Openbsd fails to build ocaml 5.20, 4.14.2 etc. on a fresh install

[MarcCoquand]

If your issue concerns a package not building, please report to
https://github.com/ocaml/opam-repository/issues or to the package maintainer
unless you are confident it is an issue in the opam tool itself.
If your issue concerns failures with the opam.ocaml.org website, please report to
https://github.com/ocaml/infrastructure/issues

# opam config report
# opam-version      2.0.10 
# self-upgrade      no
# system            arch=x86_64 os=openbsd os-distribution=openbsd os-version=7.5
# solver            builtin-mccs+glpk
# install-criteria  -removed,-count[version-lag,request],-count[version-lag,changed],-changed
# upgrade-criteria  -removed,-count[version-lag,solution],-new
# jobs              1
# repositories      1 (http) (default repo at 175a8ca8)
# pinned            0
# current-switch    default

opam init and opam switch create 4.14.2 fails on a fresh Openbsd install.

 #=== ERROR while compiling ocaml-base-compiler.4.14.2 =========================#                                             
# context     2.0.10 | openbsd/x86_64 |  | https://opam.ocaml.org#175a8ca8                                                   
# path        ~/.opam/4.14.2/.opam-switch/build/ocaml-base-compiler.4.14.2                                                   
# command     /usr/local/bin/gmake -j1                                                                                       
# exit-code   2                                                                                                              
# env-file    ~/.opam/log/ocaml-base-compiler-19142-1872ec.env                                                               
# output-file ~/.opam/log/ocaml-base-compiler-19142-1872ec.out                                                              
### output ###                                                                                                              
# [...]                                                                                                                     
# ../../ocamlc.opt -g -nostdlib -I ../../stdlib -c -strict-sequence -principal -                                             absname -w +a-4-9-40-41-42-44-45-48-66-70 -warn-error +A -bin-annot -safe-string                                              -strict-formats -I byte extract_crc.ml
# ../../ocamlc.opt -g -nostdlib -I ../../stdlib -o extract_crc dynlink.cma byte/dynlink_compilerlibs.cmo extract_crc.cmo
# gmake[4]: *** [Makefile:239: extract_crc] Segmentation fault (core dumped)
# gmake[4]: *** Deleting file 'extract_crc'
# gmake[4]: Leaving directory '/home/mccd/.opam/4.14.2/.opam-switch/build/ocaml-base-compiler.4.14.2/otherlibs/dynlink'
# gmake[3]: *** [Makefile:34: all] Error 2
# gmake[3]: Leaving directory '/home/mccd/.opam/4.14.2/.opam-switch/build/ocaml-base-compiler.4.14.2/otherlibs'
# gmake[2]: *** [Makefile:962: otherlibraries] Error 2
# gmake[2]: Leaving directory '/home/mccd/.opam/4.14.2/.opam-switch/build/ocaml-base-compiler.4.14.2'
# gmake[1]: *** [Makefile:253: opt.opt] Error 2
# gmake[1]: Leaving directory '/home/mccd/.opam/4.14.2/.opam-switch/build/ocaml-base-compiler.4.14.2'
# gmake: *** [Makefile:314: world.opt] Error 2

[kit-ty-kate]

I'm unable to reproduce with a similar setup (OpenBSD 7.5 / x86_64), for me the compiler compiled just fine.
And while your version of opam is extremely outdated, it is not failing in opam but during the compilation so it is unrelated to opam itself.

Are you able to reproduce if you try to compile the compiler by hand? And if so are you able to get a stacktrace to be able to see where it's segfaulting?

[avsm]

You'll need to apply ocaml/ocaml#13023 -- you almost certainly have a modern Intel CPU that's enforcing control flow integrity.