Win32 support: wcsnrtombs and mbsnrtowcs don't handle null output buffers correctly.

[andrew.j.c.parker]

Summary

According to the linux man pages:

http://man7.org/linux/man-pages/man3/wcsnrtombs.3.html
http://man7.org/linux/man-pages/man3/mbsnrtowcs.3.html

"If dest is NULL, len is ignored, and the conversion proceeds as above..."

The current code still uses len when the output buffer is NULL, i.e. the len *isn't* ignored.

The fix simply forces len to be the maz val for size_t when the output buffer is NULL.

[mclow.lists]

I believe that this accomplishes what Andrew is trying to do.
With the changes that I noted, this LGTM.

src/support/win32/support.cpp

79

You write (size_t)-1; here, but below in this same routine is the code:

return static_cast<size_t>(-1);

Please use one or the other.

[andrew.j.c.parker]

Updated patch based on comment about casting.

[Eugene.Zelenko]

Looks like patch was not committed.

[andrew.j.c.parker]

In D11348#554454, @Eugene.Zelenko wrote:

Looks like patch was not committed.

Sorry, my eyes aren't really on this project at the moment so haven't been keeping up.

Anything I can do to help? Do I need to do anything extra?

[mclow.lists]

If you don't have commit privs; I will commit it for you. (but it will be Thursday when I do so)

[mclow.lists]

(Finally) committed as revision 351971

src/support/win32/support.cpp

     size_t result = 0;
     bool have_result = false;
 
+    // If dst is null then max_dest_chars should be ignored according to the
+    // standard.  Setting max_dest_chars to a large value has this effect.
+    if (!dst)
+        max_dest_chars = static_cast<size_t>(-1);
+
     while ( source_remaining ) {
         if ( dst && dest_converted >= max_dest_chars )
             break;

     bool have_result = false;
     bool terminator_found = false;
 
+    // If dst is null then dst_size_bytes should be ignored according to the
+    // standard.  Setting dest_remaining to a large value has this effect.
+    if (!dst)
+        dest_remaining = static_cast<size_t>(-1);
+
     while ( source_converted != max_source_chars ) {
         if ( ! dest_remaining )
             break;