Dune cache causing `dune exec` process to die

[tzemanovic]

Enabling dune cache seems to affect dune exec command. When the executable needs to be rebuilt, dune cache causes the process to die on the first run. The process runs fine on a subsequent run.

Reproduction

1. enable dune cache with ~/.config/dune/config containing:

   (lang dune 2.6.2)
   (cache enabled)

2. run dune exec x.exe and exit
3. make a change in ocaml source code to force compilation
4. run dune exec x.exe again, the executable dies immediately with status code 137
5. if we run dune exec x.exe again, it runs fine

Specifications

• Version of dune (output of dune --version): 2.6.2
• Version of ocaml (output of ocamlc --version): 4.09.1
• Operating system (distribution and version): Darwin 19.5.0 Darwin Kernel Version 19.5.0: Tue May 26 20:41:44 PDT 2020; root:xnu-6153.121.2~2/RELEASE_X86_64 x86_64

Additional information

• Link to gist with verbose output (run dune with the --verbose flag): The output of the command when the executable dies: https://gist.github.com/tzemanovic/c50f1846b883bad34280982254f1ff9c

[mefyl]

I can't reproduce with a minimal test:

$ dune --version
2.6.2
$ cat dune-project 
(lang dune 2.6)
$ cat
$ cat dune 
(executable
 (name main))
$ cat main.ml
let () =
  print_endline "1"
$ DUNE_CACHE=enabled dune exec ./main.exe
1                    
$ sed -i s/1/2/ main.ml 
$ DUNE_CACHE=enabled dune exec ./main.exe
2                    

Can you please check I didn't miss something from your instructions ? If not, is there any way to get the actual setup that exhibits the issue ?

[rgrinberg]

@tzemanovic please re-open if you're still able to repro.