kc3-lang/SDL

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 718d38f..ca85714 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -60,12 +60,7 @@ include(${SDL2_SOURCE_DIR}/cmake/sdlchecks.cmake)
 set(SDL_MAJOR_VERSION 2)
 set(SDL_MINOR_VERSION 23)
 set(SDL_MICRO_VERSION 0)
-set(SDL_INTERFACE_AGE 0)
-set(SDL_BINARY_AGE 23)
 set(SDL_VERSION "${SDL_MAJOR_VERSION}.${SDL_MINOR_VERSION}.${SDL_MICRO_VERSION}")
-# the following should match the versions in Xcode project file:
-set(DYLIB_CURRENT_VERSION 24.0.0)
-set(DYLIB_COMPATIBILITY_VERSION 1.0.0)
 
 # Set defaults preventing destination file conflicts
 set(SDL_CMAKE_DEBUG_POSTFIX "d"
@@ -74,9 +69,22 @@ set(SDL_CMAKE_DEBUG_POSTFIX "d"
 mark_as_advanced(CMAKE_IMPORT_LIBRARY_SUFFIX SDL_CMAKE_DEBUG_POSTFIX)
 
 # Calculate a libtool-like version number
-math(EXPR LT_CURRENT "${SDL_MINOR_VERSION} - ${SDL_INTERFACE_AGE}")
+math(EXPR SDL_BINARY_AGE "${SDL_MINOR_VERSION} * 100 + ${SDL_MICRO_VERSION}")
+if(SDL_MINOR_VERSION MATCHES "[02468]$")
+    # Stable branch, 2.24.1 -> libSDL2-2.0.so.0.2400.1
+    set(SDL_INTERFACE_AGE ${SDL_MICRO_VERSION})
+else()
+    # Development branch, 2.23.1 -> libSDL2-2.0.so.0.2301.0
+    set(SDL_INTERFACE_AGE 0)
+endif()
+
+# Increment this if there is an incompatible change - but if that happens,
+# we should rename the library from SDL2 to SDL3, at which point this would
+# reset to 0 anyway.
+set(LT_MAJOR "0")
+
 math(EXPR LT_AGE "${SDL_BINARY_AGE} - ${SDL_INTERFACE_AGE}")
-math(EXPR LT_MAJOR "${LT_CURRENT}- ${LT_AGE}")
+math(EXPR LT_CURRENT "${LT_MAJOR} + ${LT_AGE}")
 set(LT_REVISION "${SDL_INTERFACE_AGE}")
 # For historical reasons, the library name redundantly includes the major
 # version twice: libSDL2-2.0.so.0.
@@ -85,6 +93,16 @@ set(LT_REVISION "${SDL_INTERFACE_AGE}")
 set(LT_RELEASE "2.0")
 set(LT_VERSION "${LT_MAJOR}.${LT_AGE}.${LT_REVISION}")
 
+# The following should match the versions in the Xcode project file.
+# Each version is 1 higher than you might expect, for compatibility
+# with libtool: macOS ABI versioning is 1-based, unlike other platforms
+# which are normally 0-based.
+math(EXPR DYLIB_CURRENT_VERSION_MAJOR "${LT_MAJOR} + ${LT_AGE} + 1")
+math(EXPR DYLIB_CURRENT_VERSION_MINOR "${LT_REVISION}")
+math(EXPR DYLIB_COMPAT_VERSION_MAJOR "${LT_MAJOR} + 1")
+set(DYLIB_CURRENT_VERSION "${DYLIB_CURRENT_VERSION_MAJOR}.${DYLIB_CURRENT_VERSION_MINOR}.0")
+set(DYLIB_COMPATIBILITY_VERSION "${DYLIB_COMPAT_VERSION_MAJOR}.0.0")
+
 #message(STATUS "${LT_VERSION} :: ${LT_AGE} :: ${LT_REVISION} :: ${LT_CURRENT} :: ${LT_RELEASE}")
 
