I am working on a server with GCC version 4.4.7, and I am forced to work with this version unfortunately. I want to make use of the <random> library of C++0x, but I read here that in this version uniform_real_distribution is called uniform_real. When I try to call this function and normal_distribution, I don't get useful output. See this example:
#include <random>
#include <iostream>
using namespace std;
int main()
{
typedef std::mt19937 Engine;
typedef std::uniform_real<double> Dis1;
typedef std::normal_distribution<double> Dis2;
Engine eng(0);
Dis1 dis1(0, 1);
cout << dis1(eng) << endl; //OUTPUTS 3.49921e+09
Dis2 dis2(0, 1);
cout << dis2(eng) << endl; //STALLS, NO OUTPUT
return 0;
}
I compile with g++44 -std=c++0x main.cpp and I have shown what output I get. What is the issue here?
C++11 support in gcc 4.4 is rather sparse.
The release notes for gcc 4.5 include
Improved experimental support for the upcoming ISO C++ standard,
C++0x
specifically mentioning <random>.
Related
I can not find any new c++20 features of std::atomic_flag (Proposal P0995R1)
I looked in gcc status table but did not found anything about it
https://gcc.gnu.org/projects/cxx-status.html
Then i tried compile code below on gcc and clang compilers, but this code compiles only on trunk branch of gcc and clang
#include <atomic>
#include <thread>
int main()
{
std::atomic_flag f;
std::thread t([&]
{
f.wait(false);
std::cout << "gggg" << std::endl;
});
using namespace std::chrono_literals;
std::this_thread::sleep_for(3s);
f.test_and_set();
f.notify_all();
t.join();
std::cout << "Hello World!\n";
}
Does anyone know about implementation status of this features?
This kind of latest feature heavily depends on the compiler.
Use boost::atomic_flag. it is original and compiler/os independent
I am setting up my MacBook for C++20 and having problem to compile the code. I have installed latest Xcode, llvm and gcc. Here is the code that I am trying to compile
#include <chrono>
#include <experimental/coroutine>
#include <future>
#include <iostream>
using namespace std;
generator<int> getInts(int first, int last) {
for (auto i = first; i <= last; ++i) {
co_yield i;
}
}
int main() {
for (auto i : getInts(5, 10)) {
std::cout << i << " ";
}
}
however I am getting following error:
$ g++ gen.cpp -std=c++2a
In file included from gen.cpp:2:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/experimental/coroutine:66:5: warning:
<experimental/coroutine> cannot be used with this compiler [-W#warnings]
# warning <experimental/coroutine> cannot be used with this compiler
^
appreciate any insight how to resolve this compile issue.
The Coroutines TS has not been voted into C++20 (indeed, there have been three separate votes, with approval not achieving consensus in all of them), so even if GCC implemented it (which it doesn't), it wouldn't be activated by the -std=c++2a switch.
Now, Clang does implement the Coroutines TS, which you have to turn on with -fcoroutines-ts. And apparently, you have to be using libc++.
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.
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.
C++ returns invalid value in the following code:
#include <iostream>
#include <vector>
using namespace std;
int f(){
vector< int * > v[2];
return 1;
v[1].push_back(NULL);
}
int main(){
cout << f();
}
The output is:
205960
When I commnet line after return, it works fine:
#include <iostream>
#include <vector>
using namespace std;
int f(){
vector< int * > v[2];
return 1;
//v[1].push_back(NULL);
}
int main(){
cout << f();
}
The output is:
1
I am using code::blocks with mingw32-g++.exe compiler. The mingw version is: gcc version 4.4.1 (TDM-2 mingw32).
Your compiler has a bug. Fortunately, it is also obsolete. You should upgrade — G++ is up to version 4.6.2, which also implements much of C++11, which is very useful.
If you choose to stick with an older compiler, that is also a decision to accept its flaws.
Edit: If you are really stuck with 4.4 (for example due to a PHB), that series is still maintained. You can upgrade to GCC 4.4.6, released just this past April.