I am trying to create a thread which is running the IO service of boost's asio.
However, I got the following compilation error. Is there any way to solve it?
Environment: gcc 4.7.2, boost 1.54
error: left operand of comma operator cannot resolve address of overloaded function
error: invalid static_cast from type ‘boost::asio::io_service’ to type ‘size_t (boost::asio::io_service::*)() {aka long unsigned int (boost::asio::io_service::*)()}’
Code:
boost::asio::io_service oSer;
std::thread t(std::bind(static_cast<size_t (boost::asio::io_service::*)()>(&boost::asio::io_service::run, oSer)));
t.join();
How about using lambda expression?
std::thread t([&oSer](){ oSer.run(); });
If you don't like to use lambda, try this
std::thread t(std::bind(static_cast<size_t(boost::asio::io_service::*)()>(&boost::asio::io_service::run), &oSer));
Related
I'm trying to write some JNA code that accesses glibc, specifically functions defined in mmap.h.
I have tried to define it exactly as shown in man shm_open. The getuid() function call just before it works, but shm_open doesn't return.
I'm constrained to using JNA 4.4.0 and JNA Platform 3.4.0.
interface LibC extends Library {
LibC INSTANCE = Native.loadLibrary("c", LibC.class);
int shm_open(String name, int oFlag, int mode);
}
// ...
int fileDescriptor = LibC.INSTANCE.shm_open("/some_memory.123", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
// ...
I expect a file descriptor to be returned, but I get these exceptions:
When I load "libc.so.6": java.lang.UnsatisfiedLinkError: Error looking up function 'shm_open': /lib/x86_64-linux-gnu/libc.so.6: undefined symbol: shm_open
When I load "c": java.lang.UnsatisfiedLinkError: Error looking up function 'shm_open': /usr/lib/jvm/java-8-openjdk-amd64/bin/java: undefined symbol: shm_open
Well, I figured out the issue while writing the question.
While getuid() and friends are defined in libc, shm_open and friends are defined in librt. I really should have realized that because the manpage for shm_open explicitly states "Link with -lrt", indicating it residing in the "rt" lib.
In short: I need a new interface for LibRT alongside LibC, loaded with name rt.
I was working on a project and got the following errors
Error (active) the default constructor of "Input" cannot be referenced -- it is a deleted function EquationSolver c:\Users\Kim\Documents\Visual Studio 2015\Projects\EquationSolver\EquationSolver\main.cpp 10
Error C2280 'Input::Input(void)': attempting to reference a deleted function EquationSolver <project_dir>\main.cpp 10
Since it is almost impossible to find the cause of the error from this, I tried compiling with gcc with -Wall and got following output
main.cpp: In function 'int main()':
main.cpp:10:9: error: use of deleted function 'Input::Input()'
Input input;
^~~~~
In file included from main.cpp:2:0:
Input.hpp:16:7: note: 'Input::Input()' is implicitly deleted because the default definition would be ill-formed:
class Input
^~~~~
Input.hpp:16:7: error: use of deleted function 'Expressions::Expressions()'
In file included from Input.hpp:11:0,
from main.cpp:2:
Expressions.hpp:8:7: note: 'Expressions::Expressions()' is implicitly deleted because the default definition would be ill-formed:
class Expressions
^~~~~~~~~~~
Expressions.hpp:8:7: error: uninitialized reference member in 'class Expressions'
Expressions.hpp:17:8: note: 'Expressions::Vec& Expressions::left' should be initialized
Vec& left;
^~~~
Expressions.hpp:8:7: error: uninitialized reference member in 'class Expressions'
class Expressions
^~~~~~~~~~~
Expressions.hpp:18:8: note: 'Expressions::Vec& Expressions::right' should be initialized
Vec& right;
^~~~~
This output is much more verbose and quickly helped me find the origin, which was a misplaced & (class member should be Vec left, was Vec& left).
Is it possible to make Visual Studio as verbose?
When putting Visual Studio to /Wall, I get >1800 warnings, most completely unrelated to my project, but I still only get those two errors.
