Q_DECL_CONSTEXPR inline int QSize::height() const
{ return ht; }

qDebug() << QString("---SETTINGS DEBUG---")+QString("rn")<<
            "netProcPage: "+netProcPage.url()+"rn" <<
            "mapSize.width(): "+QString::number(mapSize.width())+"rn"<<
            "mapSize.height(): "+QString::number(mapSize.height())+"rn"<<
            "mapZoom: "+QString::number(mapZoom)+"rn"<<
            "mappxSize.width(): "+QString::number(mappxSize.width())+"rn"<<
            "mappxSize.height(): "+QString::number(mappxSize.height())+"rn"<<
            "UserCoords[0]: "+QString::number(UserCoords[0])+"rn"<<
            "UserCoords[1]: "+QString::number(UserCoords[1])+"rn"<<
            "mapCoordOffsets[0]: "+QString::number(mapCoordOffsets[0])+"rn"<<
            "mapCoordOffsets[1]: "+QString::number(mapCoordOffsets[1])+"rn"<<
            "getWindowSize.width(): "+QString::number(getWindowSize.width())+"rn"<<
            "getWindowSize.height(): "+QString::number(getWindowSize.height())+"rn"<<
            "mappxOffsets[0]: "+QString::number(mappxOffsets[0])+"rn"<<
            "mappxOffsets[1]: "+QString::number(mappxOffsets[1])+"rn"<<
            QString("---END SETTINGS DEBUG---")+QString("rn");

mkeMap.genMap(QString("Map1"), tempmapSize, tempmapZoom, mapDisp->ui);

QSize tempmapSize;
tempmapSize = settings->mapSize; //<--- The error might be coming from here, is there an alternative?

#include "settings.h"

Settings::Settings(QWidget *parent)
{

    netProcPage = "http://localhost:81";

    // Max image size is 32767x32767 pixels (divided by 4*mapZoom since 4 panes are used at mapZoom zoom)
    // If max mapZoom is 20, max size of map is 409x409, or 408x408 to keep it even
    mapSize.setWidth(250);
    mapSize.setHeight(250);

    mapZoom = 10;
    mappxSize.setWidth(mapSize.width()*mapZoom);
    mappxSize.setHeight(mapSize.height()*mapZoom);

    //downloadMap(netProcPage,"getMap","Username","Password");
    //makeMap("bingbong",mapSize,mapZoom);
    UserCoords[0] = 0;
    UserCoords[1] = 0;
    mapCoordOffsets[0] = UserCoords[0] + .5 * mapSize.width();
    mapCoordOffsets[1] = UserCoords[1] + .5 * mapSize.height();
    //getWindowSize.setWidth(parent->width());
    //getWindowSize.setHeight(parent->height());
    getWindowSize.setWidth(500);
    getWindowSize.setHeight(500);
    mappxOffsets[0] = UserCoords[0]*mapZoom + .5 * getWindowSize.width() - .5 * mappxSize.width();
    mappxOffsets[1] = UserCoords[1]*mapZoom + .5 * getWindowSize.height() - .5 * mappxSize.height();
}

void Settings::debug()
{
    qDebug() << QString("---SETTINGS DEBUG---")+QString("rn")<<
                "netProcPage: "+netProcPage.url()+"rn" <<
                "mapSize.width(): "+QString::number(mapSize.width())+"rn"<<
                "mapSize.height(): "+QString::number(mapSize.height())+"rn"<<
                "mapZoom: "+QString::number(mapZoom)+"rn"<<
                "mappxSize.width(): "+QString::number(mappxSize.width())+"rn"<<
                "mappxSize.height(): "+QString::number(mappxSize.height())+"rn"<<
                "UserCoords[0]: "+QString::number(UserCoords[0])+"rn"<<
                "UserCoords[1]: "+QString::number(UserCoords[1])+"rn"<<
                "mapCoordOffsets[0]: "+QString::number(mapCoordOffsets[0])+"rn"<<
                "mapCoordOffsets[1]: "+QString::number(mapCoordOffsets[1])+"rn"<<
                "getWindowSize.width(): "+QString::number(getWindowSize.width())+"rn"<<
                "getWindowSize.height(): "+QString::number(getWindowSize.height())+"rn";//<<
                //"mappxOffsets[0]: "+QString::number(mappxOffsets[0])+"rn"<<
                //"mappxOffsets[1]: "+QString::number(mappxOffsets[1])+"rn"<<
                //QString("---END SETTINGS DEBUG---")+QString("rn");
}

