'stoi' was not declared in this scope after using -std=c++11

Question

Most probably this is weird, but when I got this error that stoi wasn't declared in this scope, I smiled because I am familiar with this error and it's solution.

I checked this option have g++ follow the c++11 ISO c++ language standard [-std=c++11] in compiler settings of Code Blocks (16.01, with MinGW) and tried recompiling it, but surprisingly it didn't work and the same error persisted. I tried re-installing CodeBlocks but that didn't work.

Also, I tried with windows power shell and command prompt with g++ math_handler.cpp -std=c++11 but got the same error.

What am I doing wrong?

the code is here:

#include<string>

using namespace std;

int main()
{
    string body="456";
    int i=stoi(body);
}

Note:

I tried with -std=c++0x and g++ too.
the same problem with to_string() function.
gcc version 4.9.2 (tdm -1)

Run `g++ -v` from the command line. Keep an eye out for the version number. If it's below 4.8 c++11 support is iffy. Also make sure you've included ``. Beyond that, not much we can do without seeing your code. — user4581301, Dec 01 '17 at 06:01
More than enough. try `g++ math_handler.cpp -std=c++11` to make sure you are compiling for C++ and if that fails add a [mcve]. — user4581301, Dec 01 '17 at 06:09
@NikosC. yeah, sure. have a look at my code, I added the code. — Muzib, Dec 01 '17 at 06:15
Nearly identical to the test case I threw together. The only way I can get it to fail is if I compiler it as C with gcc instead of g++. — user4581301, Dec 01 '17 at 06:16
Well, you seem to have found a mingw bug then. Use `std::stoi`, outlined in the answer below. Does that work? — Nikos C., Dec 01 '17 at 06:16
@NikosC. No, I tried that too, but compiler says 'stoi isn't part of std' — Muzib, Dec 01 '17 at 06:18
There we go. I am being stupid. Left out the `-std=c++11` No longer confirmed. — user4581301, Dec 01 '17 at 06:28

Muzib · Accepted Answer · 2017-12-22T05:12:55.740

Okay, I found that it is a known bug in MinGW bundled with CodeBlocks. I found the solution here.

Download mingw-to-string-gcc47.zip which contains three patched header files. (Original patches: wchar.h, stdio.h, os_defines.h)

Copy wchar.h and stdio.h from the include directory in the zip file to the following directory (overwrite): C:\mingw\include (replace C:\mingw\ with the appropriate directory)

Copy os_defines.h to the following directory (overwrite): C:\mingw\lib\gcc\mingw32\4.7.0\include\c++\mingw32\bits (replace C:\mingw\ with the appropriate directory) (replace 4.7.0 with the correct version number)

score 0 · Answer 2 · answered Dec 01 '17 at 06:06

0

Did you include the required header file? #include <string>

stoi is also in the std namespace so:

std::stoi()

or:

using namespace std;

answered Dec 01 '17 at 06:06

Alexander Ivanov

366
4
9

@MDMuziburRahman And what is the error message you get when using `std::stoi`? – Nikos C. Dec 01 '17 at 06:17
Check out https://stackoverflow.com/questions/38034197/compile-error-stoi-is-not-a-member-of-std – Alexander Ivanov Dec 01 '17 at 06:59
No, don't recommend `using namespace std;`, Read here: https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice. – Fantastic Mr Fox Dec 22 '17 at 04:05

'stoi' was not declared in this scope after using -std=c++11

2 Answers2