduino
        rm -rf tmp; mkdir tmp; cp ../examples/BlinkyJS/BlinkyJS.ino tmp/tmp.ino
        cp ../elk.c ../elk.h tmp/
        $(DOCKER) mdashnet/cc2 ./arduino/arduino --verify --board arduino:avr:nano tmp/tmp.ino

elk:
        $(CC) ../elk.c ../examples/cmdline/main.c -I.. -W -Wall -O2 -lm -o $(DESTDIR)/$@


coverage: test
        gcov -l -n *.gcno | sed '/^$$/d' | sed 'N;s/\n/ /'
        @gcov test.gcno >/dev/null

upload-coverage: coverage
        curl -s https://codecov.io/bash | /bin/bash

clean:
        $(call clean)

測試

gmake elk
project@freebsd:~/elk/test % ./elk -e "print('Hello World from ELk')"
Hello World from ELkundefined

project@freebsd:~/elk/test % gmake test
rm -rf  *.o *.dSYM ut* elk fuzzer* *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb slow-unit* _CL_* infer-out data.txt crash-* a.out tmp
cc unit_test.c -W -Wall -Werror -Wno-deprecated -I.. -g -fsanitize=address,undefined -coverage -lm  -o ut
./ut
FUNC: 14 [(n){return n<2?1:n*f(n-1);}]
FUNC: 14 [(){let n=0; while (n++ < 100){prnt(str(0,n)+'\n');} return n;}]
FUNC: 8 [(){}]
FUNC: 14 [(){}]
FUNC: 8 [(a,b){}]
FUNC: 12 [(a){return 17;}]
FUNC: 9 [(){}]
FUNC: 9 [(){}]
FUNC: 9 [(){1}]
FUNC: 9 [(){1;}]
FUNC: 9 [(){return 1;}]
FUNC: 9 [(){return 1;}]
FUNC: 9 [(){return 1;}]
FUNC: 9 [(){return 1;2;}]
FUNC: 9 [(){return 1;2;return 3;}]
FUNC: 9 [(a,b){return a + b;}]
FUNC: 9 [(a,b){return a + b;}]
FUNC: 9 [(a,b){return a + b;}]
FUNC: 9 [(a,b){return a + b;}]
FUNC: 12 [(a,b){return a + b;}]
FUNC: 20 [(){a++;}]
FUNC: 14 [(){ a++; }]
FUNC: 14 [(x){a=x;}]
FUNC: 14 [(x){a=x;}]
FUNC: 13 [(x){let z=x;a=typeof z}]
FUNC: 9 [(x){return x;}]
FUNC: 9 [(x){return {a:x};null;}]
FUNC: 9 [(x){let m= {a:7}; return m;}]
FUNC: 9 [(x){let m=7;return m;}]
FUNC: 9 [(x){let m='hi';return m;}]
FUNC: 9 [(x){let m={a:2};return m;}]
FUNC: 9 [(x){let m={a:x};return m;}]
FUNC: 16 [(x,y){return x*y;}]
FUNC: 10 [(){return 1;}]
FUNC: 11 [(x){return x+1;}]
FUNC: 14 [(x){return x;}]
FUNC: 8 [(x){return x;}]
FUNC: 14 [(x){return x*x;}]
FUNC: 8 [(x){return x*x;}]
FUNC: 16 [(){return 1;}]
FUNC: 14 [(x){return os.sum1(x,1);}]
FUNC: 8 [(x){return os.sum1(x,1);}]
FUNC: 14 [(x){return os.sum1(x,os.sum1(1,2));}]
FUNC: 8 [(x){return os.sum1(x,os.sum1(1,2));}]
FUNC: 10 [(x){return eval(null,x,x.length);}]
FUNC: 15 [(x){  let g = 'axds', h= 'sadlkasd', foo = {f:x};  a = foo.f; }]
FUNC: 8 [(x){  let g = 'axds', h= 'sadlkasd', foo = {f:x};  a = foo.f; }]
SUCCESS. All tests passed in 1078.12 ms