[glibmm] Meson build: Fix versioning on macOS

[Kjell Ahlstedt <kjellahl src gnome org>]

commit a7befa0b936e43b765c9d0b2716a8a27e5c87a11
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed Sep 30 17:19:02 2020 +0200

    Meson build: Fix versioning on macOS
    
    See https://github.com/libsigcplusplus/libsigcplusplus/pull/65

 gio/giomm/meson.build   | 5 ++++-
 glib/glibmm/meson.build | 5 ++++-
 meson.build             | 7 ++++++-
 3 files changed, 14 insertions(+), 3 deletions(-)
---
diff --git a/gio/giomm/meson.build b/gio/giomm/meson.build
index 4ab1aa8c..133ed8c6 100644
--- a/gio/giomm/meson.build
+++ b/gio/giomm/meson.build
@@ -3,7 +3,8 @@
 # Input: giomm_build_dep, giomm_pcname, maintainer_mode, project_source_root,
 #        generate_binding_py, handle_built_files_py, m4_files, pm_files,
 #        glibmm_libversion, install_includedir, python3, giomm_rc, gmmproc_dir,
-#        is_host_windows, gmmproc, generate_wrap_init_pl, giomm_libname
+#        is_host_windows, gmmproc, generate_wrap_init_pl, giomm_libname,
+#        macos_darwin_versions
 # Output: giomm_hg_ccg_basenames, giomm_extra_h_files, built_files_root,
 #         giomm_built_h_file_targets, giomm_dep
 
@@ -308,6 +309,7 @@ if maintainer_mode
   giomm_library = library(giomm_libname, extra_giomm_objects,
     giomm_used_built_cc_file_targets, giomm_extra_cc_files, built_dummy_h_file_target,
     version: glibmm_libversion,
+    darwin_versions: macos_darwin_versions,
     include_directories: extra_include_dirs,
     cpp_args: giomm_cpp_flags,
     dependencies: giomm_build_dep,
@@ -356,6 +358,7 @@ else # not maintainer_mode
   giomm_library = library(giomm_libname, extra_giomm_objects,
     built_cc_files, giomm_extra_cc_files,
     version: glibmm_libversion,
+    darwin_versions: macos_darwin_versions,
     include_directories: extra_include_dirs,
     cpp_args: giomm_cpp_flags,
     dependencies: giomm_build_dep,
diff --git a/glib/glibmm/meson.build b/glib/glibmm/meson.build
index b24fea4d..ba3bb0ed 100644
--- a/glib/glibmm/meson.build
+++ b/glib/glibmm/meson.build
@@ -3,7 +3,8 @@
 # Input: glibmm_build_dep, glibmm_pcname, maintainer_mode, project_source_root,
 #        generate_binding_py, handle_built_files_py, m4_files, pm_files,
 #        glibmm_libversion, install_includedir, python3, glibmm_rc, gmmproc_dir,
-#        is_host_windows, gmmproc, generate_wrap_init_pl, glibmm_libname
+#        is_host_windows, gmmproc, generate_wrap_init_pl, glibmm_libname,
+#        macos_darwin_versions
 # Output: glibmm_hg_ccg_basenames, glibmm_extra_h_files, built_files_root,
 #         glibmm_built_h_file_targets, glibmm_h_m4_files, glibmm_dep
 
@@ -247,6 +248,7 @@ if maintainer_mode
     include_directories: extra_include_dirs,
     cpp_args: glibmm_cpp_args,
     version: glibmm_libversion,
+    darwin_versions: macos_darwin_versions,
     dependencies: glibmm_build_dep,
     install: true,
   )
@@ -299,6 +301,7 @@ else # not maintainer_mode
     include_directories: extra_include_dirs,
     cpp_args: glibmm_cpp_args,
     version: glibmm_libversion,
+    darwin_versions: macos_darwin_versions,
     dependencies: glibmm_build_dep,
     install: true,
   )
diff --git a/meson.build b/meson.build
index 20ae62eb..4d2c13a6 100644
--- a/meson.build
+++ b/meson.build
@@ -30,7 +30,12 @@ libtool_soversion = [4, 0, 3]
 glibmm_libversion = '@0@.@1@.@2@'.format(
   libtool_soversion[0] - libtool_soversion[2],
   libtool_soversion[2],
-  libtool_soversion[1])
+  libtool_soversion[1]
+)
+macos_darwin_versions = [
+  libtool_soversion[0] + 1,
+  '@0@.@1@'.format(libtool_soversion[0] + 1, libtool_soversion[1])
+]
 
 # Use these instead of meson.source_root() and meson.build_root() in subdirectories.
 # source_root() and build_root() are not useful, if this is a subproject.