#include <iostream>
int Main();
{
std::cout <<"hello world\n";
return 0;
}
This is simple yet i get "undefined reference to 'winmain#1'" i have tried replacing int main with int winmain. But the same problem still occurs. can use some professional help please. Good vibes please <3
I see two issues here:
Not adhering to proper main method name. It should be main() and not Main()
Misplaced semicolon after int Main(). That terminates the definition and the code that follow is just having a different scope altogether.
If you make these changes, your code should compile successfully.
Related
In the journey to learning C++ im learning through the C++ Manual thats on the actual website. Im using DevC++ and have hit a problem, not knowing whether its the compilers error or not.
I was going through this code bit by bit typing it in myself, as I feel its more productive, and adding my own stuff that ive learnt to the examples, then I get to initialising variables. This is the code that is in the C++ manual
#include <iostream>
using namespace std;
int main ()
{
int a=5; // initial value = 5
int b(2); // initial value = 2
int result; // initial value undetermined
a = a + 3;
result = a - b;
cout << result;
return 0;
}
This is popping up a compiler error saying " Multiple definitions of "Main""
Now This is on the actual C++ page so im guessing its a compiler error.
Could someone please point me in the right direction as to why this is happening and what is the cause for this error.
Multiple definitions of "main" suggests that you have another definition of main. Perhaps in another .c or .cpp file in your project. You can only have one function with the same name and signature (parameter types). Also, main is very special so you can only have one main function that can be used as the entry point (has either no parameters, one int, or an int and a char**) in your project.
P.S. Technically this is a linker error. It's a subtle difference, but basically it's complaining that the linker can't determine which function should be the entry point, because there's more than one definition with the same name.
Found I had two file references in my tasks.json file that were causing this error and which took me a long time to figure out. Hope this helps someone else..... See "HERE*****" below:
"-I/usr/include/glib-2.0",
"-I/usr/lib/x86_64-linux-gnu/glib-2.0/include",
//"${file}", //HERE**********************
"-lgtk-3",
"-lgdk-3",
"-lpangocairo-1.0",
"-lpango-1.0",
"-lharfbuzz",
"-latk-1.0",
"-lcairo-gobject",
"-lcairo",
"-lgdk_pixbuf-2.0",
"-lgio-2.0",
"-lgobject-2.0",
"-lglib-2.0",
"-o",
"${fileDirname}/${fileBasenameNoExtension}" //HERE*************
],
When I practiced CMake, I encountered the same problem. Finally, I found that the source code path set in the cmakelist project was incorrect. As a result, the compiled files included many duplicate files generated during CMake execution. As a result, compilation errors occurred
First my code:
#include <iostream>
#include <thread>
#using <System.dll>
using namespace System;
using namespace System::IO::Ports;
using namespace System::Threading;
int main()
{
SerialPort^ mySerialPort = gcnew SerialPort("COM5");
mySerialPort->BaudRate = 9600;
mySerialPort->Parity = Parity::None;
mySerialPort->StopBits = StopBits::One;
mySerialPort->DataBits = 8;
mySerialPort->Handshake = Handshake::None;
mySerialPort->RtsEnable = true;
while (1)
{
Console::WriteLine(Console::ReadLine());
}
}
The idea was to read from the SerialPort and write to the console. Source
Originally I was going to use:
std::cout << Console::ReadLine() << '\n';
However, that had an error (ReadLine outputs String^ not String, I don't know the difference) and I was hoping for something to compile.
With the above code I received the error:
two-phase name lookup is not supported for C++/CLI ... use /Zc:twoPhase-
The error recommends I use /Zc:twoPhase- which is a compiler option. So I enabled it and got the error:
Element has an invalid value of "Yes(/permissive-) /Zc:twoPhase-"
I'm not quite sure how to proceed from here.
Apologies I'm a beginner and I dove way over my head. Any help would be appreciated!
Note: I included thread, I know this code doesn't use it, but I plan on using it later.
