During our compiler's intermediate code generation phase, and more specifically while testing the arithmetic expressions and assignment rules, I noticed that although the respective quads are constructed successfully, when printing them out sometimes we'll get a bad_alloc exception. After tracing it, it looks like it's cause by the printQuads() method and specifically the following string access of key:
if(q.result != nullptr && q.result->sym != nullptr) {
cout << "quad " << opcodeStrings[q.op] << " inside if key check for" << opcodeStrings[q.op] << endl;
resultKey = q.result->sym->key;
}
I'll try to include the code that's relevant instead of dumping 500 lines of code here.
So, below you can see our assignmentexpr and basic arithmetic expression rules and actions:
expr: assignexpr
| expr PLUS expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in addition!" : "Second operand isn\'t a number in addition!";
yyerror(token_node, "Both addition operands must be numbers!");
} else
{
double result = $1->numConst + $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(add, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr MIN expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both suctraction operands must be numbers!");
} else
{
double result = $1->numConst - $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(sub, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr MUL expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both multiplication operands must be numbers!");
} else
{
double result = $1->numConst * $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(mul, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr DIV expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both division operands must be numbers!");
} else
{
if($3->numConst == 0) {
yyerror(token_node, "division by 0!");
} else {
double result = $1->numConst / $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(div_op, $1, $3, $$, nextquadlabel(), yylineno);
}
}
}
| expr MOD expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both modulus operands must be numbers!");
} else
{
if($3->numConst == 0) {
yyerror(token_node, "division by 0!");
} else {
double result = fmod($1->numConst,$3->numConst);
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(mod_op, $1, $3, $$, nextquadlabel(), yylineno);
}
}
}
...
assignexpr: lvalue ASSIGN expr { if ( isMemberOfFunc )
{
isMemberOfFunc=false;
}
else{ if ( islocalid==true ){
islocalid = false;
}else{
if ( isLibFunc($1->sym->key) ) yyerror(token_node,"Library function \"" + $1->sym->key + "\" is not lvalue!");
if (SymTable_lookup(symtab,$1->sym->key,scope,false) && isFunc($1->sym->key,scope)) yyerror(token_node,"User function \"" + $1->sym->key + "\" is not lvalue!");
}
}
if($1->type == tableitem_e)
{
// lvalue[index] = expr
emit(tablesetelem,$1->index,$3,$1,nextquadlabel(),yylineno);
$$ = emit_iftableitem($1,nextquadlabel(),yylineno, scope);
$$->type = assignment;
} else
{
emit(assign,$3,NULL,$1,nextquadlabel(),yylineno); //lval = expr;
$$ = newexpr(assignment);
$$->sym = newtemp(scope);
emit(assign, $1,NULL,$$,nextquadlabel(),yylineno);
}
}
;
The printQuads method is the following:
void printQuads() {
unsigned int index = 1;
cout << "quad#\t\topcode\t\tresult\t\targ1\t\targ2\t\tlabel" <<endl;
cout << "-------------------------------------------------------------------------------------------------" << endl;
for(quad q : quads) {
string arg1_type = "";
string arg2_type = "";
cout << "quad before arg1 type check" << endl;
if(q.arg1 != nullptr) {
switch (q.arg1->type) {
case const_bool:
arg1_type = "\'" + BoolToString(q.arg1->boolConst) + "\'";
break;
case const_string:
arg1_type = "\"" + q.arg1->strConst + "\"";
break;
case const_num:
arg1_type = to_string(q.arg1->numConst);
break;
case var:
arg1_type = q.arg1->sym->key;
break;
case nil_e:
arg1_type = "nil";
break;
default:
arg1_type = q.arg1->sym->key;
break;
}
}
cout << "quad before arg2 type check" << endl;
if(q.arg2 != nullptr) {
switch (q.arg2->type) {
case const_bool:
arg2_type = "\'" + BoolToString(q.arg2->boolConst) + "\'";
