Visual Studio doesn't recognize std library

Question

I'm writing an MFC application on Visual Studio 2015 in C++. I added some code which uses members of std library and suppose to take an int and create from it a hex char* with the prefix "0x". I tried to build the project on VS 2015 and VS 2017 from two different computers and I get the same errors - VS doesn't recognize the std library. I've tied running the code on other programs (Clion) and it worked well.

When I include #include <stdlib> I get the following error: cannot open source file "stdlib"

I've tried re-installing VS, and checked I have all the necessary extensions to support C++, but I guess there's still something missing. How can I fix it?

The code:

std::ostringstream ss;
int i = 7;

ss << std::hex << std::showbase << i;
std::string str = ss.str();
const char *output = str.c_str();

std::cout << output << std::endl;

and included the following headers:

#include <iostream>
#include <sstream>
#include <iomanip>
#include <string>
#include <strstream>

I get the following errors:

'Ostringstream': is not a member of 'std'
'Ostringstream': undeclared identifier
'ss': undeclared identifier
'hex': is not a member of 'std'
'showbase': is not a member of 'std'
'string': is not a member of 'std'
'string': undeclared identifier

Thank you.

C++ is case sensitive `Ostringstream` should be `ostringstream` — Alan Birtles, Aug 25 '20 at 07:27
@george `stdlib.h` is a c header, `cstdlib` is for c++, `stdlib` doesn't exist in either — Alan Birtles, Aug 25 '20 at 07:29
If Visual Studio had such problems, people would have realized it 20 years ago. Errors like these occur when a project's include and library paths are wrong. How did you create that project? Have you tried creating a *new* project and compiling it? Just a simple console app would do. — Panagiotis Kanavos, Aug 25 '20 at 07:30
@AlanBirtles In my code I've used `ostringstream` with small letter — user14092875, Aug 25 '20 at 07:42
@Bathsheba you're right, when I open new console app project, I can't even run simple 'Hello world' program. what can cause it? — user14092875, Aug 25 '20 at 07:43
@user14092875: Can you replace your example code with the "Hello world!" program? — Bathsheba, Aug 25 '20 at 07:44
@Bathsheba I've tried to reproduce the error - but the second time I've built it and pressed on run it worked. I'm sorry for the misunderstanding. . — user14092875, Aug 25 '20 at 08:38
@AlanBritles, you're right but I've checked my code again (and you can also see in the code lines I've added) and ostringstream is written in small letters. — user14092875, Aug 25 '20 at 08:40

score 1 · Accepted Answer · answered Aug 26 '20 at 06:16

I've included the headers in the wrong order. In every C++ project in Visual Studio it includes "stdafx.h" library automatically. This library contains many of the commonly used libraries such as <string> and etc. The solution was to write the includes in the following way:

#include "stdafx.h"
// other headers of the form "header.h"

#include <cstdlib>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <string>
#include <strstream>
// other headers of the form <header>

instead of:

#include <cstdlib>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <string>
#include <strstream>
// other headers of the form <header>

#include "stdafx.h"
// other headers of the form "header.h"

a bit more about this in this question

Thanks for everyone who tried to help, I appreciate your time and attention.

I am glad you have got your solution and thanks for your sharing, I would appreciate it if you mark them as answer and this will be beneficial to other community. — Barrnet Chou, Aug 26 '20 at 07:40
@BarrnetChou I will make sure to mark it as an answer as soon as I will be able to. unfortunately, for some reason (perhaps because I'm new) I can mark it as an answer only 24 hours after I've published it. — user14092875, Aug 26 '20 at 08:31

Visual Studio doesn't recognize std library

1 Answers1