PortAudio: Pa_StartStream() crashes Game Maker when used in DLL - c++

Question

I want to use PortAudio in Game Maker by using a DLL.
I made the callback function in C++ and used that to calculate the frequency of the incoming sample stream. In the DLL I made a few export functions: one that initiates the stream, one that closes the stream and one that gets the frequency variable generated by the callback.
Now when I called the PortAudioStart() function in Game Maker, the game shut down without any warning/error/message of any kind. I put MessageBox()'es in between the lines of code, to check what was the source of the crash. It showed the first, second and third ones, and then it crashed, not even showing the error MessageBox. So it turned out that Pa_StartStream() caused it.
Now I wonder: why does this crash occur, and how can I fix it?
Note: I tested this DLL by letting a C++ program call it, and in that case it worked totally as planned.
I am using GM8.0 and NetBeans 7.3 with the gcc compiler from Cygwin 4.
The start and end functions (leaving out all includes and definitions of global variables):
#define GMEXPORT extern "C" __declspec (dllexport)
GMEXPORT double __cdecl PortAudioStart() {
err = Pa_Initialize();
if( err != paNoError ) goto error;
MessageBoxA(NULL, "1", "PortAudio DLL", MB_ICONINFORMATION);
inputParameters.device = Pa_GetDefaultInputDevice(); /* default input device */
if (inputParameters.device == paNoDevice) {
goto error;
}
inputParameters.channelCount = 1; /* mono input */
inputParameters.sampleFormat = PA_SAMPLE_TYPE;
inputParameters.suggestedLatency = Pa_GetDeviceInfo( inputParameters.device )->defaultLowInputLatency;
inputParameters.hostApiSpecificStreamInfo = NULL;
MessageBoxA(NULL, "2", "PortAudio DLL", MB_ICONINFORMATION);
err = Pa_OpenStream(
&stream,
&inputParameters,
NULL, //&outputParameters
SAMPLE_RATE,
FRAMES_PER_BUFFER,
0,
PaCallback,
NULL );
if( err != paNoError ) goto error;
MessageBoxA(NULL, "3", "PortAudio DLL", MB_ICONINFORMATION);
err = Pa_StartStream( stream );
if( err != paNoError ) goto error;
MessageBoxA(NULL, "4", "PortAudio DLL", MB_ICONINFORMATION);
return 1;
error:
MessageBoxA(NULL, "Apparently it doesn't work!", "PortAudio DLL", MB_ICONINFORMATION);
Pa_Terminate();
return 0;
}
GMEXPORT double __cdecl PortAudioEnd() {
err = Pa_CloseStream( stream );
if( err != paNoError ) goto error;
Pa_Terminate();
return 1;
error:
MessageBoxA(NULL, "Apparently it doesn't work!", "PortAudio DLL", MB_ICONINFORMATION);
Pa_Terminate();
return 0;
}
GMEXPORT double __cdecl getFreq()
{
if (Pa_IsStreamStopped(stream) == 0)
{
return frequency; // this variable is constantly changed in the callback function
}
else
{
return 0;
}
}
void calculateFreq(bool sign)
{
unsigned int j;
bool check;
diffsamp = maxsamp - minsamp;
if (!sign)
{
diffsampmax = max((diffsampmax*.85), (double)diffsamp);
maxsamp = 0;
}
if (sign)
{
diffsampmax = max((diffsampmax*.85), (double)diffsamp);
minsamp = 0;
}
check = ( diffsamp > max(25.0,diffsampmax*.90) );
if (sign == lastsign)
{
check = false;
}
if (check)
{
if (timepassed - peaks[0] < 500)
{
for ( j=numpeaks-1; j>0; j-- )
{
peaks[j] = peaks[j-1];
}
}
else
{
for ( j=0; j<numpeaks; j++ )
{
peaks[j] = 0;
}
}
peaks[0] = timepassed;
double diff = peaks[0]-peaks[numpeaks-1];
double peaktime = diff/(numpeaks-1)*2; //*2 because maxdiff is at +>- and ->+
frequency = 1/((double)peaktime/(double)SAMPLE_RATE);
if (peaks[numpeaks-1] <= 0 || frequency < 20) frequency = 0;
lastsign = sign;
}
}
static int PaCallback( const void *inputBuffer, void *outputBuffer,
unsigned long framesPerBuffer,
const PaStreamCallbackTimeInfo* timeInfo,
PaStreamCallbackFlags statusFlags,
void *userData )
{
const SAMPLE *in = (const SAMPLE*)inputBuffer;
unsigned int i;
unsigned int j;
(void) timeInfo; // Prevent unused variable warnings.
(void) statusFlags;
(void) userData;
SAMPLE samp;
if( inputBuffer == NULL )
{
//nothing happens
}
else
{
for( i=0; i<framesPerBuffer; i++ )
{
timepassed += 1;
samp = *in++;
changed = false;
if (samp > 0)
{
if (!sign)
{
sign = true;
changed = true;
}
maxsamp = max(maxsamp,samp);
}
else
{
if (sign)
{
sign = false;
changed = true;
}
minsamp = min(minsamp,samp);
}
if (changed)
{
calculateFreq(sign);
}
}
}
return paContinue;
}
GML:
//// Script: pa_init()
globalvar _pa_freq,_pa_start,_pa_end;
var dll_name;
dll_name = "c:\Users\<Username>\Documents\NetBeansProjects\GMDLLtest\dist\Debug\Cygwin_4.x-Windows\libGMDLLtest.dll";
_pa_freq = external_define(dll_name, "getFreq", dll_cdecl, ty_real, 0);
_pa_start = external_define(dll_name, "PortAudioStart", dll_cdecl, ty_real, 0);
_pa_end = external_define(dll_name, "PortAudioEnd", dll_cdecl, ty_real, 0);
////--------------------------------------------------------------------------------
//// Script: pa_start()
return external_call(_pa_start);
////--------------------------------------------------------------------------------
//// Script: pa_end()
return external_call(_pa_end);
////--------------------------------------------------------------------------------
//// Script: pa_freq()
return external_call(_pa_freq);
P.S: If anything is unclear, please ask, my knowledge of C++ isn't really outstanding.