c++ - Throw Exception in Bison and catch in main() -

is possibile throw exception in .y file , catch in .l yyparse() launched?

let's write example code. part of .y file:

%{ #include <stdio.h> #include <string> #include <cstring>  using namespace std;  extern int yylex(); extern void yyerror(char*);  typedef enum {  zero_division = 0,                 var_duplicate_name = 1,                 ...                 general = 100              } e_errors; const char* e_errnames[] = {"zero_division","var_duplicate_name",...,"general"}; ...  %}  //symbols %union {     ... };  %token ...  %start x1  %%  x1:     begin     ....     end     ;     {         ...          if(mycheck(i)>=0) throw var_duplicate_name;          ...     }     ; ...  %% 

and how i'm trying catch var_duplicate_name in wrong way in .l file:

%{ #include <string.h> #include "proxydata.tab.h"  void yyerror(char*); int yyparse(void);  char linebuf[500]; //for output row in case of syntax error  %}  %option yylineno  blanks          [ \t\n]+ text            [a-za-z0-9]+|[0-9]+.[0-9]+ %%  \n.*            { /* saving next row in case of syntax error */                   strncpy(linebuf, yytext+1, sizeof(linebuf)); /* save next line */                   yyless(1);      /* give \n rescan */                 }  {blanks}        { /* ignore */ };   ...             return(...);  {text}          { yylval.str_val=(char*)strdup(yytext);                   return(identifier);                 }  .               return yytext[0];  %%  void yyerror(char *s){      printf("line %d: %s @ %s in line:\n%s\n", yylineno, s, yytext, linebuf);     }  int yywrap (void){     ;     }  int main(int num_args, char** args){     if(num_args != 2) {printf("usage: ./parser filename\n"); exit(0);}     file* file = fopen(args[1],"r");     if(file == null) {printf("couldn't open %s\n",args[1]); exit(0);}     yyin = file;      try{     yyparse();     }catch(int err){         printf("error! %s",e_errnames[err]);     }      fclose(file); } 

in way, parser correctly created, when i'm giving in input file generates exception, face following message:

terminate called after throwing instance of 'e_errors' aborted (core dumped)

i know before writing printf("error! %s",e_errnames[err]), should declare. extern const char* e_errnames[]; enough on top of flex file?

you should call yyerror() or yy_abort designers intended. parsers shouldn't throw exceptions unless malfunction. , don't want 1 error parse, want them all.

nb you're not catching error in flex. you're catching in main(), can anywhere. yyparse() calls yylex(), not other way round. thrown yyparse() caught in main() or whatever else supply call it, not in yylex().