 # General settings & flags
diff --git a/Xcode/SDL/SDL.xcodeproj/project.pbxproj b/Xcode/SDL/SDL.xcodeproj/project.pbxproj
index 6b23c9d..efdc40c 100644
--- a/Xcode/SDL/SDL.xcodeproj/project.pbxproj
+++ b/Xcode/SDL/SDL.xcodeproj/project.pbxproj
@@ -9208,7 +9208,7 @@
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEPLOYMENT_POSTPROCESSING = YES;
 				DYLIB_COMPATIBILITY_VERSION = 1.0.0;
-				DYLIB_CURRENT_VERSION = 24.0.0;
+				DYLIB_CURRENT_VERSION = 2301.0.0;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_ALTIVEC_EXTENSIONS = YES;
@@ -9292,7 +9292,7 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DYLIB_COMPATIBILITY_VERSION = 1.0.0;
-				DYLIB_CURRENT_VERSION = 24.0.0;
+				DYLIB_CURRENT_VERSION = 2301.0.0;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				ENABLE_TESTABILITY = YES;
diff --git a/configure.ac b/configure.ac
index 27c9316..4cab718 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,10 +14,17 @@ dnl Set various version strings - taken gratefully from the GTk sources
 SDL_MAJOR_VERSION=2
 SDL_MINOR_VERSION=23
 SDL_MICRO_VERSION=0
-SDL_INTERFACE_AGE=0
-SDL_BINARY_AGE=23
 SDL_VERSION=$SDL_MAJOR_VERSION.$SDL_MINOR_VERSION.$SDL_MICRO_VERSION
 
+SDL_BINARY_AGE=`expr $SDL_MINOR_VERSION \* 100 + $SDL_MICRO_VERSION`
+AS_CASE(["$SDL_MINOR_VERSION"],
+  [*[02468]],
+    dnl Stable branch, 2.24.1 -> libSDL2-2.0.so.0.2400.1
+    [SDL_INTERFACE_AGE="$SDL_MICRO_VERSION"],
+  [*],
+    dnl Development branch, 2.23.1 -> libSDL2-2.0.so.0.2301.0
+    [SDL_INTERFACE_AGE=0])
+
 AC_SUBST(SDL_MAJOR_VERSION)
 AC_SUBST(SDL_MINOR_VERSION)
 AC_SUBST(SDL_MICRO_VERSION)
@@ -33,9 +40,13 @@ LT_LANG([Windows Resource])
 # version twice: libSDL2-2.0.so.0.
 # TODO: in SDL 3, stop using -release, which will simplify it to libSDL3.so.0
 LT_RELEASE=2.0
-LT_CURRENT=`expr $SDL_MINOR_VERSION - $SDL_INTERFACE_AGE`
-LT_REVISION=$SDL_INTERFACE_AGE
+# Increment this if there is an incompatible change - but if that happens,
+# we should rename the library from SDL2 to SDL3, at which point this would
+# reset to 0 anyway.
+LT_MAJOR=0
 LT_AGE=`expr $SDL_BINARY_AGE - $SDL_INTERFACE_AGE`
+LT_CURRENT=`expr $LT_MAJOR + $LT_AGE`
+LT_REVISION=$SDL_INTERFACE_AGE
 m4_pattern_allow([^LT_])
 
 AC_SUBST(LT_RELEASE)
diff --git a/docs/release_checklist.md b/docs/release_checklist.md
index 2d4c5f9..d7e9c0c 100644
--- a/docs/release_checklist.md
+++ b/docs/release_checklist.md
@@ -17,14 +17,10 @@
 
