C ++程式当机

Question

I'm doing a project with C++ and my program keeps crashing down when I try to run it...here is my code (two files: main.cpp and PlacementHead.cpp ):

main.cpp:

#include <iostream>
#include <vector>
#include <string>
#include <cstdlib>
#include <ctime>
#include <climits>
#include "PlacementHead.h"

// Main

int main (int argc, char * const argv[]) {

        PlacementHead h1(4,2,1,"aabcbbca");
        PlacementHead h2(4,2,1,"babcabca");

    return 0;
}

PlacementHead.cpp:

#include "PlacementHead.h"
#include <string>
#include <iostream>
#include <string.h>

PlacementHead::PlacementHead(int width, int height, int gap, char* s) {
    width_ = width;
    height_ = height;
    gap_ = gap;
    size_ = width*height;
    set_ = new char[size_];
    from_ = new int[size_];
    original_ = new char[size_];
    strcpy(set_,s);
    strcpy(original_,s);
}

PlacementHead::~PlacementHead() {

}

int PlacementHead::getSize() { return size_; }
int PlacementHead::getHeight() { return height_; }
int PlacementHead::getWidth() { return width_; }
int PlacementHead::getGap() { return gap_; }

char PlacementHead::getNozzle(int i) {
    return set_[i-1];
}

void PlacementHead::setNozzle(int i, char c) {
    set_[i-1] = c;
}

void PlacementHead::markNozzle(int i, int bankPos) {
    set_[i-1] = ' ';
    from_[i-1] = bankPos;
}

int PlacementHead::getNextUnmarkedPos() {
    for (int i=0; i<size_; i++) {
        if (set_[i]!=' ') {
            return i+1;
        }
    }
    return 0;
}

int PlacementHead::getBankPos(int i) {
    return from_[i-1];
}

void PlacementHead::reset() {
    //for (int i=0; i<size_; i++) {
    //  set_[i] = original_[i];
    //}
    strcpy(set_,original_);
}

void PlacementHead::print() {
    std::cout << "placementhead:\n";
    for (int h=height_; h>0; h--) {
        for (int w=width_; w>0; w--) {
            int i = ((h-1)*width_)+w;
            std::cout << getNozzle(i);
        }
        std::cout << "\n";
    }
}

If I try to run the main.cpp, I get this:

Once I got this also (I don't get this every time, which bugs me...):

Now here is also one thing to take into account: If I comment out the second line where PlacementHead h2-object is created the code runs okay, but IF I create more than one PlacementHead-objects the program crashes again...

Any advices what might be causing this? Thank you for any help!! =)

PS

My platform is Windows 7, Codeblocks 12.11 and GNU GCC Compiler

UPDATE:

In case you couldn't see the text on the second picture here it is:

Answer 1

size_ = width*height; should be size_ = (width*height)+1; so the string can be null terminated. Currently you are writing to unallocated memory causing undefined behaviour

Answer 2

You should

• increase size_ by +1 too avoid buffer overrun (or, use std::vector instead, see below)
• disable copy construction/assignment
• add a proper destructor
• use initialization lists
• check the order in which members are declared (since this is also the order in which members are initialized !)
• remove the default constructor, since it doesn't initialize a single member
• include <cstring> instead of <string.h> on modern compilers (so you get namespaces C standard library functions)

Consider using std::vector instead of manual arrays. This will save you much trouble. Think of how you are going to get your constructor exception safe?

Here is a sample fixing all of the above:

#include <iostream>
#include <vector>
#include <cstring>

struct PlacementHead {
    int width_, height_, gap_;
    size_t size_;

    std::vector<char> set_, original_;
    std::vector<int> from_;

    PlacementHead(int width, int height, int gap, const char* s) :
        width_(width),
        height_(height),
        gap_(gap),
        size_(width * height),
        set_(s, s + std::min(strlen(s), size_)),
        original_(set_),
        from_(size_)
    {
        set_.resize(size_);
        original_.resize(size_);

    }

    size_t getSize() { return size_; }
    int getHeight() { return height_; }
    int getWidth() { return width_; }
    int getGap() { return gap_; }

    char getNozzle(int i) { return set_[i - 1]; }

    void setNozzle(int i, char c) { set_[i - 1] = c; }

    void markNozzle(int i, int bankPos) {
        set_[i - 1] = ' ';
        from_[i - 1] = bankPos;
    }

    int getNextUnmarkedPos() {
        for(unsigned i = 0; i < size_; i++) {
            if(set_[i] != ' ') {
                return i + 1;
            }
        }
        return 0;
    }

    int getBankPos(int i) { return from_[i - 1]; }

    void reset() {
        //for (int i=0; i<size_; i++) {
        //  set_[i] = original_[i];
        //}
        set_ = original_;
    }

    void print() {
        std::cout << "placementhead:\n";
        for(int h = height_; h > 0; h--) {
            for(int w = width_; w > 0; w--) {
                int i = ((h - 1) * width_) + w;
                std::cout << getNozzle(i);
            }
            std::cout << "\n";
        }
    }
};

// Main

int main (int argc, char * const argv[]) {

    PlacementHead h1(4,2,1,"aabcbbca");
    PlacementHead h2(4,2,1,"babcabca");

    return 0;
}

Answer 3

You have an off-by-one error in your constructor, as the strings you try to copy are not 8 characters, they are 9. The reason is that all string literals are also containing an extra special string termination character.

If you're using strings in C++, use std::string , it will help you tremendously with problems like these.