I don't want to use -std=c++11.
Is there another way ?
I have this peace of code:
#include <iostream>
using namespace std;
#include <string>
#include <sstream>
int main()
{
std::string str1 = "45";
int myint1 = std::stoi(str1); <--error: Function 'stoi' could not be resolved
}
stoi is from C++11, so if you don't want to use flag -std=c++11 you cannot use stoi (or you can wait until gcc 6.0 will be released, where -std=gnu++14 will be default standard).
But you can use something else: boost::lexical_cast, some manually written function, etc.
If you question is "Can I use stoi with GCC 4.4.7 compiler?", then
Yes, you can use std::stoi with -std=c++0x. GCC 4.4 does not have much of support for fancy C++11 features, but it does support simple C++11 functions like std::stoi. Check this support table out for GCC 4.4's support for C++0x.
Related
I am trying to take a string and parse it into an int. I have read the many answers out there, and it seems that using stoi is the most up-to-date way. It appears to me that stoi uses std, but I am getting Function 'stoi' could not be resolved despitre using namespace std;
#include <iostream>
#include <string>
#include <cstring>
#include <fstream>
#include<stdlib.h>
using namespace std;
int main(int argc, char* argv[]) {
string line = "";
string five = "5";
int number = stoi(five); //Error here with stoi
return 0;
}
Any ideas what is causing this?
Update:
I am using Eclipse. My flags are: -c -fmessage-length=0 -std=c++11
If you are using GCC or MINGW, then this is the answer:
std::stoi doesn't exist in g++ 4.6.1 on MinGW
This is a result of a non-standard declaration of vswprintf on
Windows. The GNU Standard Library defines
_GLIBCXX_HAVE_BROKEN_VSWPRINTF on this platform, which in turn disables the conversion functions you're attempting to use. You can
read more about this issue and macro here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37522.
If you're willing to modify the header files distributed with MinGW,
you may be able to work around this by removing the
!defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF) macro on line 2754 of
.../lib/gcc/mingw32/4.6.1/include/c++/bits/basic_string.h, and adding
it back around lines 2905 to 2965 (the lines that reference
std::vswprintf). You won't be able to use the std::to_wstring
functions, but many of the other conversion functions should be
available.
Please always provide platform and compiler information.
Toggle on C++11 support in your compiler flags. -std=c++11 for a recent gcc. For Eclipse, please refer to the corresponding question in the FAQ and this answer explains how to get rid of the remaining Eclipse warning.
If you are amenable to parsing an int another way, how about using an STL algorithm and a C++11 lambda expression?
#include <algorithm>
#include <iostream>
#include <string>
using namespace std;
int main() {
string str = "12345";
int num = 0;
for_each(str.begin(), str.end(), [&num](char c){ num = 10 * num + (c - '0'); });
cout << str << " = " << num << endl;
}
I am trying to do some very fast conversions in C++ and charconv seems the way to go since it uses a very low level logic. The problem is that when I try to include this header and then call, say, std::to_chars(...), neither the header is found nor std has a 'to_chars' member. I updated and reinstalled gcc but this problem is still there. Now I have seen some threads that say that I should update somehow libc++17 but they are not very specific about what I should do, as things are a bit different for MacOS.
Some code to illustrate the library and it's use:
#include <iostream>
#include <typeinfo>
#include <charconv> //error: 'charconv' file not found
struct to_chars_result{
char *str;
std::errc err;
};
int main(int argc, const char * argv[]) {
std::string str("12Test");
auto result = std::to_chars(str.data(), str.data()+str.size(), 12345); //No
//member named 'to_chars' in namespace 'std'.
return 0;
}
As for gcc -v command output:
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-apple-darwin14.4.0/5.1.0/lto-
wrapper
Ziel: x86_64-apple-darwin14.4.0
Konfiguriert mit: ../gcc-5.1.0/configure --enable-languages=c++,fortran
Thread-Modell: posix
gcc-Version 5.1.0 (GCC)
Any help appreciated!
gcc 5.1 was released on April 22, 2015.
The paper that added to_chars to the C++17 standard was written in 2016.
Why do you expect that gcc5 will have implemented it?
[ Later: That was the paper that added the <charconv> header, too ]
I'm trying to compile an easy program that use the alias declaration.
This is the code:
#include <iostream>
using namespace std;
using in = int;
in main ()
{
in a = 1;
cout << a << '\n';
return 0;
}
The command I use to compile is g++ -std=c++0x program_name.cxx, using the built-in terminal in Kate on Ubuntu OS.
But it doesn't work! Any suggestion?
(instead using typedef int in; it works).
Compile in C++11 mode. Type aliasing is supported only in C++11. I suspect the g++ version that use is older and doesn't fully support c++11, hence fails with c++0x.
Compile with: g++ -std=c++11 file.cpp
and it works.
By the way, it seems to be a terrible idea to alias int in such a way.
I am trying to take a string and parse it into an int. I have read the many answers out there, and it seems that using stoi is the most up-to-date way. It appears to me that stoi uses std, but I am getting Function 'stoi' could not be resolved despitre using namespace std;
#include <iostream>
#include <string>
#include <cstring>
#include <fstream>
#include<stdlib.h>
using namespace std;
int main(int argc, char* argv[]) {
string line = "";
string five = "5";
int number = stoi(five); //Error here with stoi
return 0;
}
Any ideas what is causing this?
Update:
I am using Eclipse. My flags are: -c -fmessage-length=0 -std=c++11
If you are using GCC or MINGW, then this is the answer:
std::stoi doesn't exist in g++ 4.6.1 on MinGW
This is a result of a non-standard declaration of vswprintf on
Windows. The GNU Standard Library defines
_GLIBCXX_HAVE_BROKEN_VSWPRINTF on this platform, which in turn disables the conversion functions you're attempting to use. You can
read more about this issue and macro here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37522.
If you're willing to modify the header files distributed with MinGW,
you may be able to work around this by removing the
!defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF) macro on line 2754 of
.../lib/gcc/mingw32/4.6.1/include/c++/bits/basic_string.h, and adding
it back around lines 2905 to 2965 (the lines that reference
std::vswprintf). You won't be able to use the std::to_wstring
functions, but many of the other conversion functions should be
available.
Please always provide platform and compiler information.
Toggle on C++11 support in your compiler flags. -std=c++11 for a recent gcc. For Eclipse, please refer to the corresponding question in the FAQ and this answer explains how to get rid of the remaining Eclipse warning.
If you are amenable to parsing an int another way, how about using an STL algorithm and a C++11 lambda expression?
#include <algorithm>
#include <iostream>
#include <string>
using namespace std;
int main() {
string str = "12345";
int num = 0;
for_each(str.begin(), str.end(), [&num](char c){ num = 10 * num + (c - '0'); });
cout << str << " = " << num << endl;
}
The regex_search function isn't quite behaving as expected.
#include <iostream>
#include <regex>
#include <string>
using namespace std;
int main()
{
string str = "Hello world";
const regex rx("Hello");
cout << regex_search(str.begin(), str.end(), rx) << endl;
return 0;
}
The output is
0
What's going on?
As pointed out in comments to the question, older implementations of the C++ standard libraries did not yet support all features in C++11. Of course, libc++ being an exception because it was originally built specifically for C++11.
According to this bug report support for <regex> in libstdc++ was only implemented for version 4.9 of GCC. You can check the current status on the libstdc++ status page.
One can confirm, that your example works with GCC 4.9 while still failing with GCC 4.8.