I got following error message when building 2.4.0-rc1 with Visual Studio 2015 update 3. Attached "rc1_output.txt" is full-length nmake output.
2.4.0-preview3 doesn't have this error.
diff --git a/win32/mkexports.rb b/win32/mkexports.rb
index d26acbb107..8fc7d9ddb5 100755
--- a/win32/mkexports.rb
+++ b/win32/mkexports.rb
@@ -114,7 +114,7 @@ def each_export(objs)
when /OBJECT/, /LIBRARY/
next if /^[[:xdigit:]]+ 0+ UNDEF / =~ l
next unless /External/ =~ l
- next if /(?:_local_stdio_printf_options|v(f|sn?)printf_l)\Z/ =~ l
+ next if /(?:_local_stdio_printf_options|v(f|sn?)printf(?:_s)?_l)\Z/ =~ l
next unless l.sub!(/.*?\s(\(\)\s+)?External\s+\|\s+/, '')
is_data = !$1
if noprefix or /^[@_]/ =~ l