Usage of macros in std::string source

Question

I'm writing some c++ code that makes use of std::string.
I wanted to see how to code is written, so I went into the source code. (ctrl + left click).
I noticed, that there are macros everywhere.
The code even ends with:

_STD_END
// Corresponds to: #define _STD_END }

I get why macros are useful, and I use them for my own Log.hpp file, but I don't understand why anyone would use macros such as _STD_END instead of just writing }.

Just to clear up, my question is why he author of std::string, P.J. Plauger, decided to use macros in this way, and if I also should?

Answer 1

That’s the Dinkumware library, which Microsoft licenses (although they've recently taken over full maintenance of their version). The _STD_BEGIN and _STD_END macros are used for customizing the std namespace. Some compilers don't (didn't?) support namespaces; for those compilers, the macro expansions are empty. Some compilers need some indirection, and those macros expand into directives that put the code into an implementor-specific namespace (i.e., a namespace whose name begins with an underscore followed by a capital letter), which may or may not be complemented by a using-directive to pull the contents of that namespace into std. And in many cases they expand into the obvious, ordinary namespace std { and }, respectively.

In short, they're about configurability for a multi-platform library implementation.

I worked for Dinkumware for quite a few years, so I have first-hand knowledge.