Error in online playground

[mingodad]

This grammar nuke the online playground:
Console error message:

Uncaught (in promise) 5405224

Experimental Lua grammar:

chunk <-
	 SHEBANG? SKIP Block ! . #~{ synerr(yy, "unexpected syntax"); }

SHEBANG <-
	 '#!' ( ! LINEBREAK . )* LINEBREAK?

SKIP <-
	 ( SPACE+ / COMMENT )*

Block <-
	 ( Label / Return / Break / Goto / Do / While / Repeat / If / ForNum / ForIn / FuncDef / FuncDecl / VarDecl / Assign / call / ( ';' SKIP ) )*

Label <-
	 '::' NAME '::' SKIP

Return <-
	 'return' SKIP exprlist?

Break <-
	 'break' SKIP

Goto <-
	 'goto' SKIP NAME

Do <-
	 'do' SKIP Block 'end' SKIP

While <-
	 'while' SKIP expr 'do' SKIP Block 'end' SKIP

Repeat <-
	 'repeat' SKIP Block 'until' SKIP expr

If <-
	 'if' SKIP expr 'then' SKIP Block ( 'elseif' SKIP expr 'then' SKIP Block )* ( 'else' SKIP Block )? 'end' SKIP

ForNum <-
	 'for' SKIP Id '=' SKIP expr ',' SKIP expr ( ',' SKIP expr )? 'do' SKIP Block 'end' SKIP

ForIn <-
	 'for' SKIP idlist 'in' SKIP exprlist 'do' SKIP Block 'end' SKIP

FuncDef <-
	 'function' SKIP funcname funcbody

FuncDecl <-
	 'local' SKIP 'function' SKIP Id funcbody

VarDecl <-
	 'local' SKIP iddecllist ( '=' SKIP exprlist )?

Assign <-
	 varlist '=' SKIP exprlist

call <-
	 exprprimary ( ( indexsuffix+ callsuffix ) / callsuffix )+

NAME <-
	 ! KEYWORD ( NAME_PREFIX NAME_SUFFIX? ) SKIP

exprlist <-
	 expr ( ',' SKIP expr )*

expr <-
	 expror

Id <-
	 NAME

idlist <-
	 Id ( ',' SKIP Id )*

funcname <-
	 Id DotIndex* ColonIndex?

funcbody <-
	 '(' SKIP funcargs ')' SKIP Block 'end' SKIP

iddecllist <-
	 IdDecl ( ',' SKIP IdDecl )*

varlist <-
	 var ( ',' SKIP var )*

Number <-
	 NUMBER SKIP

NUMBER <-
	 HEX_NUMBER
	/ DEC_NUMBER

String <-
	 STRING SKIP

STRING <-
	 STRING_SHRT
	/ STRING_LONG

Boolean <-
	 ( 'false' SKIP )
	/ ( 'true' SKIP )

Nil <-
	 'nil' SKIP

Varargs <-
	 '...' SKIP

IdDecl <-
	 NAME ( '<' SKIP NAME '>' SKIP )?

Function <-
	 'function' SKIP funcbody

Table <-
	 '{' SKIP ( field ( fieldsep field )* fieldsep? )? '}' SKIP

field <-
	 Pair
	/ expr

fieldsep <-
	 ( ',' SKIP )
	/ ( ';' SKIP )

Paren <-
	 '(' SKIP expr ')' SKIP

Pair <-
	 ( '[' SKIP expr ']' SKIP '=' SKIP expr )
	/ ( NAME '=' SKIP expr )

Call <-
	 callargs

callargs <-
	 ( '(' SKIP ( expr ( ',' SKIP expr )* )? ')' SKIP )
	/ Table
	/ String

CallMethod <-
	 ':' SKIP NAME callargs

DotIndex <-
	 '.' SKIP NAME

ColonIndex <-
	 ':' SKIP NAME

KeyIndex <-
	 '[' SKIP expr ']' SKIP

indexsuffix <-
	 DotIndex
	/ KeyIndex

callsuffix <-
	 Call
	/ CallMethod

var <-
	 ( exprprimary ( ( callsuffix+ indexsuffix ) / indexsuffix )+ )
	/ Id

exprprimary <-
	 Id
	/ Paren

exprsuffixed <-
	 exprprimary ( indexsuffix / callsuffix )*

funcargs <-
	 ( ( Id ( ',' SKIP Id )* ( ',' SKIP Varargs )? ) / Varargs )?

