What is expected?

Transcript

1. What is expected? ۚࢠ༤Ұ࿠(@yui-knk) 2019/12/14 ฏ੒Rubyձٞ01 Keynote

2. ࣗݾ঺հ • ۚࢠ ༤Ұ࿠ • Arm Treasure Data ॴଐ •

   Audience νʔϜ (RailsΞϓϦΛॻ͍͍ͯ·͢) • CRuby Committer 2015/12~ • GitHub (yui-knk)

3. 8F
   BSF
   IJSJOH https://www.treasuredata.com/company/careers/jobs/?team=Engineering

4. 8F
   BSF
   IJSJOH https://www.treasuredata.com/company/careers/jobs/?team=Engineering

5. What is expected?

6. What is expected? • ^^^ͷ෦෼ʹ͸ͲͷΑ͏ͳ” จࣈྻ”͕͸͍Δ͔ʁ def xxx ^^^

7. What is expected? • “m1”ͱ͍͏໊લͷϝιου Λఆٛ͢Δ def m1 end

8. What is expected? • “def”͕͘Δ͜ͱ΋͋Δ def def

9. What is expected? • “def”͕͘Δ͜ͱ΋͋Δ def def def def a;

   end

10. What is expected? $ ruby -wc -e 'def def a;

    end' Syntax OK

11. What is expected? • ໊લ͕”def"Ͱ1Ҿ਺"a"ΛͱΔϝιουΛఆ͍ٛͯ͠Δ • 2ͭ໨ͷ`def`͸`reswords`Ͱɺ͜Ε͸`fname`Ͱ`k_def fname ...` def

    def a ^^^ ^ | |-- args +------ method name end

12. What is expected? • ͋Δ࣌఺Ͱ࣍ʹདྷΔ͜ͱ͕Ͱ͖Δ”จࣈྻ” (expected tokens)ΛͲ͏΍ͬͯ஌Δ͜ͱ͕Ͱ͖Δͷ͔ʁ

13. How Ruby script is processed

14. How Ruby script is processed 4UFQ *OQVU 0VUQVU %FCVH 4PVSDF

    5PLFOJ[BUJPO 3VCZ
    TDSJQU 5PLFOT EVNQZ QBSTFZ
    1BSTJOH
    
    5PLFOT "45
    EVNQQ
    QBSTFZ
    $PNQJMF
    
    "45 #ZUF
    DPEF EVNQJ DPNQJMFD Parsing ___ \ Ruby script -> Tokens -> AST -> Byte code (insns / ISeq) __/ __/ Tokenization Compile

15. Ruby script 1 + 2

16. Tokenization Parsing ___ \ Ruby script -> Tokens -> AST

    -> Byte code (insns / ISeq) __/ __/ Tokenization Compile

17. Tokenization • Token͸ҎԼͷ2ͭͷ৘ใΛ΋ͭ • a token type (tINTEGER) • a

    semantic value (1) 1 + 2 ^ ^ ^^ | | |+--- '\n' / "end-of-input" | | +---- tINTEGER (2) | +------ '+' +-------- tINTEGER (1)

18. Tokenization $ ruby --dump=y -e '1 + 2' | grep

    Shifting Shifting token "integer literal" (1.0-1.1: 1) Shifting token '+' (1.2-1.3: ) Shifting token "integer literal" (1.4-1.5: 2) Shifting token '\n' (1.5-1.5: ) Shifting token "end-of-input" (1.5-1.5: ) On Ruby 2.7.0preview3

19. Parsing Parsing ___ \ Ruby script -> Tokens -> AST

    -> Byte code (insns / ISeq) __/ __/ Tokenization Compile

20. Parsing • Tokenྻ͕Rubyͷߏจʹ߹க͢Δ͔ΛνΣοΫ͢Δ • AST (Abstract Syntax Tree)Λߏங͢Δ

21. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y

22. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y W W W Rules

23. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y

24. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y 1 2.1 3r 4i

25. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y 1

26. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y 1

27. Parsing numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ;

    simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; %% program : { } top_compstmt parse.y Goal