break;
case const_string:
arg2_type = "\"" + q.arg2->strConst + "\"";
break;
case const_num:
arg2_type = to_string(q.arg2->numConst);
break;
case nil_e:
arg2_type = "nil";
break;
default:
arg2_type = q.arg2->sym->key;
break;
}
}
string label = "";
if(q.op == if_eq || q.op == if_noteq || q.op == if_lesseq || q.op == if_greatereq
|| q.op == if_less || q.op == if_greater || q.op == jump) label = q.label;
string resultKey = "";
cout << "quad before key check" << endl;
if(q.result != nullptr && q.result->sym != nullptr) {
cout << "quad " << opcodeStrings[q.op] << " inside if key check for" << opcodeStrings[q.op] << endl;
resultKey = q.result->sym->key;
}
cout << "quad after key check" << endl;
cout << index << ":\t\t" << opcodeStrings[q.op] << "\t\t" << resultKey << "\t\t" << arg1_type << "\t\t" << arg2_type << "\t\t" << label << "\t\t" << endl;
index++;
}
}
The quads variable is just a vector of quads. Here is the quad struct:
enum expr_t {
var,
tableitem_e,
user_func,
lib_func,
arithmetic_e,
assignment,
newtable_e,
const_num,
const_bool,
const_string,
nil_e,
bool_e
};
struct expr {
expr_t type;
binding* sym;
expr* index;
double numConst;
string strConst;
bool boolConst;
expr* next;
};
struct quad {
iopcode op;
expr* result;
expr* arg1;
expr* arg2;
unsigned int label;
unsigned int line;
};
The binding* is defined as follows and is a symbol table binding:
enum SymbolType{GLOBAL_, LOCAL_, FORMAL_, USERFUNC_, LIBFUNC_, TEMP};
struct binding{
std::string key;
bool isactive = true;
SymbolType sym;
//vector<binding *> formals;
scope_space space;
unsigned int offset;
unsigned int scope;
int line;
};
Here are the emit(), newtemp & newexpr() methods:
void emit(
iopcode op,
expr* arg1,
expr* arg2,
expr* result,
unsigned int label,
unsigned int line
){
quad p;
p.op = op;
p.arg1 = arg1;
p.arg2 = arg2;
p.result = result;
p.label = label;
p.line = line;
currQuad++;
quads.push_back(p);
}
binding *newtemp(unsigned int scope){
string name = newTempName();
binding* sym = SymTable_get(symtab,name,scope);
if (sym== nullptr){
SymTable_put(symtab,name,scope,TEMP,-1);
binding* sym = SymTable_get(symtab,name,scope);
return sym;
}else return sym;
}
string newTempName(){
string temp = "_t" + to_string(countertemp) + " ";
countertemp++;
return temp;
}
expr* newexpr(expr_t exprt){
expr* current = new expr;
current->sym = NULL;
current->index = NULL;
current->numConst = 0;
current->strConst = "";
current->boolConst = false;
current->next = NULL;
current->type = exprt;
return current;
}
unsigned int countertemp = 0;
unsigned int currQuad = 0;
Symbol table cpp file:
#include <algorithm>
bool isHidingBindings = false;
/* Return a hash code for pcKey.*/
static unsigned int SymTable_hash(string pcKey){
size_t ui;
unsigned int uiHash = 0U;
for (ui = 0U; pcKey[ui] != '\0'; ui++)
uiHash = uiHash * HASH_MULTIPLIER + pcKey[ui];
return (uiHash % DEFAULT_SIZE);
}
/*If b contains a binding with key pcKey, returns 1.Otherwise 0.
It is a checked runtime error for oSymTable and pcKey to be NULL.*/
int Bucket_contains(scope_bucket b, string pcKey){
vector<binding> current = b.entries[SymTable_hash(pcKey)]; /*find the entry binding based on the argument pcKey*/
for (int i=0; i<current.size(); i++){
binding cur = current.at(i);
if (cur.key==pcKey) return 1;
}
return 0;
}
/*epistrefei to index gia to bucket pou antistixei sto scope 'scope'.Se periptwsh pou den uparxei
akoma bucket gia to en logw scope, ean to create einai true dhmiourgei to antistoixo bucket sto
oSymTable kai epistrefei to index tou.Diaforetika epistrefei thn timh -1.*/
int indexofscope(SymTable_T &oSymTable, unsigned int scope, bool create){
int index=-1;
for(int i=0; i<oSymTable.buckets.size(); i++) if (oSymTable.buckets[i].scope == scope) index=i;
if ( index==-1 && create ){
scope_bucket newbucket;
newbucket.scope = scope;
oSymTable.buckets.push_back(newbucket);
index = oSymTable.buckets.size()-1;
}
return index;
}
/*If there is no binding with key : pcKey in oSymTable, puts a new binding with
this key and value : pvvValue returning 1.Otherise, it just returns 0.
