.cpp file
#include "StdAfx.h"
#include "LinkX.h"
#include<iostream>
#include<string.h>
using namespace std;
LinkX::LinkX(int pid,char *pname)
{
id=pid;
strcpy(name,pname);
next=null;
}
void LinkX::displayLink()
{
cout<<id<<endl;
cout<<name<<endl;
}
the above code gets the error :
Error 3 error C2511: 'LinkX::LinkX(int,char *)' : overloaded member
function not found in 'LinkX'
private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e) {
LinkX *L1=new LinkX(10,"Charvi");
LinkX *L2=new LinkX(20,"Vin");
L1->next=L2;
delete L1;
delete L2;
}
};
This code gets the errors:
Error 1 :error C2664: 'LinkX::LinkX(int,char)' : cannot convert
parameter 2 from 'const char [7]' to 'char' Error 2 :error C2664:
'LinkX::LinkX(int,char)' : cannot convert parameter 2 from 'const char
[4]' to 'char'
What do these errors mean ?
How can I correct them?
These codes were written in visual studio.
Concerning the first error,
Did you declare the LinkX::LinkX(int pid,char *pname) constructor in the class declaration (in your LinkX.h file)?
Concerning the second error:
Your constructor ask for a char* variable, indicating that it needs to modify it.
When you call it, you use constant char arrays, that cannot be modified.
Has your constructor does not realy need to modify the pname variable, you only have change the pname type to const char* and it will be ok.
Related
I am trying to create a function func that returns an std::tuple of an std::unique_ptr<A> and a double. However, when I try to create the tuple I receive errors. The code follows:
#include <tuple>
#include <memory>
class A {
public:
A() : data (3){}
private:
double data;
};
std::tuple<std::unique_ptr<A>, double> func(double num) {
std::unique_ptr<A> a = std::make_unique<A>();
std::tuple<std::unique_ptr<A>, double> temp = std::make_tuple(a, num); // ERROR MESSAGE C
return temp;
}
int main() {
return 0;
}
This code produces the following 4 errors in Visual Studio.
Error message A:
tuple(827,18): error C2440: '<function-style-cast>': cannot convert from 'initializer list' to '_Ttype'
Error message B:
tuple(825,83): message : No constructor could take the source type, or constructor overload resolution was ambiguous
Error message C:
Source.cpp(14): message : see reference to function template instantiation 'std::tuple<std::unique_ptr<A,std::default_delete<A>>,double> std::make_tuple<std::unique_ptr<A,std::default_delete<A>>&,double&>(std::unique_ptr<A,std::default_delete<A>> &,double &)' being compiled
Error message D:
tuple(827,12): error C2064: term does not evaluate to a function taking 2 arguments
First, what is the cause of this error? Second, is the A associated with a being placed on the heap?
A std::unique_ptr is not copyable. You are attempting to copy a std::unique_ptr to the tuple, and that will not work. The compiler error message is kind of cryptic, IMO, but that is basically what seems to be the problem.
However, a std::unique_ptr is moveable, thus you can use std::move:
std::tuple<std::unique_ptr<A>, double> temp = std::make_tuple(std::move(a), num);
I am trying to use the function gluTessCallback but I get C2440 error. I have no idea why.
Here is the code:
#define callback void(CALLBACK*)()
template<typename T>
class Tessellation
{
private:
GLUtesselator *pTess;
void CALLBACK tessError(GLenum error)
{
sendErrorMessage((char *)gluErrorString(error), true);
}
public:
void Triangulation3D(T* & point, short numOfPoints)
{
pTess = gluNewTess();
gluTessCallback(pTess, GLU_TESS_ERROR, (callback)tessError);
}
};
The error is on gluTessCallback function:
error C2440: 'type cast' : cannot convert from 'overloaded-function' to 'void (__stdcall *)(void)'
Why do I get this compile error?
The error id C2440 on Visual Studio is a type conversion error.
The problem in your code is that you are trying to pass a class method Tessellation::tessError() as function pointer to gluTessCallback(), which expects a pointer to a global C-style function.
A class method is very different from a free/global function and you cannot pass it as a simple function pointer because it needs an object to go along with it every time, the this pointer.
A solution to your problem would be to declare tessError() as a static method, making it effectively the same as a free/global function scoped inside the class, like so:
template<typename T>
class Tessellation
{
private:
static void CALLBACK tessError(GLenum error)
{
sendErrorMessage((char *)gluErrorString(error), true);
}
...
And pass it to gluTessCallback():
gluTessCallback(pTess, GLU_TESS_ERROR, (callback)&Tessellation<T>::tessError);
The only downside to this approach is that a static tessError() can no longer access class variables. Which doesn't seem like a problem to you, since it is not doing so right now, it appears.
template<class CharType>
struct MyString
{
MyString()
{}
MyString(CharType*)
{}
};
int main()
{
char* narrow_str = 0;
MyString<char>(narrow_str); // error C2040
}
My compiler is VC++ 2013 RC.
