Error with stoi and debugged with gdb

Question

My OS is ubuntu 14.04, laptop, i7.

The g++ version is g++ (Ubuntu 4.8.2-19ubuntu1) 4.8.2.

I tried to run a simple code to test stoi:

#include <string>
int main() 
{
   std::string s = "123";
   int i = std::stoi(s);
}

When I compile it with: g++ -g prueba2.cpp, I get:

prueba2.cpp: In function ‘int main()’:
prueba2.cpp:6:12: error: ‘stoi’ is not a member of ‘std’
    int i = std::stoi(s);
            ^

When I debug it twice first with g++ -std=c++0x -g prueba2.cpp (I also tried with -std=c++11) and then with dbg, I got:

enter image description here

Then, I also did a simple search and followed the suggestions made in here1, here2 and here3, and none worked.

Am I doing something silly?

If the compiler gave you a fatal error, what makes you think it output runnable code? — Mark Ransom, Jun 17 '15 at 20:11
Did it compile if you used `g++ -std=c++11 -g prueba2.cpp`? If not what was the error? — NathanOliver, Jun 17 '15 at 20:15
Your code compiles fine and you got `exited normally` message. So, what is the problem? — Zereges, Jun 17 '15 at 20:16

score 1 · Accepted Answer · answered Jun 17 '15 at 20:40

Yeah, I think you're doing something pretty silly. You probably compiled the first code, which doesn't have the std::cout statement, and you probably executed the compilation steps without -std=c++11 which would result in std::stoi not being included beecause std::stoi is from C++11 and onward. The result is still the old executable which prints out nothing.

Recompile using -std=c++11 and make sure that you saved your file correctly. Your code clearly works.

Note: the vanilla port of GCC of MinGW on Windows is flawed and has a few bugs related to C++11 and onwards; using MinGW-w64, if you ever decide to compile on Windows, can help the problem.

yeap, it works properly like you say – Another.Chemist Jun 17 '15 at 21:47 — Another.Chemist, Jun 17 '15 at 21:47

mastov · Answer 2 · 2015-06-17T20:29:15.893

0

std::stoi is a C++11 feature. Therefore your code only compiles, if you use the -std=c++11 flags (or the equivalent -std=c++0x flag that you mentioned, which has nothing to do with debugging).

The terminal session you provided also shows that compilation works with those flags and your program runs fine without any problem. If you want to print the parsed result, you can do it like that: std::cout << i << std::endl

If you don't want to use C++11 features, you can use the >> stream operator to parse your string to an int:

stringstream ss(s);
int i;
ss >> n;

But beware: Other than with stoi, you won't get an exception, if your input doesn't contain a valid number. You will have to check the stream's status yourself.

edited Jun 17 '15 at 20:29

answered Jun 17 '15 at 20:19

mastov

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ok, understood, it generates the file to gdb. Still, your answer is not a solution. how can I solve the general issue of `stoi`? – Another.Chemist Jun 17 '15 at 20:21
What is the "general issue"? It works fine. Just use it. And if you don't want to compile with C++11, you can use the stream operators to parse your input. – mastov Jun 17 '15 at 20:22
@beginner What is "general issue of `stoi`", There is no issue in your code. – Zereges Jun 17 '15 at 20:22
When I add `std::cout << i << "\n";`, it prints nothing. – Another.Chemist Jun 17 '15 at 20:27
@beginner: Yes, it does: http://cpp.sh/3mfsf – mastov Jun 17 '15 at 20:37

Error with stoi and debugged with gdb

2 Answers2