It is a checked runtime error for oSymTable and pcKey to be NULL.*/
int SymTable_put(SymTable_T &oSymTable, string pcKey,unsigned int scope, SymbolType st, unsigned int line){
int index = indexofscope(oSymTable,scope, true);
if(index==-1) cerr<<"ERROR"<<endl;
scope_bucket *current = &oSymTable.buckets.at(index);
if ( Bucket_contains(*current, pcKey) && st != FORMAL_ && st != LOCAL_) return 0; /*If the binding exists in oSymTable return 0.*/
binding newnode;
newnode.key = pcKey;
newnode.isactive = true;
newnode.line = line;
newnode.sym = st;
newnode.scope = scope;
current->entries[SymTable_hash(pcKey)].push_back(newnode);
return 1;
}
/*Pairnei ws orisma to oSymTable kai to scope pou theloume na apenergopoihsoume.
An to sugkekrimeno scope den uparxei sto oSymTable epistrefei -1.Diaforetika 0*/
void SymTable_hide(SymTable_T &oSymTable, unsigned int scope){
isHidingBindings = true;
for(int i=scope; i >= 0; i--) {
if(i == 0) return;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket *current = &oSymTable.buckets.at(index);
for (int i=0; i<DEFAULT_SIZE; i++) {
for (int j=0; j<current->entries[i].size(); j++) {
if(current->entries[i].at(j).sym == LOCAL_ || current->entries[i].at(j).sym == FORMAL_)
current->entries[i].at(j).isactive = false;
}
}
}
}
void SymTable_show(SymTable_T &oSymTable, unsigned int scope){
isHidingBindings = false;
for(int i=scope; i >= 0; i--) {
if(i == 0) return;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket *current = &oSymTable.buckets.at(index);
for (int i=0; i<DEFAULT_SIZE; i++) {
for (int j=0; j<current->entries[i].size(); j++) {
if(current->entries[i].at(j).sym == LOCAL_ || current->entries[i].at(j).sym == FORMAL_)
current->entries[i].at(j).isactive = true;
}
}
}
}
bool SymTable_lookup(SymTable_T oSymTable, string pcKey, unsigned int scope, bool searchInScopeOnly){
for(int i=scope; i >= 0; i--) {
if(searchInScopeOnly && i != scope) break;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket current = oSymTable.buckets[index];
for(vector<binding> entry : current.entries) {
for(binding b : entry) {
if(b.key == pcKey && b.isactive) return true;
else if(b.key == pcKey && !b.isactive) return false;
}
}
}
return false;
}
binding* SymTable_lookupAndGet(SymTable_T &oSymTable, string pcKey, unsigned int scope) noexcept{
for ( int i=scope; i >= 0; --i ){
int index = indexofscope(oSymTable,i,false );
if (index==-1) continue;
scope_bucket ¤t = oSymTable.buckets[index];
for (auto &entry : current.entries) {
for (auto &b : entry ){
if ( b.key == pcKey ) return &b;
}
}
}
return nullptr;
}
/*Lamvanei ws orisma to oSymTable, kleidh tou tou desmou pou psaxnoume kai to scope tou desmou.
H sunarthsh telika epistrefei to value tou tou desmou.Diaforetika epistrefei 0*/
binding* SymTable_get(SymTable_T &oSymTable, const string pcKey, unsigned int scope){
for ( int i=scope; i >= 0; --i )
{
const int index = indexofscope( oSymTable, i, false );
if ( index == -1 )
{
continue;
}
scope_bucket& current = oSymTable.buckets[index];
for ( auto& entry : current.entries)
{
for ( auto& b : entry )
{
if ( b.key == pcKey )
{
return &b;
}
}
}
}
return nullptr;
}
When run with the following test file, the issue occurs at the z5 = 4 / 2; expression's assign quad:
// simple arithmetic operations
z1 = 1 + 2;
z10 = 1 + 1;
z2 = 1 - 3;
z3 = 4 * 4;
z4 = 5 / 2;
What's confusing is that if I print out the sym->key after each emit() in the arithmetic-related actions, I can see the keys just fine. But once I try to access them inside the printQuads it will fail (for the div operation at least so far). This has me thinking that maybe we are shallow copying the binding* sym thus losing the key? But how come the rest of them are printed normally?
