Will std::string.assign(const char) or op= ( with const char ) create a copy of the char*?

Question

Digging through the c++ code, it looks like it does a copy, but I cannot be sure. By "copy", I mean something like strcpy is happening internally. And std:string doesn't end up with a pointer to the same char* internally it was passed.

const char *somestring = ...
std::string str;
str.assign(somestring);
// or
str = somestring;  //in my impl, op= calls to assign(const char*)

score 2 · Accepted Answer · edited May 23 '17 at 12:21

2

std::string will always copy from the array pointed to by a char *. You can also provide an iterator range in some constructors.

Copy or reference counting during copies of one std::string to another depends on the C++ library that you are using.

The C++ 2011 standard requires std::string to make real copies. The 2003 standard allowed reference counted copies.

The GNU libstdc++ uses reference counted strings. And for backward compatibility, even the 2011 standard GCC builds with them. Otherwise it couldn't link to code built with the 2003 standard.

There is a preprocessor definition to turn on the new behavior.

See also std::string copy constructor NOT deep in GCC 4.1.2? and Is std::string refcounted in GCC 4.x / C++11?

edited May 23 '17 at 12:21

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answered Sep 05 '14 at 18:50

Zan Lynx

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Reference counting can happen when copying strings. But this question is about copying a `const char *`, which cannot be reference counted. – interjay Sep 05 '14 at 18:52
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@interjay: Also mentions operator= though. – Zan Lynx Sep 05 '14 at 18:52
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It mentions `operator=` with a `const char*` parameter. – interjay Sep 05 '14 at 18:54
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@interjay: I can see how you read it that way, although I didn't. – Zan Lynx Sep 05 '14 at 18:55
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@interjay yes, operator= w/ const char* is what I meant. Sorry for confusion. – marathon Sep 05 '14 at 18:55
good to know about string to string copy behavior, too. Thanks. – marathon Sep 05 '14 at 19:29

Will std::string.assign(const char) or op= ( with const char ) create a copy of the char*?

1 Answers1

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Will std::string.assign(const char*) or op= ( with const char *) create a copy of the char*?

1 Answers1

Linked

Will std::string.assign(const char) or op= ( with const char ) create a copy of the char*?