I have been trying to pass arguments to a thread function but haven't been able to. I tried reading about it (Passing multiple arguments to a threaded function) but I still couldn't figure it out. Here is my code:
#include <iostream>
#include <thread>
using namespace std;
void func(int t)
{
cout << t << endl;
}
int main()
{
thread t1(func,4);
t1.join();
return 0;
}
I ran it in the command line (I use zsh incase that matters) by doing this:
g++ test.cpp
./a.out
but I got these errors:
thread_test.cpp:14:12: error: no matching constructor for initialization of 'std::__1::thread'
thread t1(func,4);
^ ~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:379:9: note: candidate constructor template not viable: requires single argument '__f', but
2 arguments were provided
thread::thread(_Fp __f)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:268:5: note: candidate constructor not viable: requires 1 argument, but 2 were provided
thread(const thread&);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:275:5: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
thread() _NOEXCEPT : __t_(0) {}
^
1 error generated.
in case this is important I am using a mac with OSX 10.11.4
Also, to see what versions of c++ I was compiling with I ran this command and got this out put:
g++ --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/c++/4.2.1
Apple LLVM version 7.3.0 (clang-703.0.31)
Target: x86_64-apple-darwin15.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
Pass -std=c++11 and it will work; see my transcript below. (Running on OS X.)
nathanst% g++ t.cpp
t.cpp:13:12: error: no matching constructor for initialization of 'std::__1::thread'
thread t1(func,4);
^ ~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:379:9: note: candidate constructor template not viable: requires single argument '__f', but 2 arguments were
provided
thread::thread(_Fp __f)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:268:5: note: candidate constructor not viable: requires 1 argument, but 2 were provided
thread(const thread&);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/thread:275:5: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
thread() _NOEXCEPT : __t_(0) {}
^
1 error generated.
nathanst% g++ -std=c++11 t.cpp
Related
I'm using Clang 14 (on Apple M1), which has full support for C++ 17, and I'm trying to utilize the new to_chars function. Here's my very simple test file:
#include <charconv>
#include <iostream>
int main() {
char a[10];
double pi = 3.141592;
std::to_chars_result res = std::to_chars(a, a+10, pi);
*res.ptr = '\0';
std::cout << a << std::endl;
}
My compile command is clang -std=c++17 test_to_chars.cpp, and the output is below:
test_to_chars.cpp:8:30: error: call to deleted function 'to_chars'
std::to_chars_result res = std::to_chars(a, a+10, pi);
^~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/charconv:166:6: note: candidate function has been explicitly deleted
void to_chars(char*, char*, bool, int = 10) = delete;
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/charconv:450:1: note: candidate template ignored: requirement 'is_integral<double>::value' was not satisfied [with _Tp = double]
to_chars(char* __first, char* __last, _Tp __value)
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/charconv:458:1: note: candidate function template not viable: requires 4 arguments, but 3 were provided
to_chars(char* __first, char* __last, _Tp __value, int __base)
^
test_to_chars.cpp:8:24: error: no viable conversion from 'void' to 'std::to_chars_result'
std::to_chars_result res = std::to_chars(a, a+10, pi);
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/charconv:154:25: note: candidate constructor (the implicit copy constructor) not viable: cannot convert argument of incomplete type 'void' to 'const std::to_chars_result &' for 1st argument
struct _LIBCPP_TYPE_VIS to_chars_result
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/charconv:154:25: note: candidate constructor (the implicit move constructor) not viable: cannot convert argument of incomplete type 'void' to 'std::to_chars_result &&' for 1st argument
2 errors generated.
I'm calling to_chars(char*, char*, double) but for some reason it's using an implicit conversion and trying to call to_chars(char*, char*, bool, int = 10) instead, which is a deleted function.
Is there a way for me to tell C++ that I don't want it to convert my double parameter to a bool?
I'm using Clang 14 (on Apple M1), which has full support for C++ 17
This is unfortunately not correct. While the compiler itself has full C++17 support, the stdlib of your clang version (Apple clang 14) does not implement any floating point charconv features.
See the entry "Elementary string conversions" in the cppreference table.