I'm thinking that the issue (which has occured again in the past at various stages) could be caused by us using a ton of copy-by-value instead of by-reference but I can't exactly confirm this because most of the time it works (I'm guessing that means that this is undefined behavior?).
I'm sure this is very difficult to help debug but maybe someone will eyeball something that I can't see after this many hours.
Debugging by eyeballing your code is probably a useful skill, but it's far from the most productive form of debugging. These days, it's much less necessary, since there are lots of good tools which you can use to detect problems. (Here, I do mean "you", specifically. I can't use any of those tools because I don't have your complete project in front of me. And nor do I particularly want it; this is not a request for you to paste hundreds of lines of code).
You're almost certainly right that your problem is related to some kind of undefined behaviour. If you're correct about the bad_alloc exception being thrown by what is effectively a copy of a std::string, then it's most likely the result of the thing being copied from not being a valid std::string. Perhaps it's an actual std::string object whose internal members have been corrupted; perhaps the pointer is not actually pointing to an active std::string (which I think is the real problem, see below). Or perhaps it's something else.
Either way, the error occurred long before the bug manifests itself, so you're only going to stumble upon where it happened by blind luck. On the other hand, there are a variety of memory error detection tools available which may be able to pinpoint the precise moment in which you violated the contract by reading or writing to memory which didn't belong to you. These include Valgrind and AddressSanitizer (also known as ASan); one or both of these is certainly available for the platform on which you are developing your project. (I say that confidently even without knowing what that platform is, but you'll have to do a little research to find the one which works best for your particular environment. Both of those names can be looked up on Wikipedia.) These tools are very easy to use, and extraordinarily useful; they can save you hours or days of debugging and a lot of frustration. As an extra added bonus, they can detect bugs you don't even know you have, saving you the embarrassment of shipping a program which will blow up in the hands of the customer or the person who is marking your assignment. So I strongly recommend learning how to use them.
I probably should leave it at that, because it's better motivation to learn to use the tools. Still, I can't resist making a guess about where the problem lies. But honestly, you will learn a lot more by ignoring what I'm about to say and trying to figure out the problem yourself.
Anyway, you don't include much in the way of information about your SymTable_T class, and the inconsistent naming convention makes me wonder if you even wrote its code; perhaps it was part of the skeleton code you were given for this assignment. From what I can see in SymTable_put and SymTable_get, the SymTable_T includes something like a hash table, but doesn't use the C++ standard library associative containers. (That's a mistake from the beginning, IMHO. This assignment is about learning how to generate code, not how to write a good hash table. The C++ standard library associative containers are certainly adequate for your purposes, whether or not they are the absolute ideal for your use case, and they have the enormous advantages of already being thoroughly documented and debugged.)
It's possible that SymTable_T was not originally written in C++ at all. The use of free-standing functions like SymTable_put and SymTable_get rather than class methods is difficult to explain unless the functions were originally written in C, which doesn't allow object methods. On the other hand, they appear to use C++ standard library collections, as evidenced by the call to push_back in SymTable_put:
current->entries[SymTable_hash(pcKey)].push_back(newnode);
That suggests that entries is a std::vector (although there are other possibilities), and if it is, it should raise a red flag when you combine it with this, from SymTable_get (whitespace-edited to save screen space here):
for ( auto& entry : current.entries) {
for ( auto& b : entry ) {
if ( b.key == pcKey )
return &b;
}
}
To be honest, I don't understand that double loop. To start with, you seem to be ignoring the fact that there is a hash table somewhere in that data structure, but beyond that, it seems to me that entry should be a binding (that's what SymTable_put pushes onto the entries container), and I don't see where a binding is an iterable object. Perhaps I'm not reading that correctly.)
