Add SOVERSION for the C++ libraries

CMakeLists.txt

@@ -119,6 +119,31 @@ else()
     endif()
 endif()
 
+# Set the SO version. The SO version must be incremented every time a change
+# occurs to the ABI that causes a backward incompatibility. Such changes
+# include, exhaustively:
+#
+# * a change to struct or class layout
+# * enum changes that would cause a renumbering of previously published enums
+# * a removal of a struct, class, enumeration, or function
+# * a change in parameters to a free standing function
+# * a removal of a global variable
+#
+# OTIO currently designates the minor version number for breaking changes,
+# e.g. v0.15, v0.16.0, v0.17.0, accordingly the SO version will be incremented
+# to match. SO version must be monotically increasing, so the ABI version
+# should be computed as: major * 100 + revision. The third digit will never
+# implicate an ABI version change. So for example, the following OTIO versions
+# would map to these ABI versions:
+#
+# * v0.18.0 - 18
+# * v0.19.0 - 19
+# * v0.19.1 - 19 # No ABI changes with minor version changes
+# * v1.0.0 - 100
+# * v1.1.0 - 101
+#
+math(EXPR OTIO_SOVERSION "${OTIO_VERSION_MAJOR} * 100 + ${OTIO_VERSION_MINOR}")
+
 set(OTIO_RESOLVED_CXX_INSTALL_DIR "${CMAKE_INSTALL_PREFIX}")
 
 if(OTIO_CXX_INSTALL)

src/opentime/CMakeLists.txt

@@ -24,6 +24,12 @@ set_target_properties(opentime PROPERTIES
     POSITION_INDEPENDENT_CODE TRUE
     WINDOWS_EXPORT_ALL_SYMBOLS true)
 
+if(BUILD_SHARED_LIBS)
+    set_target_properties(opentime PROPERTIES
+        SOVERSION ${OTIO_SOVERSION}
+        VERSION ${OTIO_VERSION})
+endif()
+
 if(APPLE)
     set_target_properties(opentime PROPERTIES 
         INSTALL_NAME_DIR "@loader_path"

src/opentimelineio/CMakeLists.txt

@@ -98,6 +98,12 @@ set_target_properties(opentimelineio PROPERTIES
     POSITION_INDEPENDENT_CODE TRUE
     WINDOWS_EXPORT_ALL_SYMBOLS true)
 
+if(BUILD_SHARED_LIBS)
+    set_target_properties(opentimelineio PROPERTIES
+        SOVERSION ${OTIO_SOVERSION}
+        VERSION ${OTIO_VERSION})
+endif()
+
 if(APPLE)
     set_target_properties(opentimelineio PROPERTIES 
         INSTALL_NAME_DIR "@loader_path"