initialize standard pipes in vm init to keep them rooted

src/file.c

@@ -14,18 +14,12 @@ Ut userdata_file = {
 // clang-format on
 
 I prim_file_stdout(Vm *vm) {
-  static O stdout_object = NIL;
-  if (stdout_object == NIL)
-    stdout_object = userdata_make(vm, (void *)stdout, &userdata_file);
-  vm_push(vm, stdout_object);
+  vm_push(vm, vm->stdout);
   return 0;
 }
 
 I prim_file_stderr(Vm *vm) {
-  static O stderr_object = NIL;
-  if (stderr_object == NIL)
-    stderr_object = userdata_make(vm, (void *)stderr, &userdata_file);
-  vm_push(vm, stderr_object);
+  vm_push(vm, vm->stderr);
   return 0;
 }
 

src/vm.c

@@ -7,8 +7,9 @@
 #include "dictionary.h"
 #include "gc.h"
 #include "object.h"
-#include "print.h"
-#include "src/primitive.h"
+#include "primitive.h"
+#include "userdata.h"
+#include "file.h"
 #include "string.h"
 #include "vm.h"
 
@@ -47,6 +48,14 @@ V vm_init(Vm *vm) {
     gc_addroot(&vm->gc, &vm->stack[i]);
     gc_addroot(&vm->gc, &vm->tstack[i]);
   }
+
+  vm->stdin = userdata_make(vm, (void *)stdin, &userdata_file);
+  vm->stdout = userdata_make(vm, (void *)stdout, &userdata_file);
+  vm->stderr = userdata_make(vm, (void *)stderr, &userdata_file);
+
+  gc_addroot(&vm->gc, &vm->stdin);
+  gc_addroot(&vm->gc, &vm->stdout);
+  gc_addroot(&vm->gc, &vm->stderr);
 }
 
 V vm_deinit(Vm *vm) {

src/vm.h

@@ -68,6 +68,9 @@ typedef struct Vm {
   Dt *dictionary;
   Ar arena;
   jmp_buf error;
+
+  // These objects need to stay as roots!
+  O stdin, stdout, stderr;
 } Vm;
 
 enum {