野牛：what（）：basic_string :: _ S_construct null无效

Question

So I'm using Bison for a project I'm working on. My bison file looks similar to this:

%{
#include <iostream>
....
%}
%union
{
  int intVal;
  double dVal;
  char charVal;
  char* strVal;
}
%token ID NUMBER INT DOUBLE CHAR STR END
%type <strVal> ID 
%type <strVal> INT DOUBLE CHAR STR END
%type <intVal> NUMBER
%type <strVal> dataType
%start program
%%
program: expressions
...
dataType: INT
        | DOUBLE
        | CHAR
        | STR
varDef: dataType ID { std::cout << $1 << endl; }
....

When i compile and run this and try running "int a" through it, it will print out $2 of varDef ("a") but when I tell it to print $1, i get

terminate called after throwing an instance of 'std::logic_error'
    what():  basic_string::_S_construct null not valid

I've also tried changing my %union to be

%union
{
   struct {
      ....
   };
}

and it didnt' change a thing. Any Idea what I'm doing wrong?

Answer 1

You have no actions for:

  dataType: INT
    | DOUBLE
    | CHAR
    | STR

The default action in bison is

{ $$ = $1 }

As the tokens

%token ID NUMBER INT DOUBLE CHAR STR END

Have no type you passed something with no value and no type to something which is type *char

(I see you now have solved it, but hopefully my explanation explains why)

Answer 2

If anyone's interested I just solved it. I changed

dataType: INT { $$ = "int"; }
        | DOUBLE { $$ = "double"; }
....

So i was actually passing in something null into cout. Thanks for the help!