28. Parsing $ ruby --dump=y -e '1 + 2' # Shifting

    token “integer literal” (1) “integer literal” simple_numeric numeric literal primary arg

29. Parsing # Shifting token '+' arg '+' # Shifting token

    “integer literal” (2) arg '+' “integer literal” arg '+' simple_numeric arg '+' numeric arg '+' literal arg '+' primary arg '+' arg arg expr stmt top_stmt top_stmts

30. Parsing # Shifting token '\n' top_stmts '\n' top_stmts term top_stmts

    terms top_stmts opt_terms top_compstmt program # Completed # Shifting token "end-of-input"

31. Build AST $ ruby --dump=p -e '1 + 2' NODE_SCOPE

    NODE_OPCALL (:+) NODE_LIT (1) NODE_LIST NODE_LIT (2) NODE_SCOPE NODE_OPCALL (:+) NODE_LIT (1) NODE_LIST NODE_LIT (2)

32. Compile Parsing ___ \ Ruby script -> Tokens -> AST

    -> Byte code (insns / ISeq) __/ __/ Tokenization Compile

33. Compile • ίϯύΠϧΛ͢Δ • See “compile.c” $ ruby --dump=i -e

    '1 + 2' == disasm: #<ISeq:<main>@-e:1 (1,0)-(1,5)> (catch: FALSE) 0000 putobject_INT2FIX_1_ ( 1)[Li] 0001 putobject 2 0003 opt_plus <calldata!mid:+, argc:1, ARGS_SIMPLE> 0005 leave

34. 1BSTFS
    JT
    UPEBZ`T
    UPQJD • expected tokens͸ߏจղੳ্ͷ໰୊ Parsing ___ \ Ruby script ->

    Tokens -> AST -> Byte code (insns / ISeq) __/ __/ Tokenization Compile

35. What is parser?

36. • ೖྗจࣈྻ͕จ๏͔ΒͲͷΑ͏ʹੜ੒Ͱ͖Δ͔Λܭࢉ͢ Δ͜ͱ • RubyͰ͸GNU BisonΛ͔ͭͬͯLALR(1)ύʔβΛੜ੒͢Δ • GNU Bison͸parse.yΛೖྗͱͯ͠ύʔβͷCίʔυΛ ग़ྗ͢Δ

    • ߏจղੳදΛͭͬͯ͘ϓογϡμ΢ϯΦʔτϚτϯΛར༻ ͯ͠ߏจΛղੳ͢Δ What is parser?

37. • ੜ੒نଇ (Production Rule): • ྫ) simple_numeric: tINTEGER • ͖͞΄ͲͷྫͰ͸programΛى఺ʹੜ੒نଇΛద༻ͯ͠

    ͍ͬͯ࡞Δ͜ͱͷͰ͖Δ΋ͷ͕ɺͦͷจ๏ʹΑͬͯఆ ٛ͞ΕΔݴޠͱͳΔ simple_numeric : tINTEGER | tFLOAT | tRATIONAL | tIMAGINARY ; 8IBU
    JT
    HSBNNBS

38. • ඇऴ୺ه߸ (Nonterminal): RuleͷࠨลʹදΕΔه߸ • ྫ) program, numeric, simple_numeric •

    ӈลʹ΋දΕΔ͜ͱ͕͋Δ • ऴ୺ه߸ (Terminal): Ruleͷӈลʹ͔͠දΕͳ͍ه߸ • ྫ) tINTEGER, tUMINUS_NUM, tLOWEST numeric : simple_numeric | tUMINUS_NUM simple_numeric %prec tLOWEST ; 8IBU
    JT
    HSBNNBS ऴ୺ه߸ ඇऴ୺ه߸

