Error with Mathematica 12.3.1 Apple ARM version

[RobR16]

Hello,
I think 12.3.1 was the first macOS Mathematica version with native ARM/Silicon support, and after upgrading to it I get the following error in a program that uses FindMathematica in its cmake-list:

"could NOT find Mathematica_WolframLibrary (missing: Mathematica_WolframLibrary_LIBRARY) (found version "6")
-- Could NOT find Mathematica (missing: Mathematica_WolframLibrary_LIBRARY) (found version "12.3.1")"

After looking in the cmakeCACHE file, I found that it did not find the Wolfram Runtime Library (correct path: "/Applications/Mathematica.app/Contents/SystemFiles/Libraries/MacOSX-ARM64/libWolframRTL.dylib" ),

and the cache file contains the entry
//Last value of Mathematica_SYSTEM_IDS.
Mathematica_SYSTEM_IDS_LAST:INTERNAL=MacOSX-x86-64

which I guess could be problematic. It seems like in most other relevant paths it correctly replaced MacOSX-x86-64 by /MacOSX-ARM64. I will try to fix it by myself, but if you could make FindMathematica compatible with the 12.3.1 version in a clean way, I guess it would be greatly appreciated by many.

[windfolgen]

Hello,
I have exactly the same problem with you and I don't know how to solve it. Is it OK to replace the wrong KEYs manually? Have you found a clean way to solve it? I really appreciate it if you or someone else could help.

[windfolgen]

I think I may find how to resolve this problem. The solution is simple: just add below syntax in the CMakeList.txt before compiling it
set(CMAKE_OSX_ARCHITECTURE arm64)
The reason may be that default value for CMAKE_OSX_ARCHITECTURE is null, so you should set it first. In the FindMathematica.cmake you can find the following macro
macro (_get_system_IDs _outSystemIDs)
if (WIN32 OR CYGWIN)
...
elseif (APPLE)
set (${_outSystemIDs} "")
if (CMAKE_OSX_ARCHITECTURES)
# determine System ID from specified architectures
...
else()
# determine System ID by checking endianness and pointer size
TEST_BIG_ENDIAN(_isBigEndian)
if (_isBigEndian)
...
else ()
if (CMAKE_SIZEOF_VOID_P EQUAL 8)
set (${_outSystemIDs} "MacOSX-x86-64")
else ()
set (${_outSystemIDs} "MacOSX-x86")
endif()
endif()
endif()
elseif (UNIX)
...
else()
...
endmacro(_get_system_IDs)
If you don't set CMAKE_OSX_ARCHITECTURES, then it will determine by checking endianness and pointer size. Since apple M1 is little endian, it will check CMAKE_SIZEOF_VOID_P and further determine the result. However, it only provide two choices "MacOSX-x86-64" and "MacOSX-x86". So this will give you a wrong value on a MacOSX-ARM64 machine. If CMAKE_OSX_ARCHITECTURES is set, this problem won't appear. I hope this can help explain why it may go wrong on apple ARM machine.