How to build SML/NJ executable on Mac - macos

Question

I have an SML/NJ program that I can run as a heap image, and I want to create a standalone executable binary. However, the heap2exec tool in SML/NJ 110.73 always yields errors for me.
I created my heap image tigerc.x86-darwin via the following:
ml-build sources.cm Main.main tigerc
I can run my program fine using the heap image via
sml #SMLload=tigerc.x86-darwin
I should be able to create the standalone binary via
heap2exec tigerc.x86-darwin tigerc
but that generates the error
ld: warning: -macosx_version_min not specificed, assuming 10.7
ld: warning: ignoring file tigerc.o, file was built for unsupported file format
which is not the architecture being linked (i386)
I looked at the heap2exec shell script, and the key lines (variable-expanded) do the following:
heap2asm "$heapfile" "$execfile".s
cc -c -o "$execfile".o "$execfile".s
ld -o "$execfile" ${RUNX} "$execfile".o
When I run these steps individually, the cc command generates an x86_64 .o file, but the ld command is trying to link an i386 executable. So I need to convince the cc command to generate an i386 .o file as well.
Is there a way to set an environment variable to get cc to build i386 instead of x86_84? (ARCH doesn't do the trick, by the way — it's already set to i386.)
Or is there another workaround to get heap2exec to generate the right architecture?

Answer 1

Try adding CFLAGS=-m32 as an environment variable. That's the standard way to force it to build a 32-bit object file.
I know you're asking specifically about SML/NJ, but MLton has 64-bit support and makes this kind of task really easy. You might thank yourself later if you're in a position to use it to generate executable binaries instead.