39. How parser works? L : L ';' E /* Rule

    1 */ | E /* Rule 2 */ ; E : E ',' P /* Rule 3 */ | P /* Rule 4 */ ; P : 'a' /* Rule 5 */ | '(' M ')' /* Rule 6 */ ; M : /* nothing */ /* Rule 7 */ | L /* Rule 8 */ ; a;()

40. • Shift: ࣍ͷtokenΛstackʹϓογϡ͢Δ • Reduce: ͋ΔϧʔϧΛ࢖ͬͯӈ͔ΒnݸͷtokenΛஔ͖׵͑Δ How parser works? "a"

    ";" "(" ")" $end # Shift "a" ";" "(" ")" $end # Reduce by rule 5 P ";" "(" ")" $end # Reduce by rule 4 E ";" "(" ")" $end # Reduce by rule 2 L ";" "(" ")" $end # Shift L ";" "(" ")" $end # Shift L ";" "(" ")" $end # Reduce by rule 7 L ";" "(" M ")" $end # Shift L ";" "(" M ")" $end # Reduce by rule 6 L ";" P $end # Reduce by rule 4 L ";" E $end # Reduce by rule 1 L $end # Shift L $end # accept Rule 6. P: (M) ʹΑΔreduce stack ೖྗτʔΫϯ

41. How parser works? • Shift/ReduceΛͦΕͧΕ͍ͭߦ͏΂͖͔ʁ • ߏจղੳදʹج͍ͮͯ൑அ͢Δ

42. -"-3 
    UBCMF • sN: Shiftͯ͠NΛstackʹpush • rN: ϧʔϧNͰReduce͢Δ •

    acc: डཧ • ۭന: ߏจΤϥʔ • GOTO: ඇऴ୺ه߸༻ɻNΛstack ʹpush https://www.cs.uic.edu/~spopuri/cparser.html#dragonbook-tables

43. )PX
    UP
    DSFBUF
    UIF
    UBCMF • Ruleͷӈลʹ ‘.’ ΛՃ͑ͨ΋ͷΛߟ͑Δ 1~4 • ‘.’ ͸ruleͷͲ͜·ͰಡΜ͔ͩΛ͋ΒΘ͢ •

    2Ͱ͋Ε͹࣍ʹ ‘;’ ͕͘Δ͜ͱΛظ଴͍ͯ͠ΔͷͰɺ ‘;’ ͳ Βshift͢Δ • 4ͳΒreduceͯ͠Lʹ͢Δ • ͜ΕΒΛLR(0)߲ͱ͍ͬͨΓ͢Δ 0 L: L ';' E 1 L: . L ';' E 2 L: L . ';' E 3 L: L ';' . E 4 L: L ';' E .

44. )PX
    UP
    DSFBUF
    UIF
    UBCMF • LALR(1)ͷ৔߹LR(1)߲Λ࢖͏ • LR(0)߲ʹ͞Βʹtoken 1ͭΛઌಡΈͨ͠΋ͷ L: E . /

    [$end, ';', ')']

45. )PX
    UP
    DSFBUF
    UIF
    UBCMF • 1ͷ৔߹ɺ࣍ʹظ଴͞ΕΔͷ͸E • E͸ผͷruleͰreduce͢Δ͜ͱʹΑͬͯൃੜ͢Δ͔΋͠Ε ͳ͍(3, 4) • P͸ผͷruleͰ… (5,

    6) • ‘a’ ΍ ‘(’ ͸ऴ୺ه߸ͳͷͰผͷrule͔Β͸ൃੜ͠ͳ͍ • ߲͸͍͔ͭ͘ͷάϧʔϓʹ෼͚ΒΕΔ 1 L: L ';' . E 3 E: . E ',' P 4 | . P 5 P: . 'a' 6 | . '(' M ')'

