Merge pull request #11 from semgrep/nathan/domains_inherit_backtrace

feat: preserve `backtrace_enabled` between domains

This is a backport of ocaml#14416 , which fixes ocaml#14411 . This patch subsumes semgrep/semgrep-proprietary#5022 (since it makes the same fix but in the runtime rather than in our user code).

Author: dijkstracula

runtime/domain.c

@@ -742,9 +742,10 @@ static void domain_create(uintnat initial_minor_heap_wsize,
 
   domain_state->parser_trace = 0;
 
-  if (caml_params->backtrace_enabled) {
-    caml_record_backtraces(1);
-  }
+  bool bt_enabled = parent
+    ? parent->backtrace_active
+    : caml_params->backtrace_enabled;
+  caml_record_backtraces(bt_enabled);
 
 #ifndef NATIVE_CODE
   domain_state->external_raise = NULL;

stdlib/printexc.mli

@@ -74,6 +74,8 @@ val record_backtrace: bool -> unit
     on (if [b = true]) or off (if [b = false]).  Initially, backtraces
     are not recorded, unless the [b] flag is given to the program
     through the [OCAMLRUNPARAM] variable.
+    @before 5.3-semgrep Spawned domains' backtraces would not be recorded,
+    even if the parent had called [record_backtrace true].
     @since 3.11
 *)