Assign a nullptr to a std::string is safe?

c++ string c++-standard-library
bardes picture bardes · May 27, 2012 · Viewed 19.6k times · Source

I was working on a little project and came to a situation where the following happened:

std::string myString;
#GetValue() returns a char*
myString = myObject.GetValue();

My question is if GetValue() returns NULL myString becomes an empty string? Is it undefined? or it will segfault?

Answer

thb picture thb · May 27, 2012

Interesting little question. According to the C++11 standard, sect. 21.4.2.9,

basic_string(const charT* s, const Allocator& a = Allocator());

Requires: s shall not be a null pointer.

Since the standard does not ask the library to throw an exception when this particular requirement is not met, it would appear that passing a null pointer provoked undefined behavior.

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