I'm using it in DllMain.
I don't think DAQmx ANSI C examples show handle problem because they are all single executable file example. I'll attach sample source files for this case.
Build first source as DLL file name as SampleDAQLibrary.dll and check them with second source. If you did not call cleanFunc in DllMain detach case, you can see increased handle count in task manager.
#include <stdio.h>
#include <NIDAQmx.h>
#include <Windows.h>
#include <cvirte.h>
/*****************************************************************************/
typedef void (__cdecl *CleanFunc)(int);
static void cleanUp(void)
{
unsigned int *p;
CleanFunc func;
p = (unsigned int *)DAQmxCreateTask;
func = (CleanFunc)(p - (0x74e0 / 4));
func(4);
}
__declspec(dllexport) void TestAnalogIn(void)
{
TaskHandle handle;
double buff[256];
int arraySize, readSize;
if (DAQmxCreateTask("", &handle) != 0) {
printf("Error on DAQmxCreateTask\n");
return;
}
if (DAQmxCreateAIVoltageChan(handle,
"Dev1/ai0",
"",
DAQmx_Val_RSE,
-5,
5,
DAQmx_Val_Volts,
NULL) != 0) {
printf("Error on DAQmxCreateAIVoltageChan\n");
goto exit;
}
arraySize = 4;
if (DAQmxReadAnalogF64(handle,
DAQmx_Val_Auto,
1.0,
DAQmx_Val_GroupByChannel,
buff,
arraySize,
&readSize,
NULL) != 0) {
printf("Error on DAQmxReadAnalogF64\n");
}
printf("Read %d samples\n", readSize);
exit:
if (DAQmxStopTask(handle) != 0) {
printf("Error on DAQmxStopTask\n");
}
if (DAQmxClearTask(handle) != 0) {
printf("Error on DAQmxClearTask\n");
}
}
/*****************************************************************************/
int __stdcall DllMain (HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
{
switch (fdwReason)
{
case DLL_PROCESS_ATTACH:
if (InitCVIRTE (hinstDLL, 0, 0) == 0) {
return 0;
}
break;
case DLL_PROCESS_DETACH:
CloseCVIRTE();
/* call cleanUp before unloaded */
cleanUp();
break;
}
return 1;
}
int __stdcall DllEntryPoint (HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
{
/* Included for compatibility with Borland */
return DllMain (hinstDLL, fdwReason, lpvReserved);
}
#include <Windows.h>
#include <stdio.h>
#include <stdlib.h>
/*****************************************************************************/
typedef void (*testFunc)(void);
static void test(void)
{
HMODULE handle;
testFunc func;
handle = LoadLibrary("SampleDAQLibrary.dll");
if (!handle) {
printf("Error on load library\n");
return;
}
func = (testFunc)GetProcAddress(handle, "TestAnalogIn");
if (!func) {
printf("Error on get function address\n");
goto exit;
}
func();
exit:
FreeLibrary(handle);
}
int main(void)
{
int i;
printf("first prerun\n");
test();
printf("Enter to continue\n");
getchar();
for (i = 0; i < 100; ++i) {
printf("run %d\n", i);
test();
}
printf("End\n");
getchar();
return (0);
}