QSize* Settings::getmapSize()
{
    return &mapSize;
}

int Settings::getmapZoom()
{
    return mapZoom;
}

void makeMap::genMap(QString name, QPointF* inSize, int* zoom, Ui::MapDisp* ui)
{
    QVector<QString> mapvector;
    QPointF mapSize = *inSize; // <--- The problem is right here

...
}

QPointF* tempmapSize;
tempmapSize = settings->getmapSize();
int* tempmapZoom = settings->getmapZoom();
mkeMap.genMap(QString("Map1"), tempmapSize, tempmapZoom, mapDisp->ui);

Starting C:program-debug.exe...
ASSERT failure in QVector<T>::operator[]: "index out of range", file ../../../../../Qt/5.2.0/mingw48_32/include/QtCore/qvector.h, line 369
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.
C:program-debug.exe exited with code 3

void makeMap::genMap(QString name, QPointF* inSize, int* zoom, Ui::MapDisp* ui)
{
    QVector<QString> mapvector;
    QPointF mapSize = *inSize; //<---Here's the segmentation fault
    /* Using this instead of the above works, as well as replacing zoom which causes another segmentation fault when dereferenced
    QPointF mapSize;
    mapSize.setX(250);
    mapSize.setY(250);
    int zoom0 = 10;
    */

    QFile file(name+"_"+QString::number(mapSize.x())+"x"+QString::number(mapSize.y())+".rtsmap");
    file.open(QIODevice::WriteOnly | QIODevice::Text);
    QTextStream out(&file);
    mapvector.resize(mapSize.x() * mapSize.y());
    for(int x = 0; x < mapSize.x(); x++){
        for(int y = 0; y < mapSize.y(); y++){
            uint decimalcolor = (((qSin(x)+1) + (qSin(y)+1))/4)>1?16777215:(((qSin(x)+1) + (qSin(y)+1))/4)*16777214;
            QString hexadecimalcolor;
            hexadecimalcolor.setNum(decimalcolor,16);
            mapvector[index(x, y, mapSize)] = "#" + hexadecimalcolor;
            //drawRect(x*10,y*10,10,10,"#"+hexadecimalcolor,zoom);
            out << "#" << hexadecimalcolor+'n';
        }
    }
    file.close();
    drawMap(mapvector,zoom0,ui,mapSize);
}

MapCtrl::MapCtrl(QWidget *parent, Settings *settingsIn) :
    QWidget(parent),
    ui(new Ui::MapCtrl)
{
    ui->setupUi(this);
    mapDisp = new MapDisp(parent, settingsIn);
    addMap();
    settings = settingsIn;
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    wScr = new WelcomeScreen(this);
    Settings *settings = new Settings(this);
    mapCtrl = new MapCtrl(parent,settings);
    ...
}

MapCtrl::MapCtrl(QWidget *parent, Settings *settingsIn) :
    QWidget(parent),
    ui(new Ui::MapCtrl)
{
    ui->setupUi(this);
    mapDisp = new MapDisp(parent, settingsIn);
    addMap();
    qDebug() << "bingbong!!" << settingsIn->mapSize.x();
    settings = settingsIn;

}

MapCtrl::MapCtrl(QWidget *parent, Settings *settingsIn) :
    QWidget(parent),
    ui(new Ui::MapCtrl)
{
    ui->setupUi(this);
    mapDisp = new MapDisp(parent, settingsIn);

    qDebug() << "bingbong!!" << settingsIn->mapSize.x();
    settings = settingsIn;
    addMap();
}

QSize Settings::getmapSize() const
{
    return mapSize;
}

mapCoordOffsets = UserCoords + (toPoint(mapSize) * .5);

static QPointF toPoint(const QSize & size) {
  return QPointF(size.width(), size.height());
}

void makeMap::genMap(..., QPointF* inSize, int* zoom, ...)

MapParams makeMap::genMap(...);

MapParams makeMap::genMap(..., MapParams params) {
   ...
   params.size = ...;
   params.zoom = ...;
   ...
   return params;
}