46. )PX
    UP
    DSFBUF
    UIF
    UBCMF

47. )PX
    UP
    DSFBUF
    UIF
    UBCMF ॳظঢ়ଶ डཧ

48. )PX
    UP
    DSFBUF
    UIF
    UBCMF PΛshift

49. )PX
    UP
    DSFBUF
    UIF
    UBCMF reduce

50. )PX
    UP
    DSFBUF
    UIF
    UBCMF shift΋͘͠͸reduce

51. )PX
    UP
    HFU
    FYQFDUFE
    UPLFOT • state 3ʹ͍ΔͳΒɺ‘;’ ‘,’ ‘)’ ‘$’͕expected tokensʹͳΔ https://www.cs.uic.edu/~spopuri/cparser.html#dragonbook-tables

52. Bison’s compressed table

53. 5BCMF
    JT
    TQBSTF • actionςʔϒϧ͸ 37/78 = 47% ͔͠ຒ·ͬͯͳ͍ • GOTOςʔϒϧ͸ 10/52

    = 19% ͔͠ຒ·ͬͯͳ͍ • Ruby 2.7.3 pre3Ͱ͸ 1234 state, 411 symbols https://www.cs.uic.edu/~spopuri/cparser.html#dragonbook-tables

54. Compress table (1) • Default Reductions, Default GOTOsʹΑΔѹॖ • actionςʔϒϧ͸ԣํ޲ɺ

    GOTOςʔϒϧ͸ॎํ޲ʹѹ ॖ • state 5 -> r3 • PͷGOTO -> 9 https://www.cs.uic.edu/~spopuri/cparser.html#dragonbook-tables

55. Compress table (2) • Default ReductionsΛಋೖͯ͠΋ɺ·ͩ sparse • double displacementʹΑΔѹॖ

    https://www.cs.uic.edu/~spopuri/cparser.html#table-compression ΛҰ෦मਖ਼

56. Compress table (2) • ࣮ࡍͷ஋Λ΋ͭyytable, guard tableͰ͋Δyycheck, offset Λ؅ཧ͢Δyypactͷ3ͭͰදݱ͢Δ 0:

    [ , , , , , 1, 2, ] 2: [ , , , , , 1, 2, ] 3: [ 8, , , 9, , , , ] 4: [ , , , , 10, , , ] 6: [ , , , 9, , , , ] 7: [ , , , , , , , 11] 9: [ , , , , , 1, 2, ] 10: [ , , , , , 1, 2, ] 12: [ , , , , 10, , , ] yycheck [0, 5, 6, 3, 7, 4, 3, 2, 9, -1, -1, -1, 10] yytable [8, 1, 2, 9, 11, 10, 9, 6, 12, 0, 0, 0, 13] yypact [-4, -5, -4, 0, 1, -5, 3, -3, -5, -4, -4, -5, 1, -5]

57. • state 0ͷέʔεΛߟ͑ͯΈΔ Compress table (2) 0: [ , ,

    , , , 1, 2, ] 2: [ , , , , , 1, 2, ] 3: [ 8, , , 9, , , , ] 4: [ , , , , 10, , , ] 6: [ , , , 9, , , , ] 7: [ , , , , , , , 11] 9: [ , , , , , 1, 2, ] 10: [ , , , , , 1, 2, ] 12: [ , , , , 10, , , ] yycheck [0, 5, 6, 3, 7, 4, 3, 2, 9, -1, -1, -1, 10] yytable [8, 1, 2, 9, 11, 10, 9, 6, 12, 0, 0, 0, 13] yypact [-4, -5, -4, 0, 1, -5, 3, -3, -5, -4, -4, -5, 1, -5] yypact[0] = -4

58. Compress table (2) index = 5 Ͱ͸yycheckͷ஋ͱҰக͢Δ 0: [ ,

    , , , , 1, 2, ] 2: [ , , , , , 1, 2, ] 3: [ 8, , , 9, , , , ] 4: [ , , , , 10, , , ] 6: [ , , , 9, , , , ] 7: [ , , , , , , , 11] 9: [ , , , , , 1, 2, ] 10: [ , , , , , 1, 2, ] 12: [ , , , , 10, , , ] yycheck [0, 5, 6, 3, 7, 4, 3, 2, 9, -1, -1, -1, 10] yytable [8, 1, 2, 9, 11, 10, 9, 6, 12, 0, 0, 0, 13] yypact [-4, -5, -4, 0, 1, -5, 3, -3, -5, -4, -4, -5, 1, -5]

