CODEWITHSUNDEEP
c++string
Isini Dananjana
Isini Dananjana

Reputation: 1

How to append char pointer to std::string in C++

  char * val = ep->GetValue();
  std::string m="zValue:" + (std::string)val;

ep->GetValue() returns a char pointer. I want to append it to a string. I tried as above but it throws the following error.

terminate called after throwing an instance of 'std::logic_error'
what():  basic_string::_M_construct null not valid

Upvotes: 0

Views: 1297

Answers (2)

Pepijn Kramer
Pepijn Kramer

Reputation: 12956

Or in reusable form :

#include <string>
#include <iostream>

std::string string_from_ptr(const char* p)
{
    std::string retval;
    if (p != nullptr) retval = p;
    return retval;
}


int main()
{
    char* p{ nullptr };
    std::cout << string_from_ptr(p);
    // auto str = string_from_ptr(ep->GetValue());
}

Upvotes: 0

m88
m88

Reputation: 1988

You get this error because you try to build a std::string from a nullptr. Try:

std::string m = "zValue:";
if(char * val = ep->GetValue()) m += val;

Upvotes: 4

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