C++: string = NULL gives SEGFAULT 11? -

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i modified project today allow save files in different folders, , found program crashed when startup:

segmentation fault: 11

because introduced many changes before testing program, started comment out functions added, no help. put

cout << "hello world" << endl; return 0;

as first 2 lines in int main(), still crashed without showing anything.

finally, took me 1 hour figure out error. modification includes declaring global variable

string foldername = null;

the line above seems innocence, declaring global variable.

then tried simple program:

#include <string>  std::string = null;  int main(){     return 0; }

and crashed @ startup.

why declaring string global variable null make program silently crashed without info?

the std::string - opposite inherited c char* strings - holds valid string. may empty, cannot null. if try initialise std::string null try blindly copy c-like string null address, undefined behaviour.

just use

std::string a;

and a initialised empty string.


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