The simplest code cannot be compiled because of the error C2040.
error C2040: 'narrow_str' : 'MyString' differs in levels of
indirection from 'char *'
Why?
The problem is this is actually not being parsed as a constructor call but as a variable definition. The problem is you already defined a variable narrow_str. You may have already known this but you can easily fix this by giving it a name.
template<class CharType>
struct MyString
{
MyString()
{}
MyString(CharType*)
{}
};
int main()
{
char* narrow_str = 0;
MyString<char> ns(narrow_str); // error C2040
}
BTW this is also the source of the most vexing parse which occurs when this type of syntax is used in a function argument.
To be honest though I'm surprised that you got a different error because both g++ and clang gave me a clear error.
your syntax in creating a struct is wrong .
change
MyString<char>(narrow_str); // error C2040
to
MyString<char> myString(narrow_str);
will be ok.
I have made a test case to show the problems I am running into. Please forgive me my ignorance on the issues of Deferred libraries and pointer casting. The only library included in the deferred.lib.
#include <deferred/deferred.h>
using namespace deferred;
SafePtr<Deferred> recordTime(int time)
{
SafePtr<Deferred> d = createDeferred();
SafePtr<CallbackData> p = new PointerCBD< char>( 0 );
d->execute(p);
return d;
}
int main(int argc, char* argv[])
{
while(1)
{
SafePtr<Deferred> d = recordTime(1000);
d->waitHereForCompletion();
char* c = dynamic_pointer_cast<char>(d->endResult());
}
return 0;
}
When I try and compile in Windows XP with VS2008 I get:
Error C2440: 'initializing' : cannot convert from
'deferred:SafePtr' to 'char *' with
[T=char]
No user-defined-conversion operator available that can perform this
conversion, or the operator cannot be called.
I have tried this command to return a pointer, rather than a SafePtr:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult()).get();
Then I get this error:
Error C2664: 'deferred::intrusive_ptr_release' : cannot convert
parameter 1 from 'char *' to
'deferred:ReferenceCountable *'
I have tried this command:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult().get());
Then I get this error:
Error C2784: 'deferred::SafePtr deferred::dynamic_pointer_cast(const deferred::SafePtr< U > &)' : could not deduce template argument for 'const deferred::SafePtr< U > &' from 'deferred::CallbackData *'
Try this:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult().get());
if you want to get an "unsafe" pointer, or probably this:
SafePtr<ManagerTimings> t= dynamic_pointer_cast<ManagerTimings>(d->endResult());
to get a safe ManagerTimings pointer. I don't know what library you are using, but I suspect that dynamic_pointer_cast can convert a SafePtr to another SafePtr. Or it just converts pointers.
&*d->endResult()
I think from this code endResult is the SafePtr you're having trouble with.
I am having a problem with command line parsing with boost:program_options. The quickest way to explain it is to show the code so:
const std::vector<tstring> args;
if (ac > 0 && NULL!=av) //ac is a ULONG
{
for (int i = 0; i < ac; i++)
{
args.push_back(av[i]); //av is an LPTSTR pointer (pointer to TCHAR*)
}
}
po::command_line_parser parser(args);
The parser ctor is supposed to take a const std::vector<charT>
typedef basic_command_line_parser<char> command_line_parser;
typedef basic_command_line_parser<wchar_t> wcommand_line_parser;
/** Creates instance of 'command_line_parser', passes parameters to it,
and returns the result of calling the 'run' method.
*/
template<class charT>
class basic_command_line_parser : private detail::cmdline {
public:
/** Creates a command line parser for the specified arguments
list. The 'args' parameter should not include program name.
*/
basic_command_line_parser(const std::vector<
std::basic_string<charT> >& args);
tstring in my program is
typedef std::basic_string<TCHAR> tstring;
The error I get is:
Error 16 error C2664: 'boost::program_options::basic_command_line_parser<charT>::basic_command_line_parser(const std::vector<_Ty> &)' : cannot convert parameter 1 from 'const std::vector<_Ty>' to 'const std::vector<_Ty> &' myfile.cpp 329
Where, oh where, am I going astray? I've tried all kinds of casting and re-defining, but nothing has worked and I'm at the end of my tether.
Edit #Zac:
Making the changes you suggested... I get the error:
Error 14 error C2664: boost::program_options::basic_command_line_parser<charT>::basic_command_line_parser(const std::vector<_Ty> &)' : cannot convert parameter 1 from 'std::vector<_Ty>' to 'const std::vector<_Ty> &' MyFile.cpp 328
Edit
Just to point out that I am using Visual Studio 2008 VC9 compiler
You seem to be using a unicode build, so either explicitly use the wide char version:
po::wcommand_line_parser parser(args);
or the more flexible:
po::basic_command_line_parser<TCHAR> parser(args);
The line you went astray with is below:
const std::vector<tstring> args;
Change it to:
std::vector<tstring> args;