我正在使用C ++。我正在研究一种更改堆栈的最大容量的方法,但我对收到的错误感到困惑。下面是我的方法。
void Stack::setCapacity(unsigned newCapacity){
if(newCapacity< this->getSize()){
throw StackException("setCapacity()",
"the size is larger than the desired capacity");
} else {
if(newCapacity != myCapacity){
Item * tempArray = new Item[newCapacity];
if(newCapacity < myCapacity){
for(unsigned i=0; i<newCapacity;i++){
tempArray[i] = myArray[i];
}
} else if (newCapacity > myCapacity) {
for(unsigned i=0; i<myCapacity; i++){
tempArray[i] = myArray[i];
}
}
for(unsigned i=0; i<newCapacity; i++){
myArray[i] = tempArray[i];
}
delete tempArray;
}
myCapacity = newCapacity;
}
}
我还编写了一个测试方法来测试我的setCapacity()方法是否有效。
void StackTester::setCapacityTest() {
cout << "- setCapacity... " << flush;
// empty stack
Stack st7(5);
assert(st7.getSize() == 0);
assert(st7.getCapacity() == 5);
st7.setCapacity(7);
assert(st7.getCapacity() == 7);
cout << " 1 " << flush;
// partially filled stack - larger capacity
Stack st8(5);
assert(st8.getCapacity() == 5);
st8.push(3);
st8.push(4);
st8.setCapacity(7);
assert(st8.getCapacity() == 7);
assert(st8.getTop() == 4);
st8.pop();
assert(st8.getTop() == 3);
cout << " 2 " << flush;
// size larger than new capacity
try{
Stack st9(3);
st9.push(7);
st9.push(4);
st9.push(11);
assert(st9.getSize() == 3);
st9.setCapacity(2);
cerr << "setCapacity's new capacity is larger than the size";
exit(1);
} catch(StackException& se){
cout << " 3 " << flush;
}
// partially filled stack - smaller capacity
Stack st10(5);
assert(st10.getCapacity() == 5);
st10.push(1);
st10.setCapacity(2);
assert(st10.getCapacity() == 2);
assert(st10.getTop() == 1);
cout << " 4 " << flush;
// fully filled stack - larger capacity
Stack st11(2);
assert(st11.getCapacity() == 2);
st11.push(3);
st11.push(7);
assert(st11.getTop() == 7);
st11.setCapacity(3);
assert(st11.getCapacity() == 3);
cout << " 5 " << flush;
cout << " Passed!" << endl;
}
当我通过注释其余部分分别运行测试的每个部分时,一切正常。测试的每个部分均通过。但是,当我组合这些部分并尝试运行整个测试时,出现以下错误:
*检测到glibc ** * /home/.../StackProject:malloc():内存损坏(快速):0x0000000001e86030 *
使用调试器,我将问题缩小到在堆栈中创建myArray的范围。例如,在测试中成功运行“ 1”后,在“ 2”中的st8(5)中创建myArray会导致程序崩溃。
我感到困惑的主要根源是由于每个部分都单独通过,但它们并非共同通过。我不确定该怎么办。我的方法写错了吗?如果是这样,我应该如何纠正?
谢谢你。
我setCapacity
在下面的代码块中看到了以下问题:
if(newCapacity != myCapacity){
Item * tempArray = new Item[newCapacity];
if(newCapacity < myCapacity){
for(unsigned i=0; i<newCapacity;i++){
tempArray[i] = myArray[i];
}
} else if (newCapacity > myCapacity) {
for(unsigned i=0; i<myCapacity; i++){
tempArray[i] = myArray[i];
}
}
// When newCapacity > myCapacity, myArray does not
// have enough space for this loop.
// Say myCapacity = 5 and newCapacity = 7
// Accessing myArray[5] and myArray[6] is a problem.
for(unsigned i=0; i<newCapacity; i++){
myArray[i] = tempArray[i];
}
// You are deleting the newly allocated array, even though you are using
// the wrong delete operator.
// myArray still points to the old allocated memory.
delete tempArray;
}
您需要的是:
if(newCapacity != myCapacity){
Item * tempArray = new Item[newCapacity];
if(newCapacity < myCapacity){
for(unsigned i=0; i<newCapacity;i++){
tempArray[i] = myArray[i];
}
} else if (newCapacity > myCapacity) {
for(unsigned i=0; i<myCapacity; i++){
tempArray[i] = myArray[i];
}
}
// Need to delete the old array and keep the new array.
Item* oldArray = myArray;
myArray = tempArray;
// Use the array delete operator, not the simple delete operator.
delete [] oldArray;
}
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