Including <string>, Use of incomplete type 'std::string'

Question

In this example code, <fstream> works fine but <string> doesn't: (errors in comments)

#include <iostream>
#include <fstream>
#include <string>

int main(){
    using namespace std;
    string line; //incomplete type is not allowed
    ifstream ifile("test.in");
    if(ifile.is_open()){
        while(ifile.good()){
            getline(ifile,line); //identifier "getline" is undefined
        }
    }
}

The error of getline() becomes "namespace "std" has no member "getline"" when I change the code to:

int main(){
    std::string line; //incomplete type is not allowed
    std::ifstream ifile("test.in");
    if(ifile.is_open()){
        while(ifile.good()){
            std::getline(ifile,line); //namespace "std" has no member "getline"
        }
    }
}

This code "fixes" the error of the declaration of string line:

std::string* line;

or also:

using namespace std;
string* line;

Cannot reproduce with c++11; live link: godbolt.org/g/1kpcsJ — Richard Critten
– Richard Critten, Commented Aug 11, 2018 at 13:58
Can't reproduce. What's your compiler and OS, and what command are you using to compile it? — Silvio Mayolo
– Silvio Mayolo, Commented Aug 11, 2018 at 13:58
@HansPassant — standard library headers are supposed to be self-contained. They can be included in any order. — Pete Becker
– Pete Becker, Commented Aug 11, 2018 at 14:02
Is there a precompiled header, such as stdafx.h in your code somewhere? — user7860670
– user7860670, Commented Aug 11, 2018 at 14:06

Michael Veksler · Accepted Answer · 2018-08-11 19:30:19Z

1

I had a similar thing twice. It is very easy to accidentally create an empty "vector", "set", "map", etc files in your project, especially if you accidentally paste source code to your terminal (luckily we include <string> and not >string< ).

Visual c++ will gladly use the empty header instead of the standard one, without giving a single warning. Scan your solution directory for a file named vector.

If that does not help, visual studio has a debugging mode that shows all included files.

If this is gcc or clang, you can run the compiler with -E flag, instead of -c. This will create a text file with all included text in one file (or on stdout). This will give you a hint what is going on. This is how I found my empty "set" file.

answered Aug 11, 2018 at 19:30

Michael Veksler

8,5101 gold badge24 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Soifam · Accepted Answer · 2018-08-12 15:25:17Z

1

Thanks you all for your help. I solved the problem, but I still doesn't know what was its cause. I don't know if it was the configuration of the compiler (probably not because other headers were working fine). I don't think the compiler was broken, beacuse after reinstalling it the problem persisted.

The issue was magically solved after reinstalling the whole Visual Studio Code and completley reconfiguring the compilerand build options.

answered Aug 12, 2018 at 15:25

Soifam

511 silver badge4 bronze badges

Collectives™ on Stack Overflow

Including <string>, Use of incomplete type 'std::string'

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related