Change: native methods are provided with retval argument.

Previously, native methods were expected to return
their retval using vm->retval.  This caused problem in the part
(1aa137411b09, 293fe42c5e1c) because vm->retval can be overwritten
unexpectedly as a side-effect of operations like ToString(), ToNumber().

The fix is to never used a global retval. Instead methods
are provided with a retval argument to store their retval value.

As a part of the change, retval and exception values are split.
The normal value is returned in the retval argument.
The exception value is thrown by njs_vm_throw() or njs_vm_error().
The exception value can be acquired using njs_vm_exception_get().

1 files changed, 19 insertions, 7 deletions

diff --git a/nginx/ngx_js.c b/nginx/ngx_js.c
index b90dafa6..2b5be2ce 100644
--- a/nginx/ngx_js.c
+++ b/nginx/ngx_js.c
@@ -99,6 +99,16 @@ ngx_int_t
 ngx_js_call(njs_vm_t *vm, ngx_str_t *fname, ngx_log_t *log,
     njs_opaque_value_t *args, njs_uint_t nargs)
 {
+    njs_opaque_value_t  unused;
+
+    return ngx_js_invoke(vm, fname, log, args, nargs, &unused);
+}
+
+
+ngx_int_t
+ngx_js_invoke(njs_vm_t *vm, ngx_str_t *fname, ngx_log_t *log,
+    njs_opaque_value_t *args, njs_uint_t nargs, njs_opaque_value_t *retval)
+{
     njs_int_t        ret;
     njs_str_t        name;
     ngx_str_t        exception;
@@ -114,7 +124,8 @@ ngx_js_call(njs_vm_t *vm, ngx_str_t *fname, ngx_log_t *log,
         return NGX_ERROR;
     }
 
-    ret = njs_vm_call(vm, func, njs_value_arg(args), nargs);
+    ret = njs_vm_invoke(vm, func, njs_value_arg(args), nargs,
+                        njs_value_arg(retval));
     if (ret == NJS_ERROR) {
         ngx_js_retval(vm, NULL, &exception);
 
@@ -148,7 +159,7 @@ ngx_js_retval(njs_vm_t *vm, njs_opaque_value_t *retval, ngx_str_t *s)
         ret = njs_vm_value_string(vm, &str, njs_value_arg(retval));
 
     } else {
-        ret = njs_vm_retval_string(vm, &str);
+        ret = njs_vm_exception_string(vm, &str);
     }
 
     if (ret != NJS_OK) {
@@ -332,7 +343,7 @@ ngx_js_ext_conf_prefix(njs_vm_t *vm, njs_object_prop_t *prop,
 
 njs_int_t
 ngx_js_ext_log(njs_vm_t *vm, njs_value_t *args, njs_uint_t nargs,
-    njs_index_t level)
+    njs_index_t level, njs_value_t *retval)
 {
     char                *p;
     ngx_int_t            lvl;
@@ -370,7 +381,7 @@ ngx_js_ext_log(njs_vm_t *vm, njs_value_t *args, njs_uint_t nargs,
 
     c->log->handler = handler;
 
-    njs_value_undefined_set(njs_vm_retval(vm));
+    njs_value_undefined_set(retval);
 
     return NJS_OK;
 }
@@ -628,6 +639,7 @@ ngx_js_init_preload_vm(ngx_conf_t *cf, ngx_js_conf_t *conf)
     njs_int_t             ret;
     ngx_uint_t            i;
     njs_vm_opt_t          options;
+    njs_opaque_value_t    retval;
     ngx_js_named_path_t  *preload;
 
     njs_vm_opt_init(&options);
@@ -695,7 +707,7 @@ ngx_js_init_preload_vm(ngx_conf_t *cf, ngx_js_conf_t *conf)
         goto error;
     }
 
-    ret = njs_vm_start(vm);
+    ret = njs_vm_start(vm, njs_value_arg(&retval));
     if (ret != NJS_OK) {
         goto error;
     }
@@ -991,8 +1003,8 @@ ngx_js_init_conf_vm(ngx_conf_t *cf, ngx_js_conf_t *conf,
     rc = njs_vm_compile(conf->vm, &start, end);
 
     if (rc != NJS_OK) {
-        njs_value_assign(&exception, njs_vm_retval(conf->vm));
-        njs_vm_retval_string(conf->vm, &text);
+        njs_vm_exception_get(conf->vm, njs_value_arg(&exception));
+        njs_vm_value_string(conf->vm, &text, njs_value_arg(&exception));
 
         value = njs_vm_object_prop(conf->vm, njs_value_arg(&exception),
                                    &file_name_key, &lvalue);