windows fixes.

doc/reference/bind_launcher.adoc

@@ -12,4 +12,5 @@ auto bind_launcher(Launcher && launcher, Init && ... init);
 // The new launcher with bound paramaters
 template<typename ... Init>
 auto bind_default_launcher(Init && ... init);
-----
+----
+

doc/stdio.adoc

@@ -42,9 +42,11 @@ include::../example/stdio.cpp[tag=null]
 == `native_handle`
 
 A native handle can be used as well, which means an `int` on posix or a `HANDLE` on windows. 
-Furthermore, any object that has a `native_handle` returning that native handle type is valid, too.
+Furthermore, any object that has a `native_handle` function which returns a valid type for a stdio stream.
 
-.example/stdio.cpp:51-56
+E.g. a domain socket on linux.
+
+.example/stdio.cpp:52-57
 [source,cpp]
 ----
 include::../example/stdio.cpp[tag=native_handle]
@@ -55,7 +57,7 @@ include::../example/stdio.cpp[tag=native_handle]
 Additionally, process v2 provides a `popen` class. 
 It starts a process and connects pipes for stdin and stdout, so that the popen object can be used as a stream.
 
-.example/stdio.cpp:61-64
+.example/stdio.cpp:63-66
 [source,cpp]
 ----
 include::../example/stdio.cpp[tag=popen]

example/stdio.cpp

@@ -46,6 +46,7 @@ int main(int argc, char *argv[])
     proc.wait();
     //end::null[]
   }
+#if defined(BOOST_POSIX_API)
   {
     //tag::native_handle[]
     asio::io_context ctx;
@@ -56,6 +57,7 @@ int main(int argc, char *argv[])
     proc.wait();
     //end::native_handle[]
   }
+#endif
   {
     //tag::popen[]
     asio::io_context ctx;

include/boost/process/v2/stdio.hpp

@@ -82,11 +82,11 @@ struct process_io_binding
   process_io_binding() = default;
 
   template<typename Stream>
-  process_io_binding(Stream && str, decltype(std::declval<Stream>().native_handle()) = {})
+  process_io_binding(Stream && str, decltype(std::declval<Stream>().native_handle())* = nullptr)
       : process_io_binding(str.native_handle())
   {}
 
-  process_io_binding(FILE * f) : process_io_binding(::_get_osfhandle(_fileno(f))) {}
+  process_io_binding(FILE * f) : process_io_binding(reinterpret_cast<HANDLE>(::_get_osfhandle(_fileno(f)))) {}
   process_io_binding(HANDLE h) : h{h, get_flags(h)} {}
   process_io_binding(std::nullptr_t) : process_io_binding(filesystem::path("NUL")) {}
   template<typename T, typename = typename std::enable_if<std::is_same<T, filesystem::path>::value>::type>
@@ -168,7 +168,7 @@ struct process_io_binding
   process_io_binding() = default;
 
   template<typename Stream>
-  process_io_binding(Stream && str, decltype(std::declval<Stream>().native_handle()) = {})
+  process_io_binding(Stream && str, decltype(std::declval<Stream>().native_handle()) * = nullptr)
           : process_io_binding(str.native_handle())
   {}