I am using wxWidgets 2.9.4 in Visual Studio 2012 and I keep getting these two error messages:
Error 1 error C2664: 'MessageBoxW' : cannot convert parameter 2 from 'const char *' to 'LPCWSTR'
IntelliSense: argument of type "const char *" is incompatible with parameter of type "LPCWSTR"
My code is:
#ifdef _WIN32
std::string msg;
StringFromFormatV(&msg, format, args);
retval = IDYES == MessageBox(0, msg.c_str(), "ERROR! Continue?", MB_ICONQUESTION | MB_YESNO);
You are compiling your project using multi-byte characters as default. You can change that in your project's properties, or you can use msg.wc_str(), or even enforce the use of MessageBoxA instead of using the macro MessageBox.
Related
I'm trying to open a file using a string parameter, however I'm getting the following error:
error C2664: 'void std::basic_ifstream<_Elem,_Traits>::open(const wchar_t *,std::ios_base::openmode,int)' : cannot convert parameter 1 from 'System::String ^' to 'const wchar_t *'
How do you convert System::String ^ to const wchar_t *?
As Hans points out, simple conversion is necessary. It would look similar to the following:
System::String ^str = L"Blah Blah";
pin_ptr<const wchar_t> convertedValue = PtrToStringChars(str); // <-- #include <vcclr.h>
const wchar_t *constValue = convertedValue; // <-- Unnecessary, but to be completely verbose
void std::basic_ifstream<_Elem, _Traits>::open(constValue, mode, i);
I am making program in which i try to make boost packaged_task then take its future in vector and launch it with asio post.
when i try to make packaged_task ,it gives me this error:
Error C2440 'return': cannot convert from 'void (__cdecl &)(boost::asio::yield_context)' to 'void (&)(boost::asio::yield_context)'
this is the relevant code:
typedef boost::packaged_task<std::string(boost::asio::yield_context)> task_t;
boost::shared_ptr<task_t> task = boost::make_shared<task_t>(boost::bind(&HTTPRequest::Execute, mClientRequestsVariables[m_HttpClient_request_name]->shared_from_this() , boost::placeholders::_1, m_HttpClient_request_name, Get_mHTTPClient_Responses_Map_shared_pointer()));
boost::future<std::string> fut = (task->get_future());
mPendingData.push_back(std::move(fut)); // C++11 possible: (std::move(fut) when fut is a unique_future);
mIos.post(boost::bind(&task_t::operator(), task));
and this is the definition of HTTPRequst::Execute :
HTTPRequest::HTTPRequest(boost::asio::io_service& ios, unsigned int id, std::string URL, const HTTPServiceResolve& resolve_addr, boost::shared_ptr<LoggingClass_2> mHTTPRequest_LoggingInstance_shared_pointer)
and the class HTTPRequest is derived from enable_shared_from_this .
the error is in bind.hpp so i find in vs output windows clues to the included part of code.
why is this error happening?and what is the solution??
hi I learn module these day. Today I write a simple module that would take string parameter when using insmod here is code snippet:
....
static char *city = "NULL";
MODULE_PARM(city, charp,0000);
....
when I type in command line
insmod modulename.ko city="newyork"
it's ok
but when I type
insmod modulename.ko city="new york"
there is error
insmod: error inserting 'modulename.ko': -1 Unknown symbol in module
do you know why?
Basically, my problem is a signed char to int and string conversion in cocoa.
I found this piece of code in an open source cocoa bluetooth application and am trying to apply it to my own.
Basically, I get a signed char output from the variable "RSSI", and want to convert it to an int and a string, the string for outputting to the log and the int for further calculation. However, no matter what I try, I cannot seem to get it converted, and just get an EXEC_BAD_ACCESS if I try outputting the signed char to the log as it is.
A typical value for the signed char would be " -57 '\307' " quoted directly from the process before it is held up by the NSLog. Here's the code:
- (BOOL)isInRange {
BluetoothHCIRSSIValue RSSI = 127; /* Valid Range: -127 to +20 */
if (device) {
if (![device isConnected]) {
[device openConnection];
}
if ([device isConnected]) {
RSSI = [device rawRSSI];
[device closeConnection];
NSLog(RSSI);
}
}
return (RSSI >= -60 && RSSI <= 20);
}
Thanks in advance.
NSLog() takes an NSString format string as its first argument, and an (optional) variable length list of variables for the format specifiers in the format string after that:
NSLog(#"RSSI: %c", RSSI);
What you've got now (NSLog(RSSI);) is simply wrong. It should be giving you compiler warnings like these:
warning: passing argument 1 of 'NSLog' makes pointer from integer without a cast
warning: format not a string literal and no format arguments
You should always pay attention to compiler warnings, not ignore them. Especially when your program crashes on the same line the warnings refer to, they should be a red flag to you that you've made a mistake.
As an aside, I should mention that NSLog() works very much like printf(). The two major differences are that NSLog's format string should be an Objective-C string literal (#"string"), not a standard C char string ("string"), and that the format specifier for an object is %#. %# is replaced by the string returned by calling the -description method on the object to be printed.
I am compiling QCAR SDK, but it prompts an error after I added more frameworks to the project.
// Matrices.h
//
#ifndef _QCAR_MATRIX_H_
#define _QCAR_MATRIX_H_
namespace QCAR
{
/// Matrix with 3 rows and 4 columns of float items
struct Matrix34F {
float data[3*4]; ///< Array of matrix items
};
/// Matrix with 4 rows and 4 columns of float items
struct Matrix44F {
float data[4*4]; ///< Array of matrix items
};
} // namespace QCAR
#endif //_QCAR_MATRIX_H_
In the line namespace QCAR, it said Unknown type name 'namespace'.
What should I do?
UPDATE: Here is the build transcript
In file included from ../../build/include/QCAR/Tool.h:18:
In file included from /Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/EAGLView.h:14:
In file included from /Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/ImageTargetsAppDelegate.h:9:
In file included from /Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/CouponBook.m:12:
../../build/include/QCAR/Matrices.h:16:1: error: unknown type name 'namespace' [1]
namespace QCAR
^
../../build/include/QCAR/Matrices.h:16:15: error: expected ';' after top level declarator [1]
namespace QCAR
^
;
fix-it:"../../build/include/QCAR/Matrices.h":{16:15-16:15}:";"
In file included from /Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/ImageTargetsAppDelegate.h:9:
In file included from /Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/CouponBook.m:12:
/Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/EAGLView.h:52:5: error: type name requires a specifier or qualifier [1]
QCAR::Matrix44F projectionMatrix;
^
/Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/EAGLView.h:52:10: error: expected expression [1]
QCAR::Matrix44F projectionMatrix;
^
/Users/Raptor.Kwok/Documents/xCodeProjects/qcar-ios-1-0-0/samples/ImageTargets/ImageTargets/EAGLView.h:52:5:{52:5-52:9}: warning: type specifier missing, defaults to 'int' [-Wimplicit-int,3]
QCAR::Matrix44F projectionMatrix;
^~~~
1 warning and 4 errors generated.
You can rename your file with .mm or you can select your .m file and change the "File Type" to "Objective-C++ Source".
I suspect the translation is C or Objective-C, where namespace is not a keyword as it is in C++ and Objective-C++.
Another possibility is that a previous header did not close a body (e.g. forgotten }; at end of class declaration of forgotten } at end of function definition).