Invoking a driver for parsing

In this recipe, you will learn how to call the parser function from the main function of our TOY parser.

How to do it…

To invoke a driver program to start parsing, define the driver function as shown in the following:

  1. Open the toy.cpp file:
    $ vi toy.cpp
  2. A Driver function called from the main function, and a parser can now be defined as follows:
    static void Driver() {
  while(1) {
    switch(Current_token) {
    case EOF_TOKEN : return;
    case ';' : next_token(); break;
    case DEF_TOKEN : HandleDefn(); break;
    default : HandleTopExpression(); break;
  }
  }
}
  3. The main() function to run the whole program can be defined as follows:
    int main(int argc, char* argv[]) {
  LLVMContext &Context = getGlobalContext();
  init_precedence();
  file = fopen(argv[1], "r");
  if(file == 0) {
    printf("Could not open file
");
  }
  next_token();
  Module_Ob = new Module("my compiler", Context);
  Driver();
  Module_Ob->dump();
      return 0;
}

How it works…

The main function is responsible for calling the lexer and parser so that both can act over a piece of code that is being input to the compiler frontend. From the main function, driver function is invoked to start the process of parsing.

See also

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