Fixes #59

doc/container.qbk

@@ -1221,6 +1221,7 @@ use [*Boost.Container]? There are several reasons for that:
 * Fixed bugs:
    * [@https://github.com/boostorg/container/pull/54 GitHub #54: ['"no sbrk() in VxWorks, configure dlmalloc to use only mmap"]].
    * [@https://github.com/boostorg/container/issues/58 GitHub #58: ['"Comparing strings does not compile in gcc 7+ in C++17 mode"]].
+   * [@https://github.com/boostorg/container/issues/59 GitHub #59: ['"basic_string::npos is missing its definition"]].
 
 [endsect]
 

include/boost/container/string.hpp

@@ -2955,6 +2955,10 @@ wstring;
 
 #else
 
+template <class CharT, class Traits, class Allocator>
+const typename basic_string<CharT,Traits,Allocator>::size_type
+   basic_string<CharT,Traits,Allocator>::npos;
+
 template<class S>
 struct is_string
 {