I'm trying to change a code written in C++ and run it on Raspberry Pi. It is an opensource code called freelss (https://github.com/hairu/freelss) and it's a laser scanner software. I tried to change some parts. For example, I expanded the system with some i2c chips and some buttons. Now I have changed the main.cpp and the main.h to scan the buttons. Everything works fine but now I wanted to have a button that starts the scanning process if I push it.
Scanner (*scanner_Max);
std::cout << "before the first function" << std::endl;
scanner_Max->setTask(Scanner::GENERATE_SCAN);
std::cout << "after the first function" << std::endl;
Now, if I push the button, It says "before the first function" goes into the setTask function and stays there. It never comes back. So I never get the message "after the first function".
void Scanner::setTask(Scanner::Task task)
{
std::cout << "setTask starts" << std::endl;
m_task = task;
}
This is the function in scanner.cpp. I always get the "setTask starts" but it won't come back to the main programm. Can please someone help me with the code?
Greets, Max
In the code you have shown you have not created an instance of Scanner, just a pointer.
Are you missing a:
scanner_Max = new Scanner ();
Or have you just not shown this?
Related
I couldn't come up with a better title, so feel free to give suggestions.
I tried to follow OneLoneCoder's tutorial on sound synthesizing, I'm only halfway through the first video and my code already throws an exception.
All I did was downloading his olcSoundMaker.h from his github, and copying the entry point:
#include <iostream>
#include "olcNoiseMaker.h"
double make_noise(double time)
{
return 0.5 * sin(440.0 * 2 * PI * time);
}
int main()
{
std::wcout << "Synthesizer, part 1" << std::endl;
std::vector<std::wstring> devices = olcNoiseMaker<short>::Enumerate();
for (auto d : devices)
{
std::wcout << "Found output device: " << d << std::endl;
}
olcNoiseMaker<short> sound(devices[0], 44100, 1, 8, 512);
sound.SetUserFunction(make_noise);
while (1) { ; }
return EXIT_SUCCESS;
}
In the video he runs this just fine; for me, it starts producing a sound, then after 60-80 iterations of the while (1) loop, it stops and raises this:
Unhandled exception thrown: write access violation.
std::_Atomic_address_as<long,std::_Atomic_padded<unsigned int> >(...) was 0xB314F7CC.
(from the <atomic> header file, line 1474.)
By stepping through the code with VS I didn't find out much, except that it happens at different times during every run, which may mean it has something to do with multithreading, but I'm not sure since I'm not very familiar with the topic.
I found this question which is similar, but even though it says [SOLVED] it doesn't show me the answers.
Anyone that can help to get rid of that exception?
I'm writing in pure c++11 and want to do a simple 'wait x seconds and turn on a member variable' after turning it off. The member variable of the class in this example is a flag for 'animating'.
cout << "stop animating!" << endl;
this->animating = false;
async(launch::async, [this] ()
{
this_thread::sleep_for(chrono::seconds{8});
this->animating = true;
std::cout << "start animating!" << std::endl;
});
cout << "i'm here" << endl;
the this_thread::sleep_for blocks the entire program from continuing on (even though it is inside an async thread). because i dont see "I'm here" 8 seconds later. If the above code worked as intended, i would see "I'm here" immediately after "stop animating". This blocking is a problem for me because it locks up everything I care about like continuing to process 'input' like keyboard events, and the program also stops 'drawing' other objects on the screen.
Does anyone know how to achieve a simple delayed and async change of a member variable using standard c++11 (no frameworks like boost please)
in iOS it is very simple:
// Delay execution of my block for 10 seconds.
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 10 * NSEC_PER_SEC),
dispatch_get_main_queue(), ^
{
//do whatever, 10 seconds later
});
As per #user2176127 's comment - have you tried this? :
cout << "stop animating!" << endl;
this->animating = false;
std::thread delay_thread(
[this]() {
this_thread::sleep_for(chrono::seconds{8});
this->animating = true;
std::cout << "start animating!" << std::endl;
}
);
delay_thread.detach();
std::cout << "I'm here" << std::endl;
Also note you likely need to wrap the animating member in an std::atomic<>, i.e. if it was bool it now becomes an std::atomic<bool>, so as to ensure your main thread notices the change when it actually happens. (Using volatile won't help.)