59. Compress table (2) index = 5 ͷ஋͸ 1 (= yytable[1])

    0: [ , , , , , 1, 2, ] 2: [ , , , , , 1, 2, ] 3: [ 8, , , 9, , , , ] 4: [ , , , , 10, , , ] 6: [ , , , 9, , , , ] 7: [ , , , , , , , 11] 9: [ , , , , , 1, 2, ] 10: [ , , , , , 1, 2, ] 12: [ , , , , 10, , , ] yycheck [0, 5, 6, 3, 7, 4, 3, 2, 9, -1, -1, -1, 10] yytable [8, 1, 2, 9, 11, 10, 9, 6, 12, 0, 0, 0, 13] yypact [-4, -5, -4, 0, 1, -5, 3, -3, -5, -4, -4, -5, 1, -5]

60. DPNQSFTTFE
    UBCMFͷಛ௃ • double displacement • ෮ݩՄೳͳͷͰ໰୊ͳ͍ • default reductions •

    errorൃੜ͕஗Ԇͯ͠expected tokens͕มΘͬͯ͠·͏ • expected tokensͷܭࢉ͕ͦͷ࣌఺ͷstate stackʹґଘ ͢Δ

61. &SSPSൃੜͷ஗Ԇ • ҎԼͷྫ͸ຊ౰ʹ”when”͚ͩͳͷ͔ʁ $ ruby -e 'case a;' -e:1: syntax

    error, unexpected end-of-input, expecting `when'

62. &SSPSൃੜͷ஗Ԇ • “in”΋ॻ͘͜ͱ͕Ͱ͖Δ $ ruby -wce 'case a; in b;

    end' -e:1: warning: Pattern matching is experimental, and the behavior may change in future versions of Ruby! Syntax OK

63. &SSPSൃੜͷ஗Ԇ case a; ^ State 375 737 opt_terms: terms .

    ["`when'", "`in'"] ... $default reduce using rule 737 (opt_terms) State 587 ... $default reduce using rule 330 (@18) State 717 331 primary: k_case expr_value opt_terms @18 . case_body k_end 367 k_when: . "`when'" 464 case_body: . k_when case_args then compstmt cases "`when'" shift, and go to state 719 k_when go to state 720 case_body go to state 841 default reduceʹΑͬͯstate 717·ͰҠಈ͢Δ

64. 4UBDL΁ͷґଘ

65. 4UBDL΁ͷґଘ • ‘;’ ‘,’ ‘$end’͸ຊདྷͳΒerror • ຊདྷerror͔Ͳ͏͔Λ֬ೝ͢Δ ͨΊʹ࣮ࡍʹreduce͢Δඞཁ ͕͋Δ •

    ͜ͷܭࢉͷ݁Ռ͸ͦͷ࣌఺ͷ stackʹґଘ͢Δ • ςετͷෳࡶ͕͞૿͢ https://www.cs.uic.edu/~spopuri/cparser.html#modified-tables ΛҰ෦मਖ਼

66. 8PSLBSPVOE • lr.default-reduction Λ accepting ʹ͢Δ͜ͱͰdefault reduce͞ΕΔ෦෼ΛݮΒ͢͜ͱ͕Ͱ͖Δ • https://www.gnu.org/software/bison/manual/html_node/ Default-Reductions.html

67. 1JUGBMM
    PG
    UIF
    XPSLBSPVOE
    • ruby͕buildͰ͖ͳ͘ͳΔ • ຊདྷ͸tLABELͱ͍͏τʔΫϯʹͳΔ $ ./miniruby -v <internal:gc>:33: syntax

    error, unexpected ':' def self.start full_mark: true, immediate_mark: true, ...

