Question

The code below compiles but after clicking on first button it breaks with msg

Unhandled exception at 0x0133ae9a in deming.exe: 0xC0000005: Access violation writing location 0x014aedbd.

Is it a c++ error as i am novice or is it dragonsdk i use ?

//====================================================
// App.cpp
//====================================================
#include "DragonFireSDK.h"
#include <string.h>

int Picture;

int OnClick(int value)
{
    char* image = "Images/image";
    image = strcat(image,"_");
    Picture = PushButtonAdd(image, 10, 100, OnClick, 1);
    return 0;
}

void AppMain()
{
    // Application initialization code goes here.  Create the items / objects / etc.
    // that your app will need while it is running.

    Picture = PushButtonAdd("Images/Logo", 10, 100, OnClick, 1);

}

Answer 1

The reason of your problem is wrong imagination of what strcat does. It is appending second buffer to the first – in this case your first buffer is static, so appending to it obviously fails. You should use something like

char* image = "Images/image";
char* fullname = new char[strlen(image)+2];
strcpy(fullname, image);
strcat(fullname,"_");

Also don’ forget to delete[] fullname after you are done with the buffer.
You might find useful documentation for strcat (and other functions) in here

You migh also consider using C++ std::string, as they do it all for you, and if you need c-style strings, you can always get them via c_str() method.