C ++：通过指针访问主类的std :: vector的类出错

Question

I'm building my C++ project with VS2012 Express, Platform Toolset v100, and with openFrameworks 0.7.4.

I have a class called NameRect and this is part of the .h file:

void config(int cx, int cy, int cw, int ch, std::string cname) {
    x = cx;
    y = cy;
    w = cw;
    h = ch;
    name = cname;

    dead = false;
}

void branch(int iterants, std::vector<NameRect> *nrs) {
    for (int i = 0; i < iterants; i++) {
        NameRect nnr;
        nnr.config(x + w, y - iterants * h / 2 + i * h, w, h, "cb");

        children.push_back(nnr);
        nrs->push_back(nnr);
    }
}

void render() {
    if (!dead) {
        ofSetColor(ofRandom(0, 255), ofRandom(0, 255), ofRandom(0, 255), 0);
        ofRect(x, y, w, h);
    }
}

And there's the code in my testApp.cpp :

//--------------------------------------------------------------
void testApp::setup(){
    ofSetWindowShape(800, 600);

    nr.config(0, 300, 50, 10, "cb");
    nrs.push_back(nr);
}

//--------------------------------------------------------------
void testApp::update(){
    if (ofRandom(0, 50) <= 1 && nrs.size() < 100) {
        for (int cnri = 0; cnri < nrs.size(); cnri++) {
            if (ofRandom(0, nrs.size() - cnri) <= 1) {
                nrs[cnri].branch(2, &nrs);
            }
        }
    }
}

//--------------------------------------------------------------
void testApp::draw(){
    for (int di = 0; di < nrs.size(); di++) {
        nrs[di].render();
    }
}

And when I actually build (succeeds) this project and run it, it gives me such an error:

I take a look at the local variables watch and it shows such large integer values!

What is the problem?

Answer 1

branch() is modifying the vector array which is passed in as the second parameter.

This means when you call nrs[cnri].branch(2, &nrs) from testApp::update() the underlying array structure is modified. This will lead to unpredictable results and will surely cause your access violation.

Answer 2

your problem #1 is nrs[cnri].branch(2, &nrs); , you may be reallocating memory where nrs[cnri] is residing from inside branch() when doing push_back()

your problem #2, which you'll face once you have started including your header to multiple cpp files, is the way you define functions. If you define them in the header put "inline" otherwise you'll have the same function defined in multiple places.