OpenAl Beep function fails with more threads - c++

Question

I tried to write a Beep function using OpenAl. But only a few threads of the function can be run. The following code fails after a while:
#include <cmath>
#include <iostream>
#include <thread>
using namespace std;
#include <AL/alut.h> // OpenAl
void init_al()
{
const char *defname = alcGetString(NULL, ALC_DEFAULT_DEVICE_SPECIFIER);
ALCdevice* dev = alcOpenDevice(defname);
ALCcontext *ctx = alcCreateContext(dev, NULL);
alcMakeContextCurrent(ctx);
}
void exit_al()
{
ALCcontext* ctx = alcGetCurrentContext();
ALCdevice* dev = alcGetContextsDevice(ctx);
alcMakeContextCurrent(0);
alcDestroyContext(ctx);
alcCloseDevice(dev);
}
void Beep(float freq = 440, float seconds = 0.5)
{
init_al();
ALuint buf;
alGenBuffers(1, &buf);
unsigned sample_rate = 10000;
size_t buf_size = seconds * sample_rate;
short* samples = new short[buf_size];
if(samples == 0)
{
cout<< "It seems there is no more heap memory. Sorry we cannot make a beep!";
}
for(unsigned i = 0; i < buf_size; i++)
samples[i] = 32760*sin(2*M_PI*i*freq/sample_rate);
alBufferData(buf,AL_FORMAT_MONO16,samples,buf_size,sample_rate);
ALuint src;
alGenSources(1,&src);
alSourcei(src,AL_BUFFER,buf);
alSourcePlay(src);
alutSleep(seconds + 0.5);
delete[] samples;
exit_al();
}
int main()
{
for(int i = 1; i < 1000; i++)
{
thread t(Beep, 440,0.5);
t.detach();
alutSleep(0.01);
}
}
What's wrong with Beep function? And how can I fix it?
I used this Beep function in a normal program where a problem occured. I have reproduced the error in program above. The problem is that Beeb becomes unresponsive after a while, even if you leave it alone for a few seconds to complete its previous tasks. So it uses something up and doesn't return it. If you change 1000 to 20 nothing changes.

Answer 1

I added 3 new lines to the program and placed init_al and exit_al in main and it seems the problem is solved now. btw, I don't know why is it necessary to place init_al and exit_al in main so this is just a partial answer to the question:
#include <cmath>
#include <iostream>
#include <thread>
using namespace std;
#include <AL/alut.h> // OpenAl
void init_al()
{
const char *defname = alcGetString(NULL, ALC_DEFAULT_DEVICE_SPECIFIER);
ALCdevice* dev = alcOpenDevice(defname);
ALCcontext *ctx = alcCreateContext(dev, NULL);
alcMakeContextCurrent(ctx);
}
void exit_al()
{
ALCcontext* ctx = alcGetCurrentContext();
ALCdevice* dev = alcGetContextsDevice(ctx);
alcMakeContextCurrent(0);
alcDestroyContext(ctx);
alcCloseDevice(dev);
}
void Beep(float freq = 440, float seconds = 0.5)
{
ALuint buf;
alGenBuffers(1, &buf);
unsigned sample_rate = 10000;
size_t buf_size = seconds * sample_rate;
short* samples = new short[buf_size];
if(samples == 0)
{
cout<< "It seems there is no more heap memory. Sorry we cannot make a beep!";
}
for(unsigned i = 0; i < buf_size; i++)
samples[i] = 32760*sin(2*M_PI*i*freq/sample_rate);
alBufferData(buf,AL_FORMAT_MONO16,samples,buf_size,sample_rate);
ALuint src;
alGenSources(1,&src);
alSourcei(src,AL_BUFFER,buf);
alSourcePlay(src);
alutSleep(seconds + 0.5);
delete[] samples;
alSourceStopv(1,&src); // new line
alDeleteSources(1,&src); // new line
alDeleteBuffers(1,&buf); // new line
}
int main()
{
init_al();
for(int i = 1; i < 1000; i++)
{
thread t(Beep, 440,0.5);
t.detach();
alutSleep(0.01);
cout<< i << "\n";
}
exit_al();
}