Generator for missing Intel oneAPI Fortran library on macOS

Rationale

In trying to use Intel oneAPI Fortran on macOS, I recently found that versions greater than 2021.2 seem to not work. The bug presents at build time as:

ld: file not found: @rpath/for_mac_ftn_alloc.dylib for architecture x86_64

Investigations into the Fortran libraries in oneAPI show that this new library, for_mac_ftn_alloc.dylib, is wanted by oneAPI as of 2021.3 in libifcore.dylib and in libifcoremt.dylib. You can see this with otool:

❯ otool -L libifcore.dylib | grep for_mac
	@rpath/for_mac_ftn_alloc.dylib (compatibility version 1.0.0, current version 1.11.0, weak)
❯ otool -L libifcoremt.dylib | grep for_mac
	@rpath/for_mac_ftn_alloc.dylib (compatibility version 1.0.0, current version 1.11.0, weak)
❯ otool -l libifcore.dylib | less
libifcore.dylib:
Load command 0
      cmd LC_SEGMENT_64
  cmdsize 632
  segname __TEXT
...
Load command 8
      cmd LC_VERSION_MIN_MACOSX
  cmdsize 16
  version 10.11
      sdk 10.13
Load command 9
      cmd LC_SOURCE_VERSION
  cmdsize 16
  version 0.0
Load command 10
          cmd LC_LOAD_WEAK_DYLIB
      cmdsize 56
         name @rpath/for_mac_ftn_alloc.dylib (offset 24)
   time stamp 2 Wed Dec 31 19:00:02 1969
      current version 1.11.0
compatibility version 1.0.0
Load command 11
          cmd LC_LOAD_DYLIB
      cmdsize 48
         name @rpath/libimf.dylib (offset 24)
   time stamp 2 Wed Dec 31 19:00:02 1969
...

The problem is, there is no for_mac_ftn_alloc.dylib in oneAPI or anywhere else on my Mac. (It does not appear to be in gcc, Open MPI, Xcode, etc.)

But this does present us with a possible hack/workaround. The for_mac_ftn_alloc.dylib library is LC_LOAD_WEAK_DYLIB which, from my reading of how this works, means the library is allowed to not be present at run time. Obviously it's not allowed to be missing at build-time though.

Implementation

So, to work around this, a stub library was created. This library is very boring:

subroutine cws8vn9ud915dz907vl_()
end

It's essentially a "blank" library with a crazy procedure name that should never be used that we are creating only to satisfy the need at ld time.

How to build

To build, load up your Intel and run:

❯ cmake --preset default && cmake --build --preset default
-- The Fortran compiler identification is Intel 2021.5.0.20211109
-- Detecting Fortran compiler ABI info
-- Detecting Fortran compiler ABI info - done
-- Check for working Fortran compiler: /opt/intel/oneapi/compiler/2022.0.0/mac/bin/intel64/ifort - skipped
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/mathomp4/intellibhack/build
Scanning dependencies of target for_mac_ftn_alloc
[ 50%] Building Fortran object CMakeFiles/for_mac_ftn_alloc.dir/stub.F90.o
[100%] Linking Fortran shared library for_mac_ftn_alloc.dylib
[100%] Built target for_mac_ftn_alloc

How to install

Once it builds, you should have a for_mac_ftn_alloc.dylib library in the build directory. What you'll want to copy that file into the /opt/intel/oneapi/compiler/<version>/mac/compiler/lib directory.

NOTE: I'm guessing you should build the library with the exact same version of Intel oneAPI that you need the library for. I'm not good at shared object libraries, etc. and with otool I see some hardcoded paths inside it.