Mac Stringstream returns wrong output

Bugi

Hi we are two students in my class who has a slightly strange experience with string stream on our Qt installation C++

Common trails of setup:

macOS Majave v. 10.14
Qt Creator 4.9.1
Kit: Desktop Qt 5.12.2 clang 64bit (default)

Our Code C++: main.cpp

/#include <iostream>
#include <sstream>
#include <vector>
#include <utility>

std::vector<std::pair<double, int> > readPolynomial(std::string& p);

int main() {
    std::string pstr = "22x^3+2x^2-1x^0";
    std::vector<std::pair<double, int> > poly = readPolynomial(pstr);

    for (unsigned int i = 0; i < poly.size(); ++i) {
        if (i>0) {
            if (poly[i].first > 0) {
                std::cout << "+";
            }
        }
        std::cout << poly[i].first << "x^" << poly[i].second;
    }
    std::cout << std::endl;

    return 0;
}

std::vector<std::pair<double, int> > readPolynomial(std::string& p) {
    std::vector<std::pair<double, int> > poly(3);
    std::stringstream stringstream(p);

    for (size_t i{0}; i < 3; i++) {
        stringstream >>  poly[i].first;
        stringstream.ignore(2);
        stringstream >>  poly[i].second;
    }

    return poly;
}

Output: Terminal

0x^00x^00x^0

Any suggestions?
PS. please be detailed we are first year and new to Qt, C ++, and Terminal command

Update 1:
Im not he best at using the debugging tool.
but at the following link you can fine some pictures of the debugging window.
link debugging Images

Kent-Dorfman

This post is deleted!

Kent-Dorfman

The only real problen I see is that you are not consuming the "+" sign between the terms. On a more broad note, parsing expressions in the way you are doing it is quite limited. What about possible white-space in the input string?

Bugi

@Kent-Dorfman There is only this single input. so will not experience any whitespaces. it is a simpel class Exercise. and our teacher hates mac son no help there.

And the code works fine on windows machine. running QT with MinGW.
All 6 people in our class there is using macOS experience this problem.
that 22 becomes 0, and so does 3 , +2, 2, -2, and 0.
So must be something with our compiler or environment i guess.

fcarney

Run Linux/Windows in a virtual machine in MacOS. You get to keep your Mac and your sanity. This is how I have developed code for a Linux server machine running in Windows.

Konstantin Tokarev

Are you using release or debug build? Does result change if you switch mode?

Try single-stepping your program in debugger and see what happens to string and how is it parsed

Bugi

@Konstantin-Tokarev
I Was using debug build. which always resultet in the output: 0x^00x^00x^0
But if i switch to relaease i get a random output evry time eks:

0x^-19887461000x^-19887461000x^-1988746100
0x^2068517450x^2068517450x^206851745
0x^8690926600x^8690926600x^869092660
....

I now how to insert brake point and running the debug mode.
but don't know how to single stepping. or what to look for in the debug window...

Image of debugging can be fund in dropbox folder...
link debugging Images

Bugi

@fcarney
Don't want to run a virtual machine. in that case I might as well have bought a windows machine and programing on it.
I have Qt installed on my Mac and it should be possible to make it work somehow

mranger90

@Bugi said in Mac Stringstream returns wrong output:

I would suggest changing this:

for (size_t i{0}; i < 3; i++) {

to the more traditional

for (size_t  i = 0; i < 3; i++) {

It's possible that your compiler is having an issue with that kind of initialization

Bugi

@mranger90
I tried it.
but that didn't make any difference.
But as you can see in the pictures of debug from
the above answer. it iterate well through
(I will add the debugging image in the question.)

mranger90

Your images don't show the contents of "poly" so it's hard to tell if it's being set correctly.
try breaking it into pieces like:

    std::vector<std::pair<double, int> > poly;
    std::stringstream stringstream(p);

    for (size_t i{0}; i < 3; i++) {
        std::pair<double, int> tpair;
        stringstream >> tpair.first;
        stringstream.ignore(2);
        stringstream >>  tpair.second;
        poly.push_back(tpair);
    }
    return poly;

And looking at "tpair" to see if stringstream is setting it correctly.

fcarney

What C++ standard is the compiler set to? Can you force it to say -std=c11? Be curious to know what version of the standard it is set to for compiling now. Is the clang setup gcc based or something else? You said it worked in mingw, which is basically gcc. Is it possible to get a gcc compiler for MacOS?

Another option to consider. Completely uninstall your Qt installation and reinstall. I had issues with a Qt install installation where header files were corrupted and all sorts of weird problems. Some things would work, and others would not. I did a drive check in Windows and found corrupted sectors. This caused the corruption of the files. This was in Windows 7 however.

fcarney

The code as presented in the original post works in gcc like @Bugi said about it working in mingw. I tried the following to see if it made any difference:

QMAKE_CXXFLAGS += -std=c++98
QMAKE_CXXFLAGS += -std=c++11
QMAKE_CXXFLAGS += -std=c++14
QMAKE_CXXFLAGS += -std=c++17

I tested each separately, but they did not change the output at all. I get this on output:

22x^3+2x^2-1x^0

System I tested on:
Ubuntu 18.04 Linux
gcc/g++ 7.4.0
64 bit compile

Hope this helps you narrow it down.

fcarney

I just installed clang 7 on Linux and compiled the program like this:

clang++7 main.cpp

This produced "a.out".
I ran this and it produced:

22x^3+2x^2-1x^0

I don't know if clang is different on Linux than on MacOS though. I don't know what version you have either. If you can tell me the version I can see if that works.