Judging by the "Element has an invalid value of "Yes(/permissive-) /Zc:twoPhase-"" you've put this compiler option where it does not belong. Make sure you know where it should go. E.g. Why do I have warning "C4199 two-phase name lookup is not supported for C++/CLI, C++/CX, or openmp"?
There is no solution. I got an "cannot open file 'MSCOREE.lib'" error. It appears that file no longer exists in Windows and I didn't know how to get ahold of it. So I used the Visual Studio Windows Form App.
Edit: eXCore's comment about the .NET framework solved it.
I have recently heard of compiling C++ code to javascript using emscripten and how, if asmjs optimizations are done, it has the potential of running applications really fast.
I have read several post, tutorial and even heard some very interesting youtube videos. I have also run the hello world example successfully.
However, I don't know the full capabilities of this approach, specially if an entire new webapp can/should be written in C++ as a whole, without glue code.
More concretely I would like to write something similar to the following C++ (as a reference not working code).
#include <window>
class ApplicationLogic : public DOMListener{
private:
int num;
public:
ApplicationLogic():num(0);
virtual void onClickEvent(DOMEventData event){
num++;
}
virtual ~ApplicationLogic(){}
}
int main(){
DOMElement but = Window.getElementById("foo");
ApplicationLogic app();
but.setOnclick(app);
}
I hope it makes clear the idea, but the goal is to achieve something similar to:
A static function that initializes the module run when the window is ready (same behaviour that gives jquery.ready()). So listeners can be added to DOM elements.
A way to interact with the DOM directly from C/C++, hence the #include <window>, basically access to the DOM and other elements like JSON, Navigator and such.
I keep thinking of Lua and how when the lua script includes a shared object (dynamic linked library) it searched for a initialize function in that .so file, and there one would register the functions available from outside the module, just exactly how the return of the function module created in asmjs acts. But I can't figure out how to emulate jquery.ready directly with C++.
As you can see I have little knowledge about asmjs, but I haven't found tutorials or similar for what I'm looking for, I have read references to standard libraries included at compile time for stdlibc, stdlibc++ and SDL, but no reference on how to manipulate the DOM from the C++ source.
what's up. I know this is an old topic, but I'm posting here in case anyone else comes here looking for the answer to this question (like I did).
Technically, yes it is possible - but with a ton of what you called "glue code", and also a good bit of JavaScript (which kind of defeats the purpose IMO). For example:
#include <emscripten.h>
#include <string>
#define DIV 0
#define SPAN 1
#define INPUT 2
// etc. etc. etc. for every element you want to use
// Creates an element of the given type (see #defines above)
// and returns the element's ID
int RegisterElement(int type)
{
return EM_ASM_INT({
var i = 0;
while (document.getElementById(i))
i++;
var t;
if ($0 == 0) t = "div";
else if ($0 == 1) t = "span";
else if ($0 == 2) t = "input";
else
t = "span";
var test = document.createElement(t);
test.id = i;
document.body.appendChild(test);
return i;
}, type);
}
// Calls document.getElementById(ID).innerHTML = text
void SetText(int ID, const char * text)
{
char str[500];
strcpy(str, "document.getElementById('");
char id[1];
sprintf(id, "%d", ID);
strcat(str, id);
strcat(str, "').innerHTML = '");
strcat(str, text);
strcat(str, "';");
emscripten_run_script(str);
}
// And finally we get to our main entry point...
int main()
{
RegisterElement(DIV); // Creates an empty div, just as an example
int test = RegisterElement(SPAN); Creates an empty SPAN, test = its ID
SetText(test, "Testing, 1-2-3"); Set the span's inner HTML
return 0; And we're done
}
I had the same question and came up with this solution, and it compiled and worked as expected. But we're basically building a C/C++ API just to do what JavaScript already does "out of the box". Don't get me wrong - from a language standpoint I'd take C++ over JavaScript any day - but I can't help but think it's not worth the development time and possible performance issues involved in a setup like this. If I were going to do a web app in C++, I would definitely use Cheerp (the new name for Duetto).
