jerry_init: Calculate structure part address more safely. (#3545)

GCC 9.2 issues a warning-as-error trying to perform a large memset into
what it thinks as a single field of a structure. So, instead of taking
an address of that field, perform explicit address calculaton using
structure address and offset of that field.

Fixes #3544.

JerryScript-DCO-1.0-Signed-off-by: Paul Sokolovsky paul.sokolovsky@linaro.org

Author: pfalcon

jerry-core/api/jerry.c

@@ -191,7 +191,7 @@ jerry_init (jerry_init_flag_t flags) /**< combination of Jerry flags */
   JERRY_ASSERT (!(JERRY_CONTEXT (status_flags) & ECMA_STATUS_API_AVAILABLE));
 
   /* Zero out all non-external members. */
-  memset (&JERRY_CONTEXT (JERRY_CONTEXT_FIRST_MEMBER), 0,
+  memset ((char *) &JERRY_CONTEXT_STRUCT + offsetof (jerry_context_t, JERRY_CONTEXT_FIRST_MEMBER), 0,
           sizeof (jerry_context_t) - offsetof (jerry_context_t, JERRY_CONTEXT_FIRST_MEMBER));
 
   JERRY_CONTEXT (jerry_init_flags) = flags;

jerry-core/jcontext/jcontext.h

@@ -245,6 +245,7 @@ struct jerry_context_t
  * This part is for JerryScript which uses external context.
  */
 
+#define JERRY_CONTEXT_STRUCT (*jerry_port_get_current_context ())
 #define JERRY_CONTEXT(field) (jerry_port_get_current_context ()->field)
 
 #if !ENABLED (JERRY_SYSTEM_ALLOCATOR)
@@ -274,6 +275,11 