I'm wondering what the best way to detect a high DPI display is. Currently I'm trying to use SDL_GetDisplayDPI (int, *float, *float, *float), however this has only returned errors on the two different computers I tested with (MacBook Pro running OS X 10.11.5 and iMac running macOS 10.12 Beta (16A238m)). For reference, my code is bellow.
float diagDPI = -1;
float horiDPI = -1;
float vertDPI = -1;
int dpiReturn = SDL_GetDisplayDPI (0, &diagDPI, &horiDPI, &vertDPI);
std::cout << "GetDisplayDPI() returned " << dpiReturn << std::endl;
if (dpiReturn != 0)
{
std::cout << "Error: " << SDL_GetError () << std::endl;
}
std::cout << "DDPI: " << diagDPI << std::endl << "HDPI: " << horiDPI << std::endl << "VDPI: " << vertDPI << std::endl;
Unfortunately, this is only giving me something like this:
/* Output */
GetDisplayDPI() returned -1
Error:
DDPI: -1
HDPI: -1
VDPI: -1
Not Retina
I also tried comparing the OpenGL drawable size with the SDL window size, but SDL_GetWindowSize (SDL_Window, *int, *int) is returning 0s, too. That code is bellow, followed by the output.
int gl_w;
int gl_h;
SDL_GL_GetDrawableSize (window, &gl_w, &gl_h);
std::cout << "GL_W: " << gl_w << std::endl << "GL_H: " << gl_h << std::endl;
int sdl_w;
int sdl_h;
SDL_GetWindowSize (window, &sdl_w, &sdl_h);
std::cout << "SDL_W: " << sdl_w << std::endl << "SDL_H: " << sdl_h << std::endl;
/* Output */
GL_W: 1280
GL_H: 720
SDL_W: 0
SDL_H: 0
It's entirely possible that I'm doing something wrong here, or making these calls in the wrong place, but I think more likely is that I'm on the wrong track entirely. There's a hint to disallow high-dpi canvases, so there's probably a simple bool somewhere, or something that I'm missing. I have certainly looked through the wiki, and checked Google, but I can't really find any help for this. Any suggestions or feedback are welcome!
Thank you for your time!
I know I'm not answering your question directly, and want to reiterate one thing you tried.
On a Macbook pro, when an SDL window is on an external display, SDL_GetWindowSize and SDL_GL_GetDrawableSize return the same values. If the window is on a Retina screen, they're different. Specifically, the drawable size is 2x larger in each dimension.
I was using a .framework installation of SDL when I encountered this issue. For an unrelated reason, I trashed the .framework SDL files (image and ttf as well), and built SDL from source (thus transitioning to a "unix-style" SDL-installation). To my surprise, SDL_GetDisplayDPI () is now returning 0, setting the values of DDPI, HDPI, and VDPI, to 109 on a non-retina iMac, and 113.5 on a retina MacBook Pro. I'm not certain that these are correct/accurate, but it is consistent between launches, so I'll work with it.
At this point, I'm not sure if it was a bug, which has been fixed in the repo, or was an issue with my .framework files. On a somewhat unrelated note, SDL_GetBasePath () and SDL_GetPrefPath (), which also weren't working, now return the expected values. If you're also experiencing any of these problems on macOS, try compiling and installing SDL from source (https://hg.libsdl.org/SDL).
Thanks for your input, everyone!
I have a problem with my program : I have a memory leak. I know it because when I look at the memory usage it never stop increasing, and then the program crash.
I have remarked that it happens because of this line (when I comment it there is no problem) :
replica[n].SetTempId(i+1); // FUITE MEMOIRE SUR CETTE LIGNE !!
I have checked that n is never bigger than the size of my array (which is a vector type, see below).
My class :
class Replica
{
/* All the functions in this class are in the 'public:' section */
public:
Replica();
~Replica();
void SetEnergy(double E);
void SetConfName(string config_name);
void SetTempId(int id_temp);
int GetTempId();
string GetConfName();
double GetEnergy();
void SetUp();
void SetDown();
void SetZero();
int GetUpDown();
/* All the attributes in this class are in the 'private:' section */
private:
double m_E; // The energy of the replica
string m_config_name; // The name of the config file associated
int m_id_temp; // The id of the temperature where the spin configuration is.
int m_updown;
};
The method
void Replica::SetTempId(int id_temp)
{
m_id_temp=id_temp;
}
I initialised my object like this :
vector<Replica> replica(n_temp); // we create a table that will contain information on the replicas.