It is important to note that you are not running "clang 14", but "Apple clang 14". Your code snippet compiles just fine on normal clang 14.
The code :
#include <bits/stdc++.h>
using namespace std;
int main()
{
cout << "this file works";
return 0;
}
Compiler output was ridiculously long. Some 114000 characters long. This is only a portion of it.
Compiler output on compilation :
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:174:5: note: no known conversion for argument 1 from 'std::basic_string_view<wchar_t>' to 'std::filesystem::__cxx11::path::string_type&&' {aka 'std::__cxx11::basic_string<wchar_t>&&'}
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:167:5: note: candidate: 'std::filesystem::__cxx11::path::path(std::filesystem::__cxx11::path&&)'
path(path&& __p) noexcept
^~~~
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:167:5: note: no known conversion for argument 1 from 'std::basic_string_view<wchar_t>' to 'std::filesystem::__cxx11::path&&'
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:165:5: note: candidate: 'std::filesystem::__cxx11::path::path(const std::filesystem::__cxx11::path&)'
path(const path& __p) = default;
^~~~
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:165:5: note: no known conversion for argument 1 from 'std::basic_string_view<wchar_t>' to 'const std::filesystem::__cxx11::path&'
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:163:5: note: candidate: 'std::filesystem::__cxx11::path::path()'
path() noexcept { }
^~~~
C:/mingw-w64/x86_64-8.1.0-posix-seh-rt_v6-rev0/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/bits/fs_path.h:163:5: note: candidate expects 0 arguments, 1 provided
The terminal process terminated with exit code: 1
Terminal will be reused by tasks, press any key to close it.
So, what you are seeing is an error message, not an output.
If the file bits/stdc++.h is not a file that you created,
then what you need to do is to replace
#include <bits/stdc++.h>
with
#include <iostream>
and that's gonna solve it for you.
I'm trying to compile the following code:
#include <boost/optional.hpp>
void foo(boost::optional<unsigned> x = boost::none);
placed in the file a.cu, with the CUDA compiler, using the following command line:
nvcc a.cu -c --std=c++11 -I/opt/boost/include
but I get a bunch of errors:
a.cu:2:53: error: conversion from ‘const boost::none_t(boost::none_t::init_tag (*)())’ to ‘boost::optional<unsigned int>’ is ambiguous
void foo(boost::optional<unsigned> x = boost::none);
^
/opt/boost/include/boost/optional/optional.hpp:805:1: note: candidate: boost::optional<T>::optional(boost::optional<T>::rval_reference_type) [with T = unsigned int; boost::optional<T>::rval_reference_type = unsigned int&&] <near match>
optional ( rval_reference_type val ) : base( boost::forward<T>(val) )
^ ~~~~
/opt/boost/include/boost/optional/optional.hpp:805:1: note: conversion of argument 1 would be ill-formed:
a.cu:2:53: error: invalid conversion from ‘const boost::none_t (*)(boost::none_t::init_tag (*)())’ to ‘unsigned int’ [-fpermissive]
void foo(boost::optional<unsigned> x = boost::none);
^
/opt/boost/include/boost/optional/optional.hpp:800:1: note: candidate: boost::optional<T>::optional(boost::optional<T>::argument_type) [with T = unsigned int; boost::optional<T>::argument_type = const unsigned int&] <near match>
optional ( argument_type val ) : base(val) {}
^ ~~~~
/opt/boost/include/boost/optional/optional.hpp:800:1: note: conversion of argument 1 would be ill-formed:
a.cu:2:53: error: invalid conversion from ‘const boost::none_t (*)(boost::none_t::init_tag (*)())’ to ‘unsigned int’ [-fpermissive]
void foo(boost::optional<unsigned> x = boost::none);
Why does this happen, and can I circumvent the problem while still actually using boost::optional in (host-side) code compiled with nvcc?
Additional information:
The code compiles fine with g++ 6.3.0 (my distribution's compiler).
This code (or rather, similar code) used to compile and work on an earlier Linux distribution I was using, where the compiler was g++ 5.4.x .
I've tried this with Boost versions 1.65.1 and 1.69.0 .
I've tried this with CUDA versions 9.2.88 and 10.0.130 .
