C++ vector and segmentation faults
- by Headspin
I am working on a simple mathematical parser. Something that just reads number = 1 + 2;
I have a vector containing these tokens. They store a type and string value of the character. I am trying to step through the vector to build an AST of these tokens, and I keep getting segmentation faults, even when I am under the impression my code should prevent this from happening.
Here is the bit of code that builds the AST:
struct ASTGen
{
const vector<Token> &Tokens;
unsigned int size,
pointer;
ASTGen(const vector<Token> &t) : Tokens(t), pointer(0)
{
size = Tokens.size() - 1;
}
unsigned int next()
{
return pointer + 1;
}
Node* Statement()
{
if(next() <= size)
{
switch(Tokens[next()].type)
{
case EQUALS
:
Node* n = Assignment_Expr();
return n;
}
}
advance();
}
void advance()
{
if(next() <= size) ++pointer;
}
Node* Assignment_Expr()
{
Node* lnode = new Node(Tokens[pointer], NULL, NULL);
advance();
Node* n = new Node(Tokens[pointer], lnode, Expression());
return n;
}
Node* Expression()
{
if(next() <= size)
{
advance();
if(Tokens[next()].type == SEMICOLON)
{
Node* n = new Node(Tokens[pointer], NULL, NULL);
return n;
}
if(Tokens[next()].type == PLUS)
{
Node* lnode = new Node(Tokens[pointer], NULL, NULL);
advance();
Node* n = new Node(Tokens[pointer], lnode, Expression());
return n;
}
}
}
};
...
ASTGen AST(Tokens);
Node* Tree = AST.Statement();
cout << Tree->Right->Data.svalue << endl;
I can access Tree->Data.svalue and get the = Node's token info, so I know that node is getting spawned, and I can also get Tree->Left->Data.svalue and get the variable to the left of the =
I have re-written it many times trying out different methods for stepping through the vector, but I always get a segmentation fault when I try to access the = right node (which should be the + node)
Any help would be greatly appreciated.
