Syntax error in lex yacc -



Syntax error in lex yacc -

here lex yacc code parse xml file , print contents between , tags.

lex

%{ %} %% "<xml>" {return xmlstart;} "</xml>" {return xmlend;} [a-z]+ {yylval=strdup(yytext); homecoming text;} "<" {yylval=strdup(yytext);return yytext[0];} ">" {yylval=strdup(yytext);return yytext[0];} "\n" {yylval=strdup(yytext);return yytext[0];} . {} %%

yacc

%{ #include<stdio.h> #include<stdlib.h> #include<string.h> #define yystype char * %} %token xmlstart %token xmlend %token text %% programme : xmlstart '\n' '\n' xmlend {printf("%s",$3); } : '<' text '>' '\n' '\n' '<' text '>' { $$ = strcat($1,strcat($2,strcat($3,strcat($4,strcat($5,strcat($6,strcat($7,strcat($8,$9))))))));} | text %% #include"lex.yy.c"

i'm getting syntax error, tried using echos @ places didn't find error. input file i'm using is:

<xml> <hello> hi <hello> </xml>

please help me figure out error. have relatively less experience using lex , yacc

that grammar parse file has xmlend @ end. however, text files end newline.

although presumably prepare adding newline @ end of start rule, it's bad thought seek parse whitespace. in general, except line-oriented languages -- xml not -- best ignore whitespace.

your utilize of strcat incorrect. quoting man strcat gnu/linux system:

the strcat() function appends src string dest string, overwriting terminating null byte ('\0') @ end of dest, , adds terminating null byte. strings may not overlap, , the dest string must have plenty space result. if dest not big enough, programme behavior unpredictable; buffer overruns favorite avenue attacking secure programs.

you might want utilize asprintf if exists in standard library.

also, never free() strings produced strdup, of them leak memory. in general, it's improve not set strdup tokens string representation known -- particularly single-character tokens -- of import thing maintain track of tokens string value has been freshly allocated. apply semantic values produced asprintf if above suggestion taken.

yacc lex

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