Edit: I'm trying to tell it to work with C++11 by clicking "Have g++ follow the C++11 ISO C++ language standard" in the compiler flags.
I'm getting stoi was not declared in scope, and I've added c++11 to Code::Blocks; I've added compatibility in Settings -> Compilers -> Compiler flags, but it still keeps giving me that error.
And when I try to do atoi or strtol I get the following error:
C:\Users\user\Desktop\Programming\NewProject\main.cpp|19|error: cannot
convert 'std::string {aka std::basic_string}' to 'const char*'
for argument '1' to 'long int strtol(const char*, char**, int)'|
My code:
#include <iostream>
#include <vector>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;
int main()
{
string numberGuessed;
int numberGuessedint = 0;
do {
cout << "Guess a number between 1 and 10: ";
getline(cin, numberGuessed);
numberGuessedint = stoi(numberGuessed);
cout << numberGuessedint << endl;
} while(numberGuessedint != 4);
cout << "You win!" << endl;
return 0;
}
It is a known bug in MinGW bundled with Code::Blocks.
You can apply a patch: http://tehsausage.com/mingw-to-string
Or download fresh version of MinGW (preferable with threading support, as you lack it too) and replace one you have right now.
To use atoi you need:
numberGuessedint = atoi(numberGuessed.c_str());
I am writing a solution which worked for me. As I found in most of the solutions posted on stack overflow, code blocks earlier versions contain a bug. So I deleted my older code blocks version and installed a new version 17.12 from code blocks website.
Then I just clicked on "Have g++ follow the C++11 ISO C++ language standard" in the compiler flags.
Settings -> Compilers -> Compiler flags.
It works for me(I am using windows 7).
Related
This question already has answers here:
printf with std::string?
(9 answers)
Closed 7 years ago.
I was reading this. That question contains following program.
#include <iostream>
#include <cstdio>
#include <string>
int main()
{
using namespace std;
string myString = "Press ENTER to quit program!";
cout << "Come up and C++ me some time." << endl;
printf("Follow this command: %s", myString);
cin.get();
return 0;
}
I tried it on g++ 4.8.1 & it fails in compilation. g++ 4.8.1 gives following diagnosis.
9 47 [Error] cannot pass objects of non-trivially-copyable type 'std::string {aka class std::basic_string<char>}' through '...'
9 47 [Warning] format '%s' expects argument of type 'char*', but argument 2 has type 'std::string {aka std::basic_string<char>}' [-Wformat=]
What does this error mean? Should this program compile successfully or not? Which compiler is correct (g++ or MSVS 2010) ? Why MSVS 2010 accepts this code? Is the code invokes undefined behavior when compiled on MSVS 2010?
Surprising: I tried it on ideone which uses g++ 5.0 & surprisingly it compiles & runs fine. (See live demo here.). g++ 5.2.0 gives warning when I compile this code. (See live demo here). Why it compiles fine on ideone but fails on g++ 4.8.1? g++ 4.8.2(gives same diagnosis as g++ 4.8.1, 4.9.0,4.9.1,4.9.2 (gives error not warning). g++ 5.1.0 gives warning but program still compiles & runs fine.
Why different versions of g++ behave differently when compiling above program? Is this bug in g++ ? Clang also rejects this code to compile in response to answer given by #TemplateRex
Clang errors out with "error: cannot pass non-trivial object of type 'string' (aka 'basic_string') to variadic function; expected type from format string was 'char *' [-Wnon-pod-varargs]" and suggests the fix "note: did you mean to call the c_str() method?"
#include <iostream>
#include <cstdio>
#include <string>
int main()
{
using namespace std;
string myString = "Press ENTER to quit program!";
cout << "Come up and C++ me some time." << endl;
printf("Follow this command: %s", myString.c_str());
cin.get();
}
and it seems to work.