Regardless, evidently SymTable_get is returning a reference to something which is stored in a container, probably a std::vector, and that container is modified from time to time by having new elements pushed onto it. And pushing a new element onto the end of a std::vector invalidates all existing references to every element of the vector. (See https://en.cppreference.com/w/cpp/container/vector/push_back)
Thus, newtemp, which returns a binding* acquired from SymTable_get, is returning a pointer which may be invalidated in the future by some call to SymTable_put (though not by every call to that function; only the ones where the stars unline unhappily). That pointer is then stored into a data object which will (much later) be given to printQuads, which will attempt to use the pointer to make a copy of a string which it will attempt to print. And, as I mentioned towards the beginning of this treatise, trying to use an object which is pointed to by a dangling pointer is Undefined Behaviour.
As a minor note, making a copy of a string in order to print it out is completely unnecessary. A reference would work just fine, and save a bunch of unnecessary memory allocations. But that won't fix the problem (if my guess turns out to be correct) because printing through a dangling pointer is just as Undefined Behaviour as making a copy through a dangling pointer, and will likely manifest in some other mysterious way.
I am working on an assignment in which we must create a 20-questions type game from a binary search tree. We read the tree in from a text file that is formatted like this:
Does it walk on 4 legs?
Does it fly?
*centipede?
Is it an insect?
*bird?
*butterfly?
Does it purr?
Does it howl?
*mouse?
*dog?
*cat?
Later, I am going to allow the user to add to this list. At the moment, however, I am unable to accurately read the list into a binary search tree. I have set it up so that (I think) it will use recursion and return to the previous "current" node pointer when it ends a loop of the function. Currently, however, the current node pointer remains the same.
The below function is passed a vector of the strings from the text file.
string line;
string guess;
bool start = true;
void buildTree(vector<string> gameData, Node* current, int &counter)
{
//fill node with question or answer
//recursive:
// add to the left until we encounter an asterisk
// add to the right
line = gameData[counter];
//if a question
if (line[0] != '*')
{
if (current->getData().empty())
{
current->setData(line);
cout << current->getData() << endl;
}
if (!start)
{
//if noChild is empty AND current isn't a guess, go to noChild
if ((current->getNo()->getData().empty())
&& (current->isGuess() == false))
{
current = current->getNo();
}
//otherwise, go to yes
else {
current = current->getYes();
}
}
while (counter < gameData.size())
{
if (!start) { counter++; }
start = false;
buildTree(gameData, current, counter);
}
}
//if a guess
else
{
//if data is full, go to no
if (current->getData().empty() == false)
{
current = current->getNo();
}
//otherwise, go to yes
else
{
//current = current->getYes();
for (int i = 1; i < line.size(); i++)
{
guess.push_back(line[i]);
}
current->setData(guess);
guess.clear();
cout << current->getData() << endl;
counter++;
current->setGuess(true);
}
}
}
It's the guy who was making the boggle simulator again! This time I have the issue of having a function that was forced to return a pointer to an object for syntax reasons. I want to access a function of the object that said pointer points to. How should I go about this? My code for the functions involved is below.
boggleNode * nextNode(int adj){
return adjacency[adj]; //For switching between nodes.
}
bool getUsed(){
return isUsed;
}
private:
boggleNode * adjacency[8];
char letter;
bool isUsed;
};
And finally, here is the function that contains the functions above:
int sift(boggleNode bog, string word, string matcher){
int endofnodes;
string matchee;
if (bog.getData() == 'q')
matchee = matcher + bog.getData() + 'u';
else
matchee = matcher + bog.getData();
if (compare(word, matcher) == 0){
cout << word << endl;
return 5; //If it finds the word, escape the loop.
}
if (word.find(matcher) == 0){
bog.makeUsed();
for (int j = 0; j < 8; j++){
if (bog.nextNode(j) != NULL){
if ((bog.nextNode(j)).getUsed() == 0){
endofnodes = sift(bog.nextNode(j), word, matchee);
if (endofnodes == 5)
return endofnodes;
}
}
bog.reset();
return 0;
//If it doesn't find anything, move onto next adjacency.
/*any words share a common starting letter sequence with matcher*/
//Sift using an adjacent node, and add the old string to the new one.
}
}
}
In which I am specifically asking about this line:
if ((bog.nextNode(j)).getUsed() == 0)
When I attempt to compile this code, I get " error: request for member
getUsed' in(&bog)->boggleNode::nextNode(j)', which is of non-class
type `boggleNode*' "
Any help is greatly appreciated. Thanks in advance!