The constructor :
Replica::Replica() : m_E(0), m_config_name(""), m_updown(0), m_id_temp(0)
{
}
How I initialize my vector :
for(int i=0; i<=n_temp-1 ; i++) // We write the object replica that will contain information on a given spin configuration.
{
string temp_folder="";
temp_folder= spin_folder + "/T=" + to_string(Tf[i]) + ".dat";
replica[i].SetEnergy(Ef[i]+i); // we save the energy of the config (to avoid to calculate it)
replica[i].SetConfName(temp_folder); // we save the name of the file where the config is saved (to avoid to have huge variables that will slow down the program)
replica[i].SetTempId(i);
replica[i].SetZero();
if(i==0)
replica[i].SetDown();
if(i==(n_temp-1))
replica[i].SetUp();
}
I am a beginner in C++ so it is probably a basic mistake.
Thank you for your help !
I have read your answers.
But it is hard to write a minimal code : I tried to delete some stuff but as soon as I delete lines it works.
In fact the problem is very "random", for example when I delete my line :
replica[n].SetTempId(i+1);
it works, but I can have this line not deleted but when I delete an other line of my code it will also works (I dont know if you see what I mean).
The bug is very hard to find because of this "randomness"...
I also can say that when it crash the program says me :
terminate called after throwing an instance of 'std::bad_alloc'
what(): std::bad_alloc
So, could you give me guess on what could cause this error (because I don't arrive to write the minimal code).
I don't do dynamic allocation on my code.
The structure of my code is like this :
while(Nsw_c<Nsw)
{
cout << "test1";
// a
// lot
// of
// code
// with some Nsw_c++
// and this cout at the end of the loop
cout << " Nsw_c : " << Nsw_c << endl << " i " << i << " compteur_bug " << compteur_bug;
}
cout << "test2";
It ALWAYS freeze on this cout above which is at the end of the loop.
I know this because neither test2 or test1 are displayed when it freezes and it is the next cout.
Nsw, Nsw_c, i are integers that are lower than 100 (they are not too big).
To be more precise, if I replace the cout just at the end of the loop by another cout like this :
cout << " test ";
It will also freeze at the same place.
In fact the program always freeze at the end of my while (juste before analysing the condition).
But Nsw and Nsw_c are not big at all so that's why it is strange.
I tried to replace the condition Nsw_c < Nsw just by "1" and it didn't freeze anymore. So it is probably a problem with the condition but both are just "normal" integers so...
Thanks !
I have launched gdb (i just learnt to use it) and i wrote :
catch throw std::bad_alloc
The debugger then do this (I don't know if it can help) :
not stopped at a C++ exception catchpoint
Catchpoint 1 (exception thrown), 0xb7f25290 in __cxa_throw () from /usr/lib/i386-linux-gnu/libstdc++.so.6
I'm using Boost coroutine library, and I need my coroutine to be re-entrant.
This means I should be able to start the coroutine from the beginning multiple times.
What are some options?
My current workaround is to re-create the fresh coroutine every time:
boost::coroutines::coroutine<int>::pull_type *source = new boost::coroutines::coroutine<int>::pull_type(
[&](boost::coroutines::coroutine<int>::push_type& sink){
sink(0);
cout << "Hello world!" << endl;
});
(*source)();
source = new boost::coroutines::coroutine<int>::pull_type(
[&](boost::coroutines::coroutine<int>::push_type& sink){
sink(0);
cout << "Hello world!" << endl;
});
(*source)();
source = new boost::coroutines::coroutine<int>::pull_type(
[&](boost::coroutines::coroutine<int>::push_type& sink){
sink(0);
cout << "Hello world!" << endl;
});
(*source)();
Because the coroutines from boost.coroutine are stackfull you can't start them multiple times.
It is not clear from your example what you want to do:
print "Hello world!" mutiple times -> use a loop inside the coro-fn
some kind of backtracking/checkpointing -> could be done with coroutiens, but needs some additional work
I don't at all see what's wrong with creating a fresh coroutine every time - they're not expensive to create.
If you have a lot of data in your coroutine so it's expensive to construct, move it all off into some data class and pass a reference to it to your coroutine.