Here a basic code I'm trying to run But I'm having trouble with stoi (it's c++) I keep getting error:
‘stoi’ was not declared in this scope
I tried atoi and strtol with this error
.cpp:23: error: cannot convert ‘std::string’ to ‘const char*’ for argument ‘1’ to ‘int atoi(const char*)’
The code:
using namespace std;
int main(){
string numberGuessed;
int intNumberGuessed = 0;
do {
cout << "Guess a numeber btw 1 - 10: " << endl;
getline(cin, numberGuessed);
intNumberGuessed = atoi(numberGuessed);
cout << intNumberGuessed << endl;
} while(intNumberGuessed != 4);
cout<< "you win" << endl;
return 0;
}
The atoi() function accepts const char* argument, but you're trying to pass it std::string. Write it like intNumberGuessed = atoi(numberGuessed.c_str()); to take the pointer.
As for the first error, about stoi() being undeclared — it is because the function was added in C++11 standard, so you have to enable its support in your compiler. I.e. in older versions of GCC you could do it with -std=c++11 option (since gcc5 C11 is enabled by default, and since gcc6 C++11 will be enabled by default).
Use stoi, it's the modern C++ version of C's atoi.
Update:
Since the original answer text above the question was amended with the following error message:
‘stoi’ was not declared in this scope
Assuming this error was produced by g++ (which uses that wording), this can have two different causes:
Using a non-conforming variant of g++ that doesn't provide std::stoi.
Using g++ in C++03 mode (stoi was introduced in C++11).
For Windows, the MinGW-w64 variant is known to provide std::stoi, and in particular the Nuwen distribution is based on MinGW-w64.
For C++11 mode, with g++ use the option -std=c++11. For example, this is necessary with the Nuwen distribution g++ version 5.1.
I've got some code that I'm running on Mac OS X that can't be compiled on the Virtual Machine running Linux Mint. This is a simple example. When I run it in Mac, all is fine, but I'm getting issues when I run the same code on Linux, so I'm assuming the library I'm including is not there, but should I be getting an include error then?
Here's the example code that runs on Mac.
#include <iostream>
#include <stdlib.h>
#include <string>
#include <cstdlib>
using namespace std;
int main(){
for (int i = 0; i < 10; i++){
string test = to_string(i);
cout << test << endl;
}
cout << "done" << endl;
return 0;
}
I get no issues here but running on Linux Mint, I get this when I try to compile:
for.cpp: In function 'int main()':
for.cpp:7:28 error: 'to_string' was not declared in this scope
string test = to_string(i);
^
make: *** [for] Error 1
Am I missing something? Any help would be much appreciated!
edit
I realize I forgot to include <string> on here and I fixed it, but what I changed (<string> included) still doesn't compile on Linux. I've used to_string before. I know that much in C++. I also tried adding <cstdlib>. Once again, this DOES compile on Mac and DOES NOT compile on Linux.
Here is my OSX output:
0
1
2
3
4
5
6
7
8
9
done
Here is my output on Linux Mint (Once again, Virtual Box, g++ make):
test.cpp: In function ‘int main()’:
test.cpp:9:28: error: ‘to_string’ was not declared in this scope
string test = to_string(i);
^
make: *** [test] Error 1
You could reproduce the problem yourself if you don't believe me. It's the same code, you can see for yourself if you want.
Compile your for.cpp file like this:
g++ -std=c++11 for.cpp
and run it with:
./a.out
The support for the to_string function in the <string> header was added in the C++11 version of the language, so you need to tell GCC to use that version. You can use the c++0x flag too, for example:
g++ -std=c++0x for.cpp
And you don't have to worry about <cstdlib>, that has nothing to do with it...
to_string() is defined in <string> if you are compiling with C++11 (but is not defined, or unreliably defined as an extension feature, if you are compiling with an earlier version of C++).
