sml: unable to determine operating system in emacs but works fine in terminal

Question

I succeeded in installing smlnj on my MAC OS 10.14 Mojave. It works just fine in terminal. Then, I got into trouble with sml package installation in emacs. When I type something in a .sml file, color and indents are all correct. However, when I do C-c C-s and hit enter, it shows, "sml: unable to determine architecture/operating system," and thus I am not able to do anything in this buffer, such as type 1+1; or anything else. Is there any hint on how to get around this issue? I've been stuck here the whole day. Thanks in advance!

Answer 1

This appears to be a problem in SML/NJ's run-time system:

I've only got the source code for 110.77, and I don't know what version of SML/NJ you are running, but here's how I go through the debug process and what you can do afterwards:

$ ack "unable to determine arch" smlnj
config/_heap2exec
24: die "unable to determine architecture/operating system"

config/_link-sml
47:  echo "$CMD: unable to determine architecture/operating system"

config/_run-sml
62:  echo "$CMD: unable to determine architecture/operating system"

Perhaps Emacs does not export the proper environment variables for SML/NJ's binary to properly detect the operating system. Digging into config/_run-sml, this looks like the code that causes the error message:

ARCH_N_OPSYS=`"$BIN_DIR/.arch-n-opsys"`
if [ "$?" != "0" ]; then
  echo "$CMD: unable to determine architecture/operating system"
  exit 1
fi
eval $ARCH_N_OPSYS

Inside config/_arch-n-opsys there's a switch statement for MacOS:

Darwin)
  case `uname -p` in
    powerpc)
  ARCH=ppc
  case `uname -r` in
    9*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.5 Leopard
    *) exit 1;;
  esac;;
    i386) ARCH=x86;
  case `uname -r` in
    9*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.5 Leopard
    10*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.6 Snow Leopard
    11*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.7 Lion
    12*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.8 Mountain Lion
    13*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.9 Mavericks
    14*) OPSYS=darwin;  HEAP_OPSYS=darwin ;; # MacOS X 10.10 Yosemite
    *) exit 1;;
  esac;;

The shell script .arch-n-opsys is one that determines the operating system you're using. So it seems that SML/NJ 110.77's run-time system does not detect MacOS beyond 10.10. Why this is not a problem outside of Emacs I'm not sure.

You could try and run the program from within Emacs via M-x shell RET and type:

cd /usr/lib/smlnj/bin
ls -a
./.arch-n-opsys

I suspect that you can fix this problem locally if you replace this .arch-n-opsys binary with a tiny shell script that hardcodes your preferred options, which are probably:

#!/bin/sh
echo "ARCH=darwin; OPSYS=darwin; HEAP_SUFFIX=darwin-darwin"

If that doesn't work, maybe some of the other options that the original .arch-n-opsys shell script lists will work.

---

Only in case you're interested in fixing the problem for others:

1. Find out if the latest version, 110.85, supports MacOS > 10.10.

2. If not, write to the email at the bottom of smlnj.org and link to this StackOverflow post and say what uname -r does on your system, or supply a diff that works for your system in particular.