You should use -> instead of .:
if ((bog.nextNode(j))->getUsed() == 0)
which is shorthand, in this case, for:
if ((*(bog.nextNode(j))).getUsed() == 0)
The incrementStock function calls the "addProduct" function only if the sku string given in the argument matches with a member of the "inventory" array (the array is of type *Product and of size 50). I initialized the array to nullptr in the constructor. "num" is the increment number.
When I test it and enter a valid sku to incrementStock, I get "no space" from the addproduct function.
void Supplier::addProduct(Product *p)
{
bool space = false;
int counter=0;
while(!space && counter < inventory.size() )
{
if(inventory[counter] == nullptr )
{
inventory[counter] = p;
space = true;
}
counter++;
}
if (!space)
{
cout << "no space" << endl;
}
}
void Supplier::incrementStock(const string &sku, int num)
{
bool found = false;
for( int i = 0; i < inventory.size(); i++ )
{
if( inventory[i] && sku == inventory[i]->getSKU())
{
found=true;
addProduct(inventory[i]);
inventory[i]->setQuantity(inventory[i]->getQuantity() +num);
}
}
if (found ==false)
{
cout << "not found" << endl;
}
}
Consider this loop:
for( int i = 0; i < inventory.size(); i++ )
If you get a match for sku within this loop, it will add an extra copy of that item into inventory. That's a bit odd, but fine if you want multiple copies of the same pointer in inventory.
The problem is that after that iteration of the loop, the loop will continue, and it will also find the copy we just made, and see that it matches, and then make another copy again. This repeats until the array is full.
I have had a similar issue with quite a few projects I have worked on involving classes containing arrays. I have a class that is supposed to handle a 2 dimensional matrix representing a TicTacToe game. There is an enumeration in the class for the status of the current game and one member function that has an enumeration return type. I cant seem to figure out why I can create the class set values in the matrix and as soon as I call the member function with the enumerated return type the whole array is reinitialized to 0. I think it has something to do with the constructor being called again or something along those lines but I have not been able to find anything after searching for the past few hours. Any help would be greatly appreciated.
Here is my header file containing the class information:
#ifndef TTT_H
#define TTT_H
#include <cstdlib>
#include <iostream>
using namespace std;
class TicTacToe
{
private:
enum Status{WinX, WinO, Continue, Draw};
int **board;
public:
TicTacToe();
~TicTacToe();
void PrintBoard();
bool ValidMove(int, int);
bool PlayerMove(int, int, int);
Status GameStatus(); //this one causes the problem
void Debug();
};
#endif
Here is the code for CPP file with the member function definitions:
#include "TicTacToe.h"
#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <cassert>
using namespace std;
TicTacToe::TicTacToe()
{
board = new int*[3];
assert(board != 0);
for(int i=0;i<3;i++)
{
cout << "Constructor Ran again" << endl; //for testing
board[i] = new int[3];
assert(board[i] != 0);
for(int j=0;j<3;j++)
board[i][j] = 9;
}
}
TicTacToe::TicTacToe(TicTacToe ©)
{
board = new int*[3];
assert(board != 0);
}
TicTacToe::~TicTacToe()
{
if(board)
delete[] board;
}
void TicTacToe::PrintBoard()
{
for(int i=0;i<3;++i)
{
for(int j=0;j<3;++j)
{
cout << "| ";
switch(board[i][j]){
case 0:
cout << "O ";
break;
case 1:
cout << "X ";
break;
case 9:
cout << " ";
break;
}
}
cout << "|" << endl;
cout << "------------" << endl;
}
}
bool TicTacToe::ValidMove(int row, int col)
{
bool valid = false;
if(row < 3 && col < 3)
{
if(board[row][col] == 9)
valid = true;
}
return valid;
}
bool TicTacToe::PlayerMove(int player, int row, int col)
{
bool done = false;
if(ValidMove(row,col) == true)
{
if(player == 1)
board[row][col] = 1;
else
board[row][col] = 0;
done = true;
}
return done;
}
TicTacToe::Status TicTacToe::GameStatus() //This function is the problem
{
int check, empty = 0;
bool done = false;
for(int i=0;i<3;++i)
{
for(int j=0;j<3;++j)
{
check += board[i][j];
if(board[i][j] = 9)
empty++;
}
if(check == 0)
return WinO;
else if(check == 3)
return WinX;