Konstantin Tokarev

But if i switch to relaease i get a random output evry time eks:

0x^-19887461000x^-19887461000x^-1988746100

0x^2068517450x^2068517450x^206851745

0x^8690926600x^8690926600x^869092660

This means that you are printing uninitialized variables somehow.

but don't know how to single stepping. or what to look for in the debug window...

https://doc.qt.io/qtcreator/creator-debug-mode.html

You need to look at value of poly[i].second before and after stringstream >> poly[i].second; line. Also look up value of p at this moment, and look at internal data fields of stringstream. If still unclear, put a breakpoint on that line, and press F11 to get as deep into implementation of stringstream as needed

fcarney

I am running Linux so it only took a couple of minutes to install clangs 3.9, 4.0, 5.0, 6.0, and 7.0. I then compiled and ran your code on all of those versions and it produced what it was supposed to produce (22x^3+2x^2-1x^0). So unless you have a really old version of clang my guess is something else is wrong. I have no clue what could be wrong, but my first inclination is to reinstall Qt completely. In my opinion there is nothing wrong with the code itself.

Edit: Then again, 6 other people are having the same problem. So no clue on what could be the issue. Sorry.

Edit 2: @Bugi what does your pro file look like?

Bugi

@mranger90
I don't know if this is what you ment by intialization it in a diffrent way...
(by creating a double and a int to pass the values into instead.) But it made no difference.

std::vector<std::pair<double, int> > readPolynomial(std::string& p)
{
    std::vector<std::pair<double, int> > poly;
    std::stringstream ss(p);

    double coeff;
    int power;

    for (size_t i = 0 ;i < 3; i++) {
        ss >> coeff;
        ss.ignore(2);
        ss >> power;

        poly.push_back(std::make_pair(coeff,power));
    }
    return poly;
}

Images of this code in debug mode se folder debug_2
if you meant something else with your suggestion can you elaborate a little.

The image of the first debug run with the origanal code is also the folder (link above) as debug_1 updatet with visible content of "poly"

And you're code sugesting with "std::pair<double, int > tpair" is also in the folder (link above) as debug_3

mranger90

Ok, this is a head scratcher. As indicated by @fcarney I've run your code, as is on a couple of systems (ubuntu 18.04 with gcc 7.4) and Windows 10 with msvc 2017. And they both produce the expected output.
So the issue seems to be compiler or environment related. And the fact that debug/release builds produce different output seems to indicated that somewhere, something is not being initialized, but in your simple code that would be easy to spot.
The only other issue that pops out on visual inspection is using the variable named "stringstream" which I suppose could cause confusion with the type "stringstream", but one of your tests changes the name to "ss" so that is not the issue.
Try parsing the first parameter as an int instead of a double, or even as a float instead of double to see if that makes a difference.

kshegunov

Be sure the stream's not corrupted:

std::stringstream ss(p);
ss.exceptions(std::stringstream::failbit | std::stringstream::badbit);

try  {
   for (size_t i = 0 ;i < 3; i++) {
        ss >> coeff;
        ss.ignore(2);
        ss >> power;

        poly.push_back(std::make_pair(coeff,power));
    }
}
catch (const std::exception & e)
{
    std::cerr << e.what() << std::endl;
    throw;
}

You'd need the appropriate headers too:

#include <exception>
#include <iostream>

Bugi

@fcarney

I don't think there are many opportunities to change the compiler on macOS. Since the installation settings come with XCode. Actually tried "this" before I started this thread. and had to format my entire pc and reinstall everything.

I treed to type " $ gcc --version " to answer you question. and don't know whether this is useful...

MY-MacBook-Air:~ bugi$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.6.0
Thread model: posix
InstalledDir: Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

I fund this .pro file in the project folder

TEMPLATE = app
CONFIG += console c++11
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += \
        main.cpp

HEADERS +=

I tried reinstalling the latest Qt Open Source version:
Under the instalion setup there is a step where you are installing components: where i have 2 options at this step.
1. is to install as. Qt 5.12.3 -> macOS :
This installation resultet in nothing working at all!
couldn't even compile with the auto-detected kit. Or correct it to something that worked.
So I uninstalled it again (Both time with the MaintenanceTool which removed all files from the system).
I then tried again this time with the other option under installing component.
2. which is to install as. Qt 5.12.2 -> macOS : I was then able to compile my projects again but it made no difference. It is still "0x^00x^00x^0" as output.

I alså tried 3.th, 4.th, and a 5.th time.
3.th time with both option 1. and 2. simultaneously. this resultere in that nothing would compile. again with the auto-kit or any setting (qmake return 2)
The 4.th and 5.th time both time by uninstalling both Qt and XCode. And agin it was only possible to make the qt installation with component: Qt 5.12.2 -> macOS. able to compile any of my projects. still with the wrong output. "0x^00x^00x^0"