 * Bump ABI version information
 
-    * `configure.ac`: `CMakeLists.txt`: `SDL_INTERFACE_AGE`, `SDL_BINARY_AGE`
-        * `SDL_BINARY_AGE += 1`
-        * set `SDL_INTERFACE_AGE` to 0
-        * if backwards compatibility has been broken,
-            set both `SDL_BINARY_AGE` and `SDL_INTERFACE_AGE` to 0
-    * `Xcode/SDL/SDL.xcodeproj/project.pbxproj`: `DYLIB_CURRENT_VERSION`,
-        `DYLIB_COMPATIBILITY_VERSION`
-        * increment first number in `DYLIB_CURRENT_VERSION`
+    * `CMakeLists.txt`, `Xcode/SDL/SDL.xcodeproj/project.pbxproj`:
+        `DYLIB_CURRENT_VERSION`, `DYLIB_COMPATIBILITY_VERSION`
+        * set first number in `DYLIB_CURRENT_VERSION` to
+            (100 * *minor*) + 1
         * set second number in `DYLIB_CURRENT_VERSION` to 0
         * if backwards compatibility has been broken,
             increase `DYLIB_COMPATIBILITY_VERSION` (?)
@@ -45,12 +41,9 @@
 
 * Bump ABI version information
 
-    * `configure.ac`: `CMakeLists.txt`: `SDL_INTERFACE_AGE`, `SDL_BINARY_AGE`
-        * `SDL_INTERFACE_AGE += 1`
-        * `SDL_BINARY_AGE += 1`
-    * `Xcode/SDL/SDL.xcodeproj/project.pbxproj`: `DYLIB_CURRENT_VERSION`,
-        `DYLIB_COMPATIBILITY_VERSION`
-        * increment second number in `DYLIB_CURRENT_VERSION`
+    * `CMakeLists.txt`, `Xcode/SDL/SDL.xcodeproj/project.pbxproj`:
+        `DYLIB_CURRENT_VERSION`, `DYLIB_COMPATIBILITY_VERSION`
+        * set second number in `DYLIB_CURRENT_VERSION` to *patchlevel*
 
 * Regenerate `configure`
 
@@ -77,8 +70,13 @@
 
 * Bump ABI version information
 
-    * Same places as listed above
-    * Assume that the next feature release will contain new API/ABI
+    * `CMakeLists.txt`, `Xcode/SDL/SDL.xcodeproj/project.pbxproj`:
+        `DYLIB_CURRENT_VERSION`, `DYLIB_COMPATIBILITY_VERSION`
+        * set first number in `DYLIB_CURRENT_VERSION` to
+            (100 * *minor*) + *patchlevel* + 1
+        * set second number in `DYLIB_CURRENT_VERSION` to 0
+        * if backwards compatibility has been broken,
+            increase `DYLIB_COMPATIBILITY_VERSION` (?)
 
 * Regenerate `configure`
 
diff --git a/src/SDL.c b/src/SDL.c
index 47ce674..a65d9c5 100644
--- a/src/SDL.c
+++ b/src/SDL.c
@@ -80,13 +80,8 @@ SDL_COMPILE_TIME_ASSERT(SDL_MINOR_VERSION_min, SDL_MINOR_VERSION >= 0);
 SDL_COMPILE_TIME_ASSERT(SDL_MINOR_VERSION_max, SDL_MINOR_VERSION <= 255);
 
 SDL_COMPILE_TIME_ASSERT(SDL_PATCHLEVEL_min, SDL_PATCHLEVEL >= 0);
-#if SDL_MAJOR_VERSION < 3
-/* Limited by its encoding in SDL_VERSIONNUM */
+/* Limited by its encoding in SDL_VERSIONNUM and in the ABI versions */
 SDL_COMPILE_TIME_ASSERT(SDL_PATCHLEVEL_max, SDL_PATCHLEVEL <= 99);
-#else
-/* Limited only by the need to fit in SDL_version */
-SDL_COMPILE_TIME_ASSERT(SDL_PATCHLEVEL_max, SDL_PATCHLEVEL <= 255);
-#endif
 
 /* This is not declared in any header, although it is shared between some
     parts of SDL, because we don't want anything calling it without an