Why do i get a warning for creating basic class?

Question

I created this but i am getting linking errors but i don't know why...

SysInfo.h

#include <iostream>

class SysInfo 
{

  public:
    SysInfo();
    ~SysInfo();

  private:

};

SysInfo.cpp

#include "SysInfo.h"

using namespace std;

SysInfo::SysInfo()
{
  cout << "Object is being created" << endl;
} 

SysInfo::~SysInfo()
{
  cout << "Object is being deleted" << endl;
}

Main

#include <tchar.h>
#include "Sysinfo.h" 

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    SysInfo inf;
    getchar();

    return 0;
}

Message

warning C4930: 'SysInfo inf(void)': prototyped function not called (was a variable definition intended?)

The issue is solved. The code you see is corrected code. I changed #include <SysInfo.h> to #include "SysInfo.h" and turned off the pre compile setting in visual studio 2012. That was giving errors ass well.

[Most Vexing Parse](https://en.wikipedia.org/wiki/Most_vexing_parse) Problem? — Dean Seo, Apr 28 '17 at 08:17

score 2 · Accepted Answer · edited May 23 '17 at 11:46

2

SysInfo inf(); is a declaration of function inf, returning SysInfo class.

Should be SysInfo inf;

#include <SysInfo.h> is a possible source of concern too. See this for the additional info.

edited May 23 '17 at 11:46

Community

1
1

answered Apr 28 '17 at 08:13

Ari0nhh

5,720
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then i get luinking error :error LNK2019: unresolved external symbol "public: __thiscall SysInfo::~SysInfo(void)" (??1SysInfo@@QAE@XZ) referenced in function __catch$??0CMainFrame@@QAE@XZ$0 and error LNK2019: unresolved external symbol "public: __thiscall SysInfo::SysInfo(void)" (??0SysInfo@@QAE@XZ) referenced in function __catch$??0CMainFrame@@QAE@XZ$0 – vincent poortvliet Apr 28 '17 at 08:19
Is `SysInfo.cpp` file included in the project? It looks like you are providing only class declaration for the compiler. – Ari0nhh Apr 28 '17 at 08:20
yes SysInfo.cpp is included in the project – vincent poortvliet Apr 28 '17 at 08:22
Then we need a [mcve]. – Ari0nhh Apr 28 '17 at 08:24
@default explane? – vincent poortvliet Apr 28 '17 at 08:24
The code i show is the code i got :) but i fixed it by changing the include from #include to #include "SysInfo.h" and turning off the precompile settings – vincent poortvliet Apr 28 '17 at 09:08

score 1 · Answer 2 · answered Apr 28 '17 at 08:14

1

SysInfo inf(); is a function declaration! A method named inf that takes nothing and returns SysInfo.

Do this to declare object of SysInfo: SysInfo inf;

answered Apr 28 '17 at 08:14

CinCout

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score 0 · Answer 3 · answered Apr 28 '17 at 08:40

0

Because your constructor have not any parameters, so you should replace :

int main()
{
    SysInfo inf;
}

with bellow :

int main()
{
    SysInfo inf();
}

so try with SysInfo inf without ().

answered Apr 28 '17 at 08:40

BattleTested_закалённый в бою

4,037
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There are two answers already explaining exactly this – default Apr 28 '17 at 09:00
@Default because, i had preparing the answer and it takes a little time. – BattleTested_закалённый в бою Apr 28 '17 at 09:03

Why do i get a warning for creating basic class?

3 Answers3