Reference: http://en.cppreference.com/w/cpp/string/basic_string/to_string
SOLUTION:
I found a better solution. For some reason, I've read stdlib.h will not work on some linux systems. I used a different function to convert int to string.
on linux:
#include <stdio.h>
and then
for (int i = 0; i < 10; i++){
char buffer[10];
sprintf(buffer,"%d",i);
string stringInt = buffer;
cout << stringInt << endl;
// do whatever you want with the string
}
edit
To the person that down voted my solution to this, here's a post from six years ago basically saying the same thing.
I've been learning C++ and using the Terminal for the last couple of months. My code was compiling and running fine using g++ and C++11, but in the last couple of days it started giving errors and I have had problems compiling since. The only programs I can compile and run depend on older C++ standards.
The errors I first got related to #include < array > in the header file. Not sure why this happened, but I got around it by using boost/array instead. Another error I can't solve is with std::stoi. Both array and stoi should be in the C++11 standard library. I made the following simple code to demonstrate what's going on:
//
// stoi_test.cpp
//
// Created by ecg
//
#include <iostream>
#include <string> // stoi should be in here
int main() {
std::string test = "12345";
int myint = std::stoi(test); // using stoi, specifying in standard library
std::cout << myint << '\n'; // printing the integer
return(0);
}
Try to compile using ecg$ g++ -o stoi_trial stoi_trial.cpp -std=c++11
array.cpp:13:22: error: no member named 'stoi' in namespace 'std'; did you mean
'atoi'?
int myint = std::stoi(test);
~~~~~^~~~
atoi
/usr/include/stdlib.h:149:6: note: 'atoi' declared here
int atoi(const char *);
^
array.cpp:13:27: error: no viable conversion from 'std::string' (aka
'basic_string') to 'const char *'
int myint = std::stoi(test);
^~~~
/usr/include/stdlib.h:149:23: note: passing argument to parameter here
int atoi(const char *);
^
2 errors generated.
I also get these errors at compilation when using gcc or clang++ and with -std=gnu++11 (I guess they all depend on the same file structure). I also get the same error whether I specify std:: in the code, or if I specify using namespace std;
I worry that these issues arose because of the September Command Line Tools update via Xcode or because I installed boost and this somehow messed up my C++11 libraries. Hopefully there is a simple solution.
My system:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-> dir=/usr/include/c++/4.2.1
Apple LLVM version 5.0 (clang-500.2.76) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin12.5.0
Thread model: posix
Thanks for any insight you can offer.
clang has a weird stdlib, you need to add the following flag when you compile
-stdlib=libc++
your snippet works on my mac with
g++ -std=gnu++11 -stdlib=libc++ test.cpp -o test
This answer describes the problem
I am completely new to C++ and I am now following the C++ Primer book.
I wrote a small example about strings, here is the code:
#include <iostream>
#include <string>
#include <cctype>
using std::cin;
using std::cout;
using std::endl;
using std::string;
int main() {
string s("Hello World");
for (auto &c : s)
c = toupper(c);
cout << s << endl;
return 0;
}
I am on Linux with GCC version 4.4.6 and I tried to compile this code with:
g++ test_strings.c -std=c++0x
but got the following errors:
test_strings.c: In function 'int main()':
test_strings.c:14: error: expected initializer before ':' token
test_strings.c:19: error: expected primary-expression before 'return'
test_strings.c:19: error: expected ')' before 'return'
I copied the program from the textbook, so I though it was a misspelling but after a check and trying searching on the web and updating my gcc the error reminds. Help will be greatly appreciated, thanks in advance.
As per the C++0x/C++11 Support in GCC page, you need to be running gcc 4.6 to get the range-for feature.
The 4.6 changes page contains:
Improved experimental support for the upcoming C++0x ISO C++ standard, including support for constexpr (thanks to Gabriel Dos Reis and Jason Merrill), nullptr (thanks to Magnus Fromreide), noexcept, unrestricted unions, range-based for loops (thanks to Rodrigo Rivas Costa), opaque enum declarations (thanks also to Rodrigo), implicitly deleted functions and implicit move constructors.
Since you're running gcc 4.4.6, it's not available to you.