std:: not needed for sort on macbook compilers

So I just noticed today that I don't need to declare the namespace for the sort on my macbook.

The following code compilers on my mac, but not my on my linux workstation (which uses vanilla g++)

#include <iostream>
#include <ctime>
#include <vector>

int main()
{
  std::vector<int> vec{1,2,3};   //needs std:: to compile on both mac and linux
  sort(vec.begin(), vec.end());  //doesn't need std:: to compile on mac
}

This is the information for my g++ compiler that compiles the above code with no issues.

Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

Does XCode do something behind the scenes that makes the sort function available without declaring its namespace? What is it doing, and why does it allow for this?