How to store text in wchar_t pointer parameter

Question

I want to dll export some functions from cpp to dart and in order to do this I need to create a function with a pointer parameter where I will send text.

But after many searches I found no solution that works.

My question is: How to create a function with a wchar_t* parameter, and fill that variable with text? I have no knowledge of cpp pointers, I usually dont code in cpp.

Here is my code, it gives errors:


//extern "C" __declspec(dllexport) 
void getAudioDevices(wchar_t* output, int outSize)
{
    std::vector<DeviceProps> result = EnumAudioDevices(eRender);
    std::wstring listOutput(L"");
    if (!result.empty())
    {
        for (const auto& device : result)
        {
            std::wstring info(L"");
            info += device.name; //PCWSTR
            info += L"\n";
            info += device.iconInfo; //PCWSTR
            info += L"\n";
            info += device.id; //LPWSTR
            info += L"\n";
            info += device.isActive ? L"true" : L"false";
            info += L"\n[][][][]\n";
            listOutput += info.c_str();
        }
    }
    wcscpy_s(output, outSize, listOutput.c_str());
}
int wmain(int argc, WCHAR* argv[])
{
    WCHAR output[1000];
    getAudioDevices(output, sizeof(output));
    cout << output << endl;

}

Maybe declare `outSize` as `size_t` instead of `int` so it will more effectively compile without a warning on 64-bit. `if (!result.empty())` - you don't need this check. — selbie, Jun 24 '22 at 07:04
The output buffer isn't missing the termination character is it? If before the std::cout you output[999] = L'\0'; doesn't suddenly work? — Natio2, Jun 24 '22 at 07:08
@selbie `Run-Time Check Failure #2 - Stack around the variable 'output' was corrupted.` and `: Stack cookie instrumentation code detected a stack-based buffer overrun` — Doger, Jun 24 '22 at 07:08
Side note: `listOutput += info.c_str();` -> `listOutput += info;` — Jabberwocky, Jun 24 '22 at 07:13

score 3 · Accepted Answer · answered Jun 24 '22 at 07:13

sizeof(output) will return the number of bytes the array is. On Windows this will be 2000 instead of 1000 since each wchar_t is 2 bytes long.

But the the value passed to the wcscpy_s is the number of wide characters that your array can hold. Your array can hold 1000 wchar_t's. But your are actually telling wcscpy_s that it can hold more than that.

Change this:

getAudioDevices(output, sizeof(output));

To this:

getAudioDevices(output, sizeof(output)/sizeof(output[0]) );

Declare outSize to be of type size_t as well instead of int

How to store text in wchar_t pointer parameter

1 Answers1