As somebody pointed out already, if you start of with a fresh codebase exclusively for the web, then duetto could be a solution. But in my opinion duetto has many drawbacks, like no C allocators, which would probably make it very hard if you want to use 3rd party libraries.
If you are using emscripten, it provides an API for all kinds of DOM events, which does pretty much exactly what you want.
emscripten_set_click_callback(const char *target, void *userData, int useCapture, int (*func)(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData));
hope this helps
Hallo fellow members,
I run into a very strange problem today and I am not exactly sure as to what is causing it. Here is a function which I use to get the current working directory :
#ifdef _WIN32
#include <direct.h>
#define GetCurrentDir _getcwd
#else
#error "There is currently no support for non windows based systems!"
#endif
const std::string getCurrentPath()
{
char CurrentPath{_MAX_PATH];
GetCurrentDir(CurrentPath, _MAX_PATH);
CurrentPath[_MAX_PATH - 1] = '/0';
return std::string(CurrentPath);
}
This function works well as a stand alone function. However if I declare it as a static function inside a class :
static __declspec(dllexport) const std::string getCurrentPath(void);
and a .dll I get "debug assertion failed error" when I try to do
std::cout<<CUtilities::getCurrentPath()<<std::endl;
If I instead write :
std::string dir = CUtilities::getCurrentPath();
std::cout<<"Dir is : "<<dir<<std::endl;
it works fine. I am totally confused as to what I am doing wrong. Any ideas?
I finally found out what the problem was. The project was compiled with /MT options , therefore the .dll had a different heap than the original file. So when the string size was bigger than it's initial size (15) then heap was allocated from the .dll's side. However the string had it's destructor called from the main program side and then the destructor was trying to deallocate memory from the .dll's heap thus resulting in "heap corruption error"
The solution was to simply compile with /MD options.
The following simple program can't be compiled with gcc 4.4.3
#include "rapidxml.hpp"
#include "rapidxml_utils.hpp"
#include "rapidxml_print.hpp"
#include "rapidxml_iterators.hpp"
int main()
{
return 0;
}
Compile produces following errors:
rapidxml_iterators.hpp:21: error: expected nested-name-specifier
rapidxml_iterators.hpp:21: error: invalid declarator before ‘value_type’
rapidxml_iterators.hpp:22: error: expected nested-name-specifier
rapidxml_iterators.hpp:22: error: invalid declarator before ‘&’ token
..........
What I am doing wrong?
These errors are caused by the rapidxml_iterators.hpp header. It seems including this header is not necessary for regular xml parsing. Apparently, the iterators defined in there are not really usable anyway. It might be something still under development. See also here.
The rapidxml_iterators.hpp have some problem with it. You have to change it to this:
typedef xml_node<Ch> value_type;
typedef xml_node<Ch> &reference;
typedef xml_node<Ch> *pointer;
typedef typename std::ptrdiff_t difference_type;
typedef typename std::bidirectional_iterator_tag iterator_category;
Simple solution for simple case
You don't actually need rapidxml_iterators.hpp but were doing a sanity check, right ?
Solution: only #include the headers you actually need.
It's a general rule. #include'ing everything is like eating too much : it turns the situation fat and slow.
By contrast, including only what you need:
keeps you aware of your actual code dependency,
helps keeping you safe from namespace pollution and the occasional name clashes and sometimes even portability issues,
alerts you when you are starting to mess together things that should be kept separated.
If you really need rapidxml_iterators.hpp
At this point, the problem is probably solved. If you really need rapidxml_iterators.hpp, it's indeed buggy (looks like this particular error is a Microsoftism). This problem and others were reported on February 2010 on http://sourceforge.net/p/rapidxml/bugs/10/ with suggested solutions different from #user437634's, still open and present in current release as of July 2013.