opor <-
	 'or' SKIP exprand

exprand <-
	 exprcmp opand*

opand <-
	 'and' SKIP exprcmp

exprcmp <-
	 exprbor opcmp*

opcmp <-
	 ( ( '==' SKIP ) / ( '~=' SKIP ) / ( '<=' SKIP ) / ( '>=' SKIP ) / ( '<' SKIP ) / ( '>' SKIP ) ) exprbor

exprbor <-
	 exprbxor opbor*

opbor <-
	 '|' SKIP exprbxor

exprbxor <-
	 exprband opbxor*

opbxor <-
	 '~' SKIP exprband

exprband <-
	 exprbshift opband*

opband <-
	 '&' SKIP exprbshift

exprbshift <-
	 exprconcat opbshift*

opbshift <-
	 ( ( '<<' SKIP ) / ( '>>' SKIP ) ) exprconcat

exprconcat <-
	 exprarit opconcat*

opconcat <-
	 '..' SKIP exprconcat

oparit <-
	 ( ( '+' SKIP ) / ( '-' SKIP ) ) exprfact

exprfact <-
	 exprunary opfact*

opfact <-
	 ( ( '*' SKIP ) / ( '//' SKIP ) / ( '/' SKIP ) / ( '%' SKIP ) ) exprunary

exprunary <-
	 opunary
	/ exprpow

oppow <-
	 '^' SKIP exprunary

opunary <-
	 ( ( 'not' SKIP ) / ( '#' SKIP ) / ( '-' SKIP ) / ( '~' SKIP ) ) exprunary

expror <-
	 exprand opor*

exprarit <-
	 exprfact oparit*

exprpow <-
	 exprsimple oppow*

exprsimple <-
	 Nil
	/ Boolean
	/ Number
	/ String
	/ Varargs
	/ Function
	/ Table
	/ exprsuffixed

STRING_SHRT <-
	 $quote(["']) ( ESCAPE_SEQ / ( ! ( $quote / LINEBREAK ) . ) )* $quote

STRING_LONG <-
	 '[' $lsep('='*) '[' LINEBREAK? ( ! (']' $lsep ']') . )* ']' $lsep ']'

ESCAPE_SEQ <-
	 '\\' ESCAPE

LINEBREAK <-
	 '\r\n'
	/ '\n\r'
	/ '\n'
	/ '\r'

ESCAPE <-
	 [\'"]
	/ ( 'n' / 't' / 'r' / 'a' / 'b' / 'v' / 'f' )
	/ ( 'x' HEX_DIGIT HEX_DIGIT )
	/ ( 'u' '{' HEX_DIGIT HEX_DIGIT+ '}' )
	/ ( 'z' SPACE* )
	/ (DEC_DIGIT DEC_DIGIT !DEC_DIGIT / [012] DEC_DIGIT DEC_DIGIT)
	/ LINEBREAK

HEX_DIGIT <-
	 [0-9a-fA-F]

SPACE <-
	 ' '
	/ '\t'
	/ LINEBREAK

HEX_NUMBER <-
	 '0' [xX] HEX_PREFIX ( [pP] EXP_DIGITS )?

DEC_NUMBER <-
	 DEC_PREFIX ( [eE] EXP_DIGITS )?

HEX_PREFIX <-
	 ( HEX_DIGIT+ ( '.' HEX_DIGIT* )? )
	/ ( '.' HEX_DIGIT+ )

EXP_DIGITS <-
	 [+-]? DEC_DIGIT+

DEC_PREFIX <-
	 ( DEC_DIGIT+ ( '.' DEC_DIGIT* )? )
	/ ( '.' DEC_DIGIT+ )

DEC_DIGIT <-
	 [0-9]

COMMENT <-
	 '--' ( STRING_LONG / COMMENT_SHRT )

COMMENT_SHRT <-
	 ( ! LINEBREAK . )*

KEYWORD <-
	 ('and'
	/ 'break'
	/ 'do'
	/ 'elseif'
	/ 'else'
	/ 'end'
	/ 'false'
	/ 'for'
	/ 'function'
	/ 'goto'
	/ 'if'
	/ 'in'
	/ 'local'
	/ 'nil'
	/ 'not'
	/ 'or'
	/ 'repeat'
	/ 'return'
	/ 'then'
	/ 'true'
	/ 'until'
	/ 'while') !NAME_PREFIX

NAME_PREFIX <-
	 [_a-zA-Z]

NAME_SUFFIX <-
	 [_a-zA-Z0-9]+

EXTRA_TOKENS <-
	 '[[' '[=' '--'

[yhirose]

@mingodad, could you make it smaller which can still reproduce the problem? Thanks.

