CODEWITHSUNDEEP
c++stringdata-conversion
barej
barej

Reputation: 1406

C++ convert int to string inline

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 ...!");

Upvotes: 3

Views: 2701

Answers (3)

Jonathan Mee
Jonathan Mee

Reputation: 38969

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__)

Upvotes: 3

Max Lybbert
Max Lybbert

Reputation: 20047

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.

Upvotes: 1

Maxim Akristiniy
Maxim Akristiniy

Reputation: 2126

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__))

Upvotes: 1

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