68. • tLABELΛు͖ग़͢ʹ͸EXPR_LABEL|EXPR_ENDFN͕ඞ ཁ 1JUGBMM
    PG
    UIF
    XPSLBSPVOE
    #define IS_LABEL_POSSIBLE() (\ (IS_lex_state(EXPR_LABEL|EXPR_ENDFN) && !cmd_state)

    || \ IS_ARG()) static enum yytokentype parse_ident(struct parser_params *p, int c, int cmd_state) { ... if (IS_LABEL_POSSIBLE()) { if (IS_LABEL_SUFFIX(0)) { SET_LEX_STATE(EXPR_ARG|EXPR_LABELED); nextc(p); set_yylval_name(TOK_INTERN()); return tLABEL; } }

69. • fnameͷ࣍ͷΞΫγϣϯͰlex_stateΛηοτ͍ͯ͠Δ 1JUGBMM
    PG
    UIF
    XPSLBSPVOE
    | k_def singleton dot_or_colon {SET_LEX_STATE(EXPR_FNAME);} fname {

    $<num>4 = p->in_def; p->in_def = 1; SET_LEX_STATE(EXPR_ENDFN|EXPR_LABEL); /* force for args */ local_push(p, 0); $<id>$ = p->cur_arg; p->cur_arg = 0; } f_arglist

70. #FGPSF • ͱΓ͋͑ͣΞΫγϣϯ(@26)Λ࣮ߦ͢Δ State 858 346 @26: . %empty 347

    primary: k_def singleton dot_or_colon @25 fname . @26 f_arglist bodystmt k_end $default reduce using rule 346 (@26) @26 go to state 961

71. "GUFS • ΞΫγϣϯΛ࣮ߦ͢ΔલʹtLABELΛཁٻ͢ΔΑ͏ʹͳͬ ͨ State 858 346 @26: . %empty

    ["local variable or method", "global variable", "instance variable", "constant", "class variable", tLABEL, "**", "(", "*", "**arg", "&", '&', '*', '(', ';', '\n'] 347 primary: k_def singleton dot_or_colon @25 fname . @26 f_arglist bodystmt k_end "local variable or method" reduce using rule 346 (@26) ... tLABEL reduce using rule 346 (@26) ... @26 go to state 961

72. Current implementation

73. static enum yytokentype -yylex(YYSTYPE *lval, YYLTYPE *yylloc, struct parser_params *p)

    +yylex(YYSTYPE *lval, YYLTYPE *yylloc, struct parser_params *p, int yystate, short *yyss, short *yyssp) { enum yytokentype t; + VALUE yysstack; p->lval = lval; lval->val = Qundef; + + yysstack = yysstack_new(yyss, yyssp); + + if (p->debug) { + VALUE tokens = expected_tokens(yystate, yysstack); + rb_parser_printf(p, "\nexpected_tokens (state = %d): %"PRIsVALUE"\n", yystate, tokens); + } + stackΛίϐʔ͢Δ stateͱstackΛҾ਺ʹ௥Ճ https://github.com/ruby/ruby/compare/master...yui-knk:feature/ expected_tokens_v2_7_0_preview3_heisei_01?expand=1

74. /* See also: yysyntax_error and yybackup */ static VALUE expected_tokens(const

    int yystate, VALUE yysstack) { VALUE ary = rb_ary_new(); for (int yytoken = 0; yytoken < YYNTOKENS; ++yytoken) { push_expected_token(ary, yystate, yytoken, rb_ary_dup(yysstack)); } return ary; } શtokenʹରͯ͠push_expected_tokenΛݺͼग़͢

75. static void push_expected_token(VALUE ary, const int yystate, const int yytoken,

    VALUE yysstack) { int yyn = yypact[yystate]; /* See: yydefault label */ if (yypact_value_is_default(yyn)) { int new_state; if ((new_state = default_reduce(yystate, yytoken, yysstack)) >= 0) { /* yysstack is changed */ push_expected_token(ary, new_state, yytoken, yysstack); } return; } default reduction ͷͱ͖ ࣮ࡍʹreduceͯࣗ͠਎Λ࠶ؼݺͼग़͠