I had the exact same error and was able to get this to work with this modification:
#define BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
#include <boost/optional.hpp>
This is using CUDA 10.0.130, g++ 7.3.0, and Boost 1.68.0.
A partial answer to the second question:
You could consider using Andrzej Krzemieński's neat and self-contained implementation of an optional instead of boost::optional. It works with C++11, which is what you seem to be doing.
I am trying to start a thread t:
#include <iostream>
#include <fstream>
#include <string>
#include <thread>
void function(int p1, int p2, int p3){
std::cout<<p1<<p2<<p3<<std::endl;
}
int main(int argc, char const *argv[]) {
std::cout<<"starting"<<std::endl;
std::thread t(function, 1, 2, 3);
std::cout<<"created thread"<<std::endl;
t.join();
std::cout<<"end"<<std::endl;
return 0;
}
My compiler tells me this:
doesntwork.cpp:12:15: error: no matching constructor for
initialization of 'std::thread'
std::thread t(function, 1, 2, 3);
^ ~~~~~~~~~~~~~~~~~
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:408:9: note:
candidate constructor template not viable: requires single
argument '__f', but 4 arguments were provided
thread::thread(_Fp __f)
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:289:5: note:
candidate constructor not viable: requires 1 argument, but 4
were provided
thread(const thread&);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:296:5: note:
candidate constructor not viable: requires 0 arguments, but
4 were provided
thread() _NOEXCEPT : __t_(_LIBCPP_NULL_THREAD) {}
^
1 error generated.
In the first case it tells me that for the thread t, there is no constructor that can use more than 1 parameter, while if I just remove the arguments (p1, p2, p3) it doesn't work either because I am not passing any argmuent....
Compiler information:
Configured with: --prefix=/Library/Developer/CommandLineTools/usr
--with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.2)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
built command used: g++ doesntwork.cpp -o doesntwork.out
Is there something different you have to do when compiling with threads? Am I missing something very obvious?
On macOS, g++ (from Xcode: Version 10.0 (10A255)) is aliased to clang which by default does not work with c++11 threads. To solve the problem you have to use the -std=c++11 switch.
Example:
g++ -std=c++11 fileToCompile.cpp -o outputFile.out
This should let you compile c++ code using c++11 threads.
Thank you to #M.M for providing the answer above in the comments.
I'm trying to run some code using threads in standard C++ (installed with XCode) in MacOS X Mavericks. But I'm getting some errors. Here's a minimal working example:
#include <thread>
#include <iostream>
void run (int x) {
std::cout<<".";
}
int main (int argc, char const *argv[])
{
std::thread t(run);
}
The error I'm getting:
minimal.cpp:10:17: error: no matching constructor for initialization of 'std::thread'
std::thread t(run,0);
^ ~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/thread:372:9: note: candidate constructor template not viable: requires single argument '__f', but 2 arguments
were provided
thread::thread(_Fp __f)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/thread:261:5: note: candidate constructor not viable: requires 1 argument, but 2 were provided
thread(const thread&);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/thread:268:5: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
thread() _NOEXCEPT : __t_(0) {}
^
1 error generated.
I've been able to track the problem to my compiler defining _LIBCPP_HAS_NO_VARIADICS, which is defined because of
#if !(__has_feature(cxx_variadic_templates))
#define _LIBCPP_HAS_NO_VARIADICS
#endif
Any help would be appreciated.
Thank you!
Thanks to pwny and PeterT, I figured out the error.
I just needed to compile with clang++ -std=c++11 minimal.cpp and it worked like a charm.
I also needed a t.join() at the end to prevent an execution error to happen.
i'm getting different std::thread behaviour running same app. on xcode or instruments (profiling), on xcode the single thread/multithread ratio is 0.6 and in instruments is 3.7 using a 4 thread array,
how is this possible?
Xcode run:
st...ok - lap: 4875 ms
st/8...ok - lap: 1205 ms
mt...ok - lap: 8330 ms
st/mt ratio:**0.6**
Instruments run:
st...ok - lap: 2182 ms
st/8...ok - lap: 545 ms
mt...ok - lap: 596 ms
st/mt ratio:**3.7**