I am using an extensive piece of code which compiles in Windows and Linux with gcc>=4.7. It is a utility to seamlessly generate mex functions in Matlab from m-scripts written by someone. I am having trouble compiling a short c script (not provided here) in Mac os x. I am using gcc-4.8 with C++11. It uses Boost library only for headers. The piece of utility code where it gets stuck is:
/* gets mxClassID, given C type>
eg. mx_class_id<float>()*/
template<typename T>
struct mx_class_id
{
operator mxClassID()
{
return static_cast<mxClassID>(boost::mpl::at<mxInverseTypeMap,T>::type::value);
}
};
required by
template<typename T>
mxArray* mxCreateScalar(const T & val)
{
//mxClassID cid=static_cast<mxClassID>(boost::mpl::at<mxInverseTypeMap,T>::type::value);
mxArray * arr=mxCreateNumericMatrix(1,1,mx_class_id<T>(),mxREAL);
mxSetValue(arr,val);
return arr;
}
What am I missing? Is it conflicting with built-in clang libraries? Or is it a header not specified (boost/mpl/at.hpp is included)? As I mention it does compile in Matlab for Windows and Linux.I have tried boost 1.51.0 (this is what we use) and also 1.56.0 (this is what Matlab uses) but I get the same error message.
The code I use to compile is
mex -v /usr/local/bin/gcc-4.8 -I path-to-boost-library -I path-to-private-library -I /usr/local/lib -std=C++11 script.cc
Here is the error message I am getting:
error: 'value' is not a member of 'boost::mpl::aux::wrapped_type <
boost::mpl::aux::type_wrapper < mpl_::void_> > ::type {aka
mpl_::void_}'
Any pointers or help appreciated. Thanks
This was resolved by the conflicting use of 'size_t' and 'unsigned long int'.
I think in Linux, Windows, size_t was employed in the code with the assumption it to be uint64_t. And it compiled in both.
However, for mac os x, it is either size_type or unsigned long int. This especially created problem because the code was matching c type to Matlab mex type with one-to-one mapping. In inverse mapping, with the use of size_t this one-to-one mapping was getting lost and instead became many-to-one. Once that was addressed it was easy to fix the rest.
I have written a callback method and when I am trying to compile the project in vs2012, I am getting the following error:
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C2143: syntax error : missing ',' before '&'
the both error present in same line.
These are the following code which I am trying:
#include <windows.h>
#include "atlstr.h"
///////////////////////////////////////////////////////////////////////////////
class CInf;
typedef BOOL (*PENUMDEVCALLBACK)(CInf* inf, const CString& devname, const CString& instsecname, const CStringArray& devid, PVOID context, DWORD& code);
I think the error will be present in CStringArray& argument because when I include the afxcoll.h.
the fatal error C1189: #error : WINDOWS.H already included. MFC apps must not #include <windows.h>.
When I removed the windows.h. the above error gone but I need windows.h header also.
Any idea how to include windows.h and afxcoll.h in same file.
It is not possible to include only isolated parts of the MFC. When you want to use CStringArray you Need to include the afx.h or afxwin.h file.
It is possible to use CString alone. If you just want an Array of CString and you don't Need the complete MFC than it is easier to use std::vector. CString works perfect with all STL container.
I've been trying to implement PIMPL using the g++ compiler on my local CygWin install and I'm beginning to think it may be the fact that I'm running g++ 4.3.4, inasmuch as its C++11 support is less than perfect.
With the very baseline code (from MSDN here):
my_class.h:
#include <memory>
class my_class {
public:
my_class();
private:
class impl; unique_ptr<impl> pimpl(new impl);
};
my_class.cpp:
#include "my_class.h"
class my_class::impl { int my_int; };
my_class::my_class(): pimpl( new impl ) {};
I try to compile with g++ -std=c++0x -o my_class.o my_class.cpp and end up with:
In file included from my_class.cpp:1:
my_class.h:8: error: ISO C++ forbids declaration of 'unique_ptr' with no type
my_class.h:8: error: invalid use of '::'
my_class.h:8: error: expected ';' before '<' token
my_class.cpp: In constructor 'my_class::my_class()':
my_class.cpp:5: error: class 'my_class' does not have any field named 'pimpl'
I also get that if I substitute -std=gnu++0x.
In fact, when I try to compile even the simplest file, lifted from another SO answer:
#include <iostream>
#include <memory>
int main() {
std::unique_ptr<int> up( new int( 30 ) );
}
it complains that unique_ptr is not in the std namespace.
The gcc c++11 support page has no entry for unique_ptr but, from looking at the net, it's been around for quite a while, at least since 4.4.
So my question is, firstly, at what version of gcc was support for unique_ptr added?
And, secondly, am I just making some bonehead mistake in my code, using it the wrong way?
In your first example, the std:: qualifier is missing on unique_ptr. The second example is correct C++11.
According to the GCC 4.4 release notes, unique_ptr was not in GCC's standard C++ library before 4.4:
Improved experimental support for the upcoming ISO C++ standard, C++0x, including:
...
unique_ptr, <algorithm> additions, exception propagation, and support for the new character types in <string> and <limits>.