Display an int variable in a MessageBox - c++

Question

I am working on an old app written in Visual C++ 6.0. I am trying to display an int variable in a MessageBox for debugging reasons. Here is my code, I thought this would be a simple process, but I am just learning C++. The two lines that are commented I have tried as well with similar errors. Below is the error I am getting.
int index1 = 1;
char test1 = index1;
// char var1[] = index1;
// char *varGo1 = index1;
MessageBox(NULL, test1, "testx", MB_OK);
error C2664: 'MessageBoxA' : cannot convert parameter 2 from 'char' to 'const char *'

Answer 1

Why bother with C-style strings if you tagged C++?
Although Mark Ransom provided MFC solution (which is perfectly valid), here is a Standard C++ one:
int index1 = 1;
std::string test1 = std::to_string(index1);
MessageBoxA(NULL, test1.c_str(), "testx", MB_OK);
References:
std::to_string();
Arrays are evil
Use boost::format for more sophisticated formatting.

Answer 2

int index1 = 1;
char buf[10];
itoa(index1,buf,10);
MessageBox(NULL,buf,"Caption",MB_OK);
Can try this

Answer 3

CString str1;
str1.Format(_T("%d"), index1);
MessageBox(NULL, str1, "testx", MB_OK);
CString's Format works just like printf to populate the string with the parameter list.

Answer 4

The second parameter of MessageBox needs to be a pointer to a string of chars, terminated with NULL. Passing a char will not work.
But, learning to use a debugger is an integral part to learning a language. Why not build a debug build and set a breakpoint on char test1 = index1; instead? You do that by pressing F9 when the cursor is on that line.

Answer 5

For what it's worth, I prefer to use a manipulator for this:
#include <sstream>
#include <iostream>
#include <windows.h>
using std::ostringstream;
using std::ostream;
ostream &msg_box(ostream &s) {
ostringstream &os = dynamic_cast<ostringstream &>(s);
MessageBox(NULL, os.str().c_str(), "testx", MB_OK);
return s;
}
int main() {
ostringstream msg;
msg << "The number is: " << 10 << msg_box;
return 0;
}
This maintains (mostly) the same interface nearly everybody's already accustomed to with iostreams, avoids the type-unsafe CString::Format, and avoids having several lines of distraction everywhere you're going to display a little information for debugging. The other obvious good point is that if you've overloaded operator<< for your own type, that overload will work with this as well.

Answer 6

Acording to your error, you should declare a const pointer on the second parameter.
Like this,
const char * test1= new char();
or use
std::string test1= "";
MessageBox(NULL, test1.c_str(), "testx", MB_OK);
Also using just "Text" will work.

Answer 7

Here is the pure C solution using sprintf method to store all input in buffer and passing that buffer to MessageBox.
#include <stdio.h>
#include <windows.h>
int main(void)
{
int intVal = 50;
float fltVal = 5.5;
char *str = "Test String";
char buf[1024] = {'\0'};//buffer to store formatted input.
//convert formatted input into buffer.
sprintf(buf,"Int value : %d\nFloat value : %f\nString : %s\n",intVal,fltVal,str);
//display whole buffer.
MessageBox(NULL,buf,"INFO",MB_ICONINFORMATION);
return 0;
}