76. yyn += yytoken; if (yyn < 0 || YYLAST <

    yyn || yycheck[yyn] != yytoken) { int new_state; if ((new_state = default_reduce(yystate, yytoken, yysstack)) >= 0) { /* yysstack is changed */ push_expected_token(ary, new_state, yytoken, yysstack); } return; } default reduction ͷͱ͖ ࣮ࡍʹreduceͯࣗ͠਎Λ࠶ؼݺͼग़͠

77. yyn = yytable[yyn]; if (yyn <= 0) { if (!yytable_value_is_error(yyn))

    { rb_ary_push(ary, rb_str_new2(yytname[yytoken])); return; } } else { rb_ary_push(ary, rb_str_new2(yytname[yytoken])); return; } } reduction ͷͱ͖ shift ͷͱ͖ expected tokensʹ௥Ճ͢Δ

78. $ ./miniruby --dump=y -e 'case a;' ... Entering state 375

    Reading a token: expected_tokens (state = 375): ["\"`when'\"", "\"`in'\"", "';'"] ... -e:1: syntax error, unexpected end-of-input, expecting `when' ...

79. • yypact΍yytableͳͲBisonͷ࣮૷ʹڧ͘ґଘ͢Δ࣮૷ʹ ͳ͍ͬͯΔ yyn += yytoken; if (yyn < 0

    || YYLAST < yyn || yycheck[yyn] != yytoken) { int new_state; if ((new_state = default_reduce(yystate, yytoken, yysstack)) >= 0) { /* yysstack is changed */ push_expected_token(ary, new_state, yytoken, yysstack); } return; }

80. • ੈͷதʹ͸ tool/ytab.sed ͷΑ͏ͳίʔυ΋͋Δ #!/bin/sed -f # This file is

    used when generating code for the Ruby parser. ... s/^yysyntax_error (/&struct parser_params *p, / s/ yysyntax_error (/&p, / s/\( YYFPRINTF *(\)yyoutput,/\1p,/ s/\( YYFPRINTF *(\)yyo,/\1p,/ s/\( YYFPRINTF *(\)stderr,/\1p,/ s/\( YYDPRINTF *((\)stderr,/\1p,/ s/^\([ ]*\)\(yyerror[ ]*([ ]*parser,\)/\1parser_\2/ s!^ *extern char \*getenv();!/* & */! s/^\(#.*\)".*\.tab\.c"/\1"parse.c"/ /^\(#.*\)".*\.y"/s:\\\\:/:g

81. 'VUVSF
    XPSL • ςετํ๏Λߟ͑Δඞཁ͕͋Δ • yyss, yysspʹґଘͨ͠ίʔυ͸SEGV͢ΔՄೳੑ͕͋Δͷ Ͱผͷํ๏Λߟ͑Δ

82. ·ͱΊ • expected tokens͸parserͷ৘ใ͔Βܾఆ͢Δ͜ͱ͕Ͱ͖ Δ • Default ReductionsΛ͏·͘ѻ͏ͷ͸೉͍͠ • ҰํͰRuby͸Default

    Reductionsͷڍಈʹґଘ͍ͯ͠Δͷ Ͱ͏·͘෇͖߹͍ͬͯ͘ඞཁ͕͋Δ

83. "DLOPXMFEHFNFOUT • @takeshinoda and @hkdnet • Reviewing the slide

84. ࢀߟจݙ • Rubyॲཧܥશൠ • http://i.loveruby.net/ja/rhg/book/ • "Rubyͷ͘͠ΈɹRuby Under a Microscope”

    • Parser • http://i.loveruby.net/ja/rhg/book/ • "ίϯύΠϥ―ݪཧɾٕ๏ɾπʔϧ (Information & Computing)” • Bison • https://www.cs.uic.edu/~spopuri/cparser.html

85. Thank you !!