Using janet_dobytes or janet_dostring with os/ commands causes block to fail to evaluate/return

[ahungry]

Related to: janet-lang/circlet#17 - I have found a similar issue in my bespoke web server implementation - however, it can be distilled down to the following small snippet fail case:

// gcc -Wall -I./amalg ./amalg/janet.c ./src/janet-os-fail.c -o test.bin -lm
#include <janet.h>
#include <string.h>

char *
janet_stuff ()
{
  JanetTable *env;

  janet_init ();
  env = janet_core_env (NULL);

  Janet ret;
  int h = janet_gclock ();

  // This will fail
  // janet_dostring (env, "(do (os/shell \"whoami\") \"bob\")", "fake", &ret);

  // This will succeed
  janet_dostring (env, "(do \"bob\")", "fake", &ret);

  const unsigned char *result;

  if (janet_checktype (ret, JANET_STRING))
    {
      result = janet_unwrap_string (ret);
    }
  else
    {
      fprintf (stderr, "The string was not returned, woops.");
      result = (uint8_t *) "FAILURE";
    }

  janet_gcunlock (h);
  janet_deinit ();

  return (char *) result;
}

int
main (int argc, char *argv[])
{
  char *res = janet_stuff ();

  fprintf (stdout, res);

  return 0;
}

// Sample output
/* ❯ gcc -Wall -I./amalg ./amalg/janet.c ./src/janet-os-fail.c -o test.bin -lm */
/* ❯ ./test.bin */
/* The string was not returned, woops.FAILURE% */
/* mcarter */
/* ❯ gcc -Wall -I./amalg ./amalg/janet.c ./src/janet-os-fail.c -o test.bin -lm */
/* ❯ ./test.bin */
/* bob% */

To reproduce the failure, simply swap the janet_dostring() lines so you execute the one with the os/shell call in it. It will not finish block evaluation and return the string "bob" as it should.

Compare to a valid Janet in the REPL, which will reproduce the behavior as expected.

(do (os/shell "whoami") "bob")
mcarter
"bob"

FWIW, this is under Janet 1.20 built from the tag

[ahungry]

Also - it occurs with or without the gclock, so it doesn't appear to be some obscure issue with having gc locked while os/ is executed.

[ahungry]

Interestingly enough, if I wrap the os/ call in an (ev/spawn-thread), the problem goes away.

[bakpakin]

Functions that use the event loop must have a call to janet_loop to run the event loop to completion. I guess the next question would be, should janet_dobytes and janet_dostring call janet_loop under the hood - they predate the event loop so currently they don't.