CMake: Fix detection of Xcode version

Legacy code did not take into account the fact that major version can
be two digits. This was causing "Xcode 11.4" to be detected as "11.".

1 files changed, 18 insertions, 2 deletions

diff --git a/build_files/cmake/platform/platform_apple_xcode.cmake b/build_files/cmake/platform/platform_apple_xcode.cmake
index e42928328f3..6371bd9b288 100644
--- a/build_files/cmake/platform/platform_apple_xcode.cmake
+++ b/build_files/cmake/platform/platform_apple_xcode.cmake
@@ -68,10 +68,26 @@ if(${CMAKE_GENERATOR} MATCHES "Xcode")
     set(CMAKE_XCODE_ATTRIBUTE_GCC_VERSION "com.apple.compilers.llvmgcc42")
     message(STATUS "Setting compiler to: " ${CMAKE_XCODE_ATTRIBUTE_GCC_VERSION})
   endif()
-else() # unix makefile generator does not fill XCODE_VERSION var, so we get it with a command
+else()
+  # Unix makefile generator does not fill XCODE_VERSION var, so we get it with a command.
+  # Note that `xcodebuild -version` gives output in two lines: first line will include
+  # Xcode version, second one will include build number. We are only interested in the
+  # former one. Here is an example of the output:
+  #   Xcode 11.4
+  #   Build version 11E146
+  # The expected XCODE_VERSION in this case is 11.4.
+
   execute_process(COMMAND xcodebuild -version OUTPUT_VARIABLE XCODE_VERS_BUILD_NR)
-  string(SUBSTRING "${XCODE_VERS_BUILD_NR}" 6 3 XCODE_VERSION) # truncate away build-nr
+
+  # Convert output to a single line by replacling newlines with spaces.
+  # This is needed because regex replace can not operate through the newline character
+  # and applies substitutions for each individual lines.
+  string(REPLACE "\n" " " XCODE_VERS_BUILD_NR_SINGLE_LINE "${XCODE_VERS_BUILD_NR}")
+
+  string(REGEX REPLACE "(.*)Xcode ([0-9\\.]+).*" "\\2" XCODE_VERSION "${XCODE_VERS_BUILD_NR_SINGLE_LINE}")
+
   unset(XCODE_VERS_BUILD_NR)
+  unset(XCODE_VERS_BUILD_NR_SINGLE_LINE)
 endif()
 
 message(STATUS "Detected OS X ${OSX_SYSTEM} and Xcode ${XCODE_VERSION} at ${XCODE_BUNDLE}")