Process.warnump: precompute strings coderange

This both save time for when it will be eventually needed,
and avoid mutating heap pages after a potential fork.

process.c

@@ -8535,6 +8535,27 @@ static VALUE rb_mProcUID;
 static VALUE rb_mProcGID;
 static VALUE rb_mProcID_Syscall;
 
+
+static int
+proc_warmup_each_object(void *vstart, void *vend, size_t stride, void *data)
+{
+    VALUE v = (VALUE)vstart;
+    for (; v != (VALUE)vend; v += stride) {
+        switch (BUILTIN_TYPE(v)) {
+          case T_STRING:
+            // precompute the string coderange. This both save time for when it will be
+            // eventually needed, and avoid mutating heap pages after a potential fork.
+            rb_enc_str_coderange(v);
+            break;
+          default:
+            break;
+        }
+    }
+
+    return 0;
+}
+
+
 /*
  *  call-seq:
  *     Process.warmup    -> true
@@ -8563,6 +8584,9 @@ proc_warmup(VALUE _)
     RB_VM_LOCK_ENTER();
     rb_gc_prepare_heap();
     RB_VM_LOCK_LEAVE();
+
+    rb_objspace_each_objects(proc_warmup_each_object, NULL);
+
     return Qtrue;
 }
 

test/ruby/test_process.rb

@@ -2709,4 +2709,12 @@ def test_warmup_run_major_gc_and_compact
       assert_equal compact_count + 1, GC.stat(:compact_count)
     end;
   end
+
+  def test_warmup_precompute_string_coderange
+    obj = "a" * 12
+    obj.force_encoding(Encoding::BINARY)
+    assert_includes(ObjectSpace.dump(obj), '"coderange":"unknown"')
+    Process.warmup
+    assert_includes(ObjectSpace.dump(obj), '"coderange":"7bit"')
+  end
 end