Simple if comparison doesn't work with char - c

Question

I am creating a DLL to check when the user presses the close button on the application window, it works fine, then I want to do it so that when _text global variable is empty, no message will be shown.
I can't understand why a simple if (_text != "") doesn't work... am I doing something wrong?
#include <windows.h>
#define export extern "C" __declspec (dllexport)
WNDPROC GameWndProc = NULL;
HWND GameHwnd = NULL;
double _button_result = 0;
char* _text;
char* _title;
LRESULT CALLBACK SubClassWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch(uMsg) {
case WM_CLOSE:
if (_text != "") {
if (MessageBox(GameHwnd, (LPSTR)_text, (LPSTR)_title, MB_YESNO|MB_APPLMODAL) == IDYES) {
_button_result = 1;
return 0;
} else {
return 0;
}
}
_button_result = 1;
return 0;
break;
}
return CallWindowProc(GameWndProc, hwnd, uMsg, wParam, lParam);
}
export double _window_check_close_init(double window_handle, char* _msg_text, char* _msg_title)
{
GameHwnd = (HWND)(int)window_handle;
GameWndProc = (WNDPROC)SetWindowLongPtr(GameHwnd, GWL_WNDPROC, (LONG)SubClassWndProc);
_text = _msg_text;
_title = _msg_title;
if (!GameWndProc) {
return 0;
}
return 1;
}
export double _window_check_close()
{
if (_button_result == 1) {
_button_result = 0;
return 1;
} else {
return 0;
}
}
BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
{
if (fdwReason == DLL_PROCESS_DETACH) {
if (IsWindow(GameHwnd) && GameWndProc) {
SetWindowLongPtr(GameHwnd, GWL_WNDPROC, (LONG)GameWndProc);
}
}
return TRUE;
}

Answer 1

You're checking if the pointer _text is equal to the empty string, not if the string pointed to by _text is equal to the empty string. You probably want to do something like:
if (strlen(_text) !=0)
... rest of your code...

Answer 2

Use strcmp() to compare strings:
if (strcmp(_text, "") != 0) {
}

Answer 3

Just to clarify the difference between pointers and contents of the location to which pointer points:
char* _text : The variable 'text' is a pointer. If you look at it in a debugger it would hold a hex value which would be a memory address. In your case _text holds the address of the string _msg_text
_text != "" : You are comparing two pointers, not their contents. "" in this statement is returning the location of the null string which would again be some hex value which is a memory address.
What you need to do is compare the contents of _text with the null string ""
The above answers are correct.