C++ convert int to string inline - c++

Question

My problem seems to be very basic but I could not find a solution for it. I need to write a code which helps debugging by reporting the line and location of exception throwing. The problem is that __LINE__ is an int value and I have problem with its conversion into string in the following code where std::string(line) is used:
#pragma once
#include <stdexcept>
#include <cstring>
class CRuntime_error_line: public std::runtime_error
{
public:
CRuntime_error_line(const char * msg, const char * file,int line)
:runtime_error(std::string(msg)+" #"+":"+std::string(line)){}
};
#define runtime_error_line(msg) CRuntime_error_line(msg,__FILE__,__LINE__)
Seems std::string(line) cannot convert int to string and other solutions suggested online cannot be implemented inline and I don't know how to call a base constructor in second line!
compiler output:
log.h: In constructor ‘CRuntime_error_line::CRuntime_error_line(const
char*, const char*, int)’: log.h:10:124: error: invalid conversion
from ‘int’ to ‘const char*’ [-fpermissive] CRuntime_error_line(const
char * msg, const char * file,int
line):runtime_error(std::string(msg)+" #"+":"+std::string(line)){}
(Using g++ and linux environment)
edit:
the macro is supposed to be called this way:
throw runtime_error_line("Invalid somethihng ...!");

Answer 1

As is suggested by Borgleader std::to_string is your solution. It will also construct a temporary std::string for you, so there's no need to construct a temporary string from msg:
#pragma once
#include <stdexcept>
#include <cstring>
#include <string> // Add this to support std::to_string
class CRuntime_error_line: public std::runtime_error
{
public:
CRuntime_error_line(const char* msg, const char* file, int line)
: runtime_error(msg + " #:"s + std::to_string(line)){} // Use std::to_string here
};
#define runtime_error_line(msg) CRuntime_error_line(msg, __FILE__, __LINE__)
Without C++11 you can still do this it's just not as clean:
#pragma once
#include <stdexcept>
#include <cstring>
#include <sstream> // Use to include std::ostringstream
class CRuntime_error_line: public std::runtime_error
{
public:
CRuntime_error_line(const char* msg, const char* file, int line)
: runtime_error(static_cast<std::ostringstream&>(std::ostringstream() << msg << " #:" << line).str()){} // Use std::ostringstream here
};
#define runtime_error_line(msg) CRuntime_error_line(msg, __FILE__, __LINE__)

Answer 2

int this case may be better :
#define STRING_DEFINE1(x) #x
#define STRING_DEFINE(x) STRING_DEFINE1(x)
...
CRuntime_error_line(msg,__FILE__,STRING_DEFINE(__LINE__))

Answer 3

The simplest thing I can think of would be to write a to_string yourself:
#include <sstream>
std::string to_string(int i)
{
std::ostringstream os;
os << i;
return os.str();
}
Then call it as others have suggested.