Set DYLIB_COMPATIBILITY_VERSION to DYLIB_CURRENT_VERSION to match autotools

Autotools sets both versions to the same value, so Xcode and CMake need to match for the libraries to be compatible between the different builds.

See these for details:
https://github.com/libsdl-org/sdl12-compat/pull/207
https://github.com/libsdl-org/SDL/issues/2934
https://stackoverflow.com/questions/67055770/usage-of-current-version-and-compatibility-version-on-macos

CMakeLists.txt

@@ -123,7 +123,7 @@ 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")
+set(DYLIB_COMPATIBILITY_VERSION "${DYLIB_CURRENT_VERSION}")
 
 # This list holds all generated headers.
 # To avoid generating them twice, these are added to a dummy target on which all sdl targets depend.

Xcode/SDL/SDL.xcodeproj/project.pbxproj

@@ -9436,7 +9436,7 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEPLOYMENT_POSTPROCESSING = YES;
-				DYLIB_COMPATIBILITY_VERSION = 1.0.0;
+				DYLIB_COMPATIBILITY_VERSION = 2501.0.0;
 				DYLIB_CURRENT_VERSION = 2501.0.0;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
@@ -9521,7 +9521,7 @@
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				DEBUG_INFORMATION_FORMAT = dwarf;
-				DYLIB_COMPATIBILITY_VERSION = 1.0.0;
+				DYLIB_COMPATIBILITY_VERSION = 2501.0.0;
 				DYLIB_CURRENT_VERSION = 2501.0.0;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_STRICT_OBJC_MSGSEND = YES;

docs/release_checklist.md

@@ -22,8 +22,7 @@
         * 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` (?)
+        * set `DYLIB_COMPATIBILITY_VERSION` to the same value
 
 * Run test/versioning.sh to verify that everything is consistent
 

test/versioning.sh

@@ -130,15 +130,6 @@ fi
 
 # For simplicity this assumes we'll never break ABI before SDL 3.
 dylib_compat=$(sed -Ene 's/.*DYLIB_COMPATIBILITY_VERSION = (.*);$/\1/p' Xcode/SDL/SDL.xcodeproj/project.pbxproj)
-ref='1.0.0
-1.0.0'
-
-if [ "$ref" = "$dylib_compat" ]; then
-    ok "project.pbxproj DYLIB_COMPATIBILITY_VERSION is consistent"
-else
-    not_ok "project.pbxproj DYLIB_COMPATIBILITY_VERSION is inconsistent"
-fi
-
 dylib_cur=$(sed -Ene 's/.*DYLIB_CURRENT_VERSION = (.*);$/\1/p' Xcode/SDL/SDL.xcodeproj/project.pbxproj)
 
 case "$ref_minor" in
@@ -155,10 +146,16 @@ esac
 ref="${major}.${minor}.0
 ${major}.${minor}.0"
 
+if [ "$ref" = "$dylib_compat" ]; then
+    ok "project.pbxproj DYLIB_COMPATIBILITY_VERSION is consistent"
+else
+    not_ok "project.pbxproj DYLIB_COMPATIBILITY_VERSION is inconsistent, expected $ref, got $dylib_compat"
+fi
+
 if [ "$ref" = "$dylib_cur" ]; then
     ok "project.pbxproj DYLIB_CURRENT_VERSION is consistent"
 else
-    not_ok "project.pbxproj DYLIB_CURRENT_VERSION is inconsistent"
+    not_ok "project.pbxproj DYLIB_CURRENT_VERSION is inconsistent, expected $ref, got $dylib_cur"
 fi
 
 echo "1..$tests"