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Re: Putting two colons before std -- is it ever needed?

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On 2019-09-25 at 10:02, Frederick Gotham wrote:
> 
> Occasionally I see people write code like this:
> 
> #include <string>
> 
> int main()
> {
>      ::std::string str;
> }
> 
> I think you would only ever need to put those two colons before 'std' if you created a class or a namespace called 'std', and of course if you did, then it would have to be inside another namespace (because otherwise you'd have a name clash).
> 
> I tried compiling the following code, and each time it created a 'string' from the C++ standard library.
> 
> So the question I ask is if there is **ever** any situation when it's necessary to put two colons before 'std'?
> 
> #include <string>
> #include <iostream>
> 
> namespace Monkey {
> 
> 	class nonstd {
> 		int i;
> 	};
> 	
> 	class mutant : public nonstd {
> 		int j;
> 	};
> 	
> 	class mongrel : public nonstd {
> 		int k;
> 	};
> 	
> 	class std {
> 	public:
> 		typedef char *string;
> 	};
> }
> 
> int SomeFunc()
> {
> 	using namespace Monkey;
> 	
> 	std::string a;
> 	
> 	::std::string b;
> 	
> 	::std::cout << sizeof(a) << " " << sizeof(b) << ::std::endl;
> }
> 
> int main()
> {
> 	std::string a;
> 	
> 	::std::string b;
> 	
> 	::std::cout << sizeof(a) << " " << sizeof(b) << ::std::endl;
> 	
> 	SomeFunc();
> }
> 

It would be a problem if SomeFunc() were also a member of the Monkey 
namespace, and one of your coworkers added his own std::string to it.

It that case it is probably time better spent to have a serious talk 
with your collegue, rather than to fill up the code base with millions 
of :: during the next decades.


  Bo Persson

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Thread

Putting two colons before std -- is it ever needed? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-09-25 01:02 -0700
  Re: Putting two colons before std -- is it ever needed? Ian Collins <ian-news@hotmail.com> - 2019-09-25 20:15 +1200
  Re: Putting two colons before std -- is it ever needed? David Brown <david.brown@hesbynett.no> - 2019-09-25 12:22 +0200
    Re: Putting two colons before std -- is it ever needed? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-09-25 03:48 -0700
  Re: Putting two colons before std -- is it ever needed? Bo Persson <bo@bo-persson.se> - 2019-09-25 15:48 +0200
    Re: Putting two colons before std -- is it ever needed? Vir Campestris <vir.campestris@invalid.invalid> - 2019-09-26 21:51 +0100
  Re: Putting two colons before std -- is it ever needed? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-09-25 10:02 -0400
    Re: Putting two colons before std -- is it ever needed? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-09-25 10:11 -0400
    Re: Putting two colons before std -- is it ever needed? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-09-25 07:17 -0700
  Re: Putting two colons before std -- is it ever needed? Stuart Redmann <DerTopper@web.de> - 2019-09-25 19:51 +0200
    Re: Putting two colons before std -- is it ever needed? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-09-25 15:37 -0400
    Re: Putting two colons before std -- is it ever needed? Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-09-26 00:01 -0700
  Re: Putting two colons before std -- is it ever needed? woodbrian77@gmail.com - 2019-09-27 08:50 -0700
    Re: Putting two colons before std -- is it ever needed? scott@slp53.sl.home (Scott Lurndal) - 2019-09-27 16:25 +0000
      Re: Putting two colons before std -- is it ever needed? woodbrian77@gmail.com - 2019-09-27 11:40 -0700
        Re: Putting two colons before std -- is it ever needed? scott@slp53.sl.home (Scott Lurndal) - 2019-09-27 20:19 +0000

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