Wasm runtime: keep track of backtrace status

Author: vouillon

runtime/wasm/backtrace.wat

@@ -16,6 +16,10 @@
 ;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
 (module
+   (import "bindings" "backtrace_status"
+      (func $backtrace_status (result (ref eq))))
+   (import "bindings" "record_backtrace"
+      (func $record_backtrace (param (ref eq))))
    (import "fail" "caml_invalid_argument"
       (func $caml_invalid_argument (param (ref eq))))
 
@@ -28,7 +32,7 @@
 
    (func (export "caml_backtrace_status")
       (param (ref eq)) (result (ref eq))
-      (ref.i31 (i32.const 0)))
+      (call $backtrace_status))
 
    (func (export "caml_convert_raw_backtrace")
       (param (ref eq)) (result (ref eq))
@@ -62,6 +66,7 @@
       (param (ref eq)) (result (ref eq))
       (ref.i31 (i32.const 0)))
 
-   (func (export "caml_record_backtrace") (param (ref eq)) (result (ref eq))
+   (func (export "caml_record_backtrace") (param $b (ref eq)) (result (ref eq))
+      (call $record_backtrace (local.get $b))
       (ref.i31 (i32.const 0)))
 )

runtime/wasm/runtime.js

@@ -148,6 +148,13 @@
     return globalThis.jsoo_env?.[n];
   }
 
+  let record_backtrace_flag = 0;
+
+  for (const l of getenv("OCAMLRUNPARAM")?.split(",") || []) {
+    if (l === "b") record_backtrace_flag = 1;
+    if (l.startsWith("b=")) record_backtrace_flag = +!!+l[i].slice(2);
+  }
+
   function alloc_stat(s, large) {
     var kind;
     if (s.isFile()) {
@@ -464,6 +471,8 @@
     argv: () => (isNode ? process.argv.slice(1) : ["a.out"]),
     on_windows: +on_windows,
     getenv,
+    backtrace_status: () => record_backtrace_flag,
+    record_backtrace: (b) => (record_backtrace_flag = b),
     system: (c) => {
       var res = require("node:child_process").spawnSync(c, {
         shell: true,