check = 0;
}
if(empty == 0)
return Draw;
for(int i=0;i<3;++i)
{
for(int j=0;j<3;++j)
check += board[j][i];
if(check == 0)
return WinO;
else if(check == 3)
return WinX;
check = 0;
}
check = board[0][0] + board[1][1] + board[2][2];
if(check == 0)
return WinO;
else if(check == 3)
return WinX;
check = 0;
check = board[0][2] + board[1][1] + board[2][0];
if(check == 0)
return WinO;
else if(check == 3)
return WinX;
check = 0;
return Continue;
}
void TicTacToe::Debug()
{
//cout << &board[0][0] << endl;
for(int i=0;i<3;++i)
{
for(int j=0;j<3;++j)
cout << board[i][j];
cout << endl;
}
}
Here is the driver file I am using to test:
#include "TicTacToe.h"
#include <iostream>
#include <cassert>
using namespace std;
int main()
{
int row, col;
bool valid;
enum Status{WinX, WinO, Continue, Draw};
TicTacToe * T;
T = new TicTacToe;
assert(T != 0);
cout << "There are 2 players. P1 is x P2 is o" << endl;
do
{
T->PrintBoard();
valid = false;
while(valid == false)
{
cout << "\nP1 choose a cell" ;
cin >> row >> col;
if(T->ValidMove(row, col) == true)
{
T->PlayerMove(1, row, col);
valid = true;
}
else
{
cout << "Not a valid choice" << endl;
valid = false;
}
}
T->PrintBoard();
cout << endl;
T->GameStatus(); //<<<<<this is the pain in my butt
T->PrintBoard();
valid = false;
while(valid == false)
{
cout << "\nP2 choose a cell" ;
cin >> row >> col;
if(T->ValidMove(row, col) == true)
{
T->PlayerMove(2, row, col);
valid = true;
}
else
{
cout << "Not a valid choice" << endl;
valid = false;
}
}
}
while(/*T->GameStatus() == Continue*/ 1==1);
//the call to GameStatus was commented out of the
//while statement for testing
return 0;
}
I know the code inside of the GameStatus function is far from pretty but the array is messed up before any of those lines are processed.
I left all of the other functions just to show that they work properly without issue.
Thanks in advance for any help you may be able to give.
You've got a simple typo in your code..
if(board[i][j] = 9) // will always return true (refp)
empty++;
Other remarks
When looking at your code a bit more thoroughly I see that you have a few other miss-happens, intentional or unintentional.. that I don't know:
int check is not initialized in TicTacToe::GameStatus
You are not freeing the allocated memory properly, you'll
need to free all entries in board, ie. delete board[i])
I don't like bugs, how can I get rid of the operator= vs operator== problem?
A quite common method to circumvent the problem of making a typo and writing = when you mean to compare (==) two variables is to flip the operands around (if one of them is a constant value, such as 9.
if(9 = board[i][j]) will not compile and such a bug would've never appeared in your code.
I'll have to say that I don't like writing my statements that way.. though it's a quite common method, especially in the "beginner" segment.
check is not initialized in GameStatus() .
if (board[i][j] = 9)
Isn't the above line of code resetting the array contents? You probably want to use == here, instead.
You have a serious issue in memory management. Look:
Your constructor performs 4 allocations (an array of pointers and 3 arrays of ints, to emulate a 2D arrray),
Your destructor performs 1 deallocation (= memory leak),
You have a custom destructor but you don't define (or block) operator= (you need to, see What is The Rule of Three?)
Your copy constructor is incomplete and doesn't create a "valid" object.
Basically the above is likely to cause you some memory problems. I suggest to:
Rewrite the destructor to first free all the arrays of ints, then the array of pointers,
Make the class TicTacToe uncopiable by declaring the copy constructor and the operator= as private.
Also some minor details on that matter:
board = new int*[3];
assert(board != 0);
The assertion is unnecessary. If the allocation fails, the operator new will throw an exception.
if(board)
delete[] board;
Operators delete and delete[] don't do anything if their argument is a null pointer, so that condition is redundant. Also you have designed your object with the invariant that the board exists as long as the TicTacToe object exists, so that check is totally unnecessary, right?
Keep it safe and simple!