[mingodad]

sample.lua:

local lpeg = require 'lpeglabel'

On the command line:

./peglint lua.peglib sample.lua 
lua.peglib:346:1: 'EXTRA_TOKENS' is not referenced.
terminate called after throwing an instance of 'std::runtime_error'
  what():  Invalid back reference...
Aborted (core dumped)

With gdb:

gdb --args ./peglint lua.peglib sample.lua 
GNU gdb (Ubuntu 10.2-0ubuntu1~18.04~2) 10.2
...
(gdb) r
Starting program: /home/mingo/dev/c/A_grammars/cpp-peglib0/build/lint/peglint lua.peglib sample.lua
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
lua.peglib:346:1: 'EXTRA_TOKENS' is not referenced.
terminate called after throwing an instance of 'std::runtime_error'
  what():  Invalid back reference...

Program received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff71de7f1 in __GI_abort () at abort.c:79
#2  0x00007ffff7a630a9 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007ffff7a6e506 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007ffff7a6e571 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007ffff7a6e7f5 in __cxa_throw () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x0000555555570243 in peg::BackReference::parse_core (this=0x555555888020, 
    s=0x555555865f3d "require 'lpeglabel'.", n=19, vs=..., c=..., dt=std::any [no contained value])
    at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2814
#7  0x000055555556edf4 in peg::Ope::parse (this=0x555555888020, s=0x555555865f3d "require 'lpeglabel'.", n=19, 
    vs=..., c=..., dt=std::any [no contained value]) at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2626
#8  0x000055555556536a in peg::Sequence::parse_core (this=0x5555558886e0, s=0x555555865f3d "require 'lpeglabel'.", 
    n=19, vs=..., c=..., dt=std::any [no contained value])
    at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:1000
#9  0x000055555556edf4 in peg::Ope::parse (this=0x5555558886e0, s=0x555555865f3d "require 'lpeglabel'.", n=19, 
    vs=..., c=..., dt=std::any [no contained value]) at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2626
#10 0x000055555556f33f in peg::Holder::parse_core(char const*, unsigned long, peg::SemanticValues&, peg::Context&, std::any&) const::{lambda(std::any&)#1}::operator()(std::any&) const (__closure=0x7fffffff63f0, 
    a_val=std::any [no contained value]) at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2702
#11 0x000055555558f2b1 in peg::Context::packrat<peg::Holder::parse_core(char const*, unsigned long, peg::SemanticValues&, peg::Context&, std::any&) const::{lambda(std::any&)#1}>(char const*, unsigned long, unsigned long&, std::any&, peg::Holder::parse_core(char const*, unsigned long, peg::SemanticValues&, peg::Context&, std::any&) const::{lambda(std::any&)#1}) (this=0x7fffffffd170, a_s=0x555555865f3d "require 'lpeglabel'.", def_id=44, 
    len=@0x7fffffff6460: 93824995592520, val=std::any [no contained value], fn=...)
    at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:871
#12 0x000055555556f821 in peg::Holder::parse_core (this=0x555555888950, s=0x555555865f3d "require 'lpeglabel'.", 
    n=19, vs=..., c=..., dt=std::any [no contained value])
    at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2691
#13 0x000055555556edf4 in peg::Ope::parse (this=0x555555888950, s=0x555555865f3d "require 'lpeglabel'.", n=19, 
    vs=..., c=..., dt=std::any [no contained value]) at /home/mingo/dev/c/A_grammars/cpp-peglib0/lint/../peglib.h:2626

[mingodad]

And here is the minimal grammar that shows the problem:

STRING_SHRT <-
	 $quote(["']) ( !$quote . )* $quote

[yhirose]

@mingodad, thanks! I fixed the crash. cpp-peglib now reports undefined back reference errors.

> peglint lua.peg sample.lua
lua.peg:259:3: The back reference 'quote' is undefined.
lua.peg:259:37: The back reference 'quote' is undefined.
lua.peg:259:65: The back reference 'quote' is undefined.
lua.peg:262:7: The back reference 'lsep' is undefined.
lua.peg:262:43: The back reference 'lsep' is undefined.
lua.peg:262:63: The back reference 'lsep' is undefined.

Here is the correct grammar:

STRING_SHRT <-
	 $quote<["']> ( ESCAPE_SEQ / ( ! ( $quote / LINEBREAK ) . ) )* $quote

STRING_LONG <-
	 '[' $lsep<'='*> '[' LINEBREAK? ( ! (']' $lsep ']') . )* ']' $lsep ']'