explaining what exceptions::what is and my errors.

[numLOCK]

hi there guys. i'm having problems understanding this error!

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

Does this mean i have to throw an exception like this tutorial?
http://www.cplusplus.com/reference/exception/exception/what/

should i post my code here because my professor told me i can't post anything on this forum and he checks!

[Zhuge]

You should inspect the call stack and see where in your code you are performing the operation that ends up leading to the exception. That specific error, as I recall, is likely from passing a char* that is null to an std::string. Please confirm you aren't doing that.

[JLBorges]

#include <string>
#include <iostream>

int main()
{
    std::string stra ; // fine, default constructed
    std::cout << "1\n" << std::flush ;
    
    std::string strb = "hello" ; // fine, constructed with const char*
    std::cout << "2\n" << std::flush ;

    std::string str(nullptr) ; // *** error: null pointer 
    std::cout << "3\n" << std::flush ;
}

g++ -std=c++11 -O2 -Wall -Wextra -pedantic-errors -g -O0 main.cpp && ./a.out
1
2
terminate called after throwing an instance of 'std::logic_error'
  what():  basic_string::_S_construct null not valid
bash: line 7:  9199 Aborted                 (core dumped) ./a.out

http://coliru.stacked-crooked.com/a/40721b599d510f35


> my professor told me i can't post anything on this forum and he checks!

You professor is being asinine, and I hope he reads this when he checks.