MSVC_NMake/README: Add note on mixing between MSVC 2015~2019

Let people know that it is recommended to use the same Visual Studio
version, even when using 2015, 2017 or 2019, to build software that
depends on cairomm.

Also note a new NMake option that allows creating MSVC 2015-style DLL
and .lib filenames if that is needed, but note that is generally not
recommended.

1 files changed, 6 insertions, 0 deletions

diff --git a/MSVC_NMake/README b/MSVC_NMake/README
index 7ff0da1..3064f92 100644
--- a/MSVC_NMake/README
+++ b/MSVC_NMake/README
@@ -5,6 +5,12 @@ Building cairomm with Visual Studio .NET 2015 or later
 * Install the latest Win32 GTK+ Development files from ftp://ftp.gnome.org/pub/GNOME/binaries/win32/gtk+/ and add

   the paths to headers and import libraries to Visual Studio, if they are not already in

   $(srcroot)/../vs$(VSVER)/$(Platform).

+* It is recommended (and possibly required) that you build cairomm and software that depends on cairomm with the

+  same compiler, even though Microsoft tried hard to make things API and ABI compatible between Visual Studio

+  2015, 2017 and 2019, so the build distinguishes between these versions with 'vc140' (2015), 'vc141' (2017) and

+  'vc142' (2019) in the output DLL and .lib filenames, as per the toolset version as Microsoft defined.  If using

+  'vc140' in the DLL and .lib names are desired (such as when rebuilding software that depends on cairomm is

+  not convenient), pass in 'USE_COMPAT_LIBS=1' in your NMake command line (note that doing this is not recommended).

 * In a Visual Studio command prompt, go to $(srcroot)\MSVC_NMake

 * Build using nmake /f Makefile.vc CFG=[release|debug].

 * Run the tests