Restore JL_NOTSAFEPOINT in jl_stderr_obj (#56407)

This is not a function we're really using, but it's used in the
embedding examples, so I'm sure somebody would complain if I deleted it
or made it a safepoint, so let's just give the same best-effort result
as before.

src/julia.h

@@ -1854,6 +1854,7 @@ JL_DLLEXPORT jl_sym_t *jl_tagged_gensym(const char *str, size_t len);
 JL_DLLEXPORT jl_sym_t *jl_get_root_symbol(void);
 JL_DLLEXPORT jl_value_t *jl_get_binding_value(jl_binding_t *b JL_PROPAGATES_ROOT);
 JL_DLLEXPORT jl_value_t *jl_get_binding_value_if_const(jl_binding_t *b JL_PROPAGATES_ROOT);
+JL_DLLEXPORT jl_value_t *jl_get_binding_value_if_resolved(jl_binding_t *b JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT;
 JL_DLLEXPORT jl_value_t *jl_get_binding_value_if_resolved_and_const(jl_binding_t *b JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT;
 JL_DLLEXPORT jl_value_t *jl_declare_const_gf(jl_binding_t *b, jl_module_t *mod, jl_sym_t *name);
 JL_DLLEXPORT jl_method_t *jl_method_def(jl_svec_t *argdata, jl_methtable_t *mt, jl_code_info_t *f, jl_module_t *module);

src/module.c

@@ -360,6 +360,28 @@ JL_DLLEXPORT jl_value_t *jl_get_binding_value_if_resolved_and_const(jl_binding_t
     return decode_restriction_value(pku);
 }
 
+JL_DLLEXPORT jl_value_t *jl_get_binding_value_if_resolved(jl_binding_t *b)
+{
+    // Unlike jl_get_binding_value this doesn't try to allocate new binding partitions if they
+    // don't already exist, making this JL_NOTSAFEPOINT.
+    if (!b)
+        return NULL;
+    jl_binding_partition_t *bpart = jl_atomic_load_relaxed(&b->partitions);
+    if (!bpart)
+        return NULL;
+    size_t max_world = jl_atomic_load_relaxed(&bpart->max_world);
+    if (bpart->min_world > jl_current_task->world_age || jl_current_task->world_age > max_world)
+        return NULL;
+    jl_ptr_kind_union_t pku = jl_atomic_load_relaxed(&bpart->restriction);
+    if (jl_bkind_is_some_guard(decode_restriction_kind(pku)))
+        return NULL;
+    if (jl_bkind_is_some_import(decode_restriction_kind(pku)))
+        return NULL;
+    if (jl_bkind_is_some_constant(decode_restriction_kind(pku)))
+        return decode_restriction_value(pku);
+    return jl_atomic_load_relaxed(&b->value);
+}
+
 JL_DLLEXPORT jl_value_t *jl_bpart_get_restriction_value(jl_binding_partition_t *bpart)
 {
     jl_ptr_kind_union_t pku = jl_atomic_load_relaxed(&bpart->restriction);

src/rtutils.c

@@ -567,7 +567,7 @@ JL_DLLEXPORT jl_value_t *jl_stderr_obj(void) JL_NOTSAFEPOINT
     if (jl_base_module == NULL)
         return NULL;
     jl_binding_t *stderr_obj = jl_get_module_binding(jl_base_module, jl_symbol("stderr"), 0);
-    return stderr_obj ? jl_get_binding_value(stderr_obj) : NULL;
+    return stderr_obj ? jl_get_binding_value_if_resolved(stderr_obj) : NULL;
 }
 
 // toys for debugging ---------------------------------------------------------