Local Symbol Table¶

Introduction¶

In addition to the global symbol table, the ExpL compiler maintains a separate local symbol table for each function for storing information regarding the arguments and local variables. Each function has its own list of local variables. So each function has its own Local Symbol Table.

Structure¶

struct Lsymbol{
    char *name;               //name of the variable
    struct Typetable *type;   //pointer to the Typetable entry of variable type
    int binding;              //stores memory address allocated to the variable
    struct Lsymbol *next;     //points to the next Local Symbol Table entry
};

Associated Methods¶

• struct Lsymbol* LInstall(char *name,struct Typetable *type): Creates a local symbol table with given 'name' and 'type' and also sets its 'binding'.
• struct Lsymbol* LLookup(char *name) : search the LST and if any entry with given 'name' is found ,return the entry,else returns NULL.

Memory is allocated for local variables of a function from a seperate memory area called the stack. Hence, the binding for a local variable is the relative address of the variable with respect to the base of the activation record for the function. A machine register called the base pointer points to the base of an activation record of a function. The binding is added to the base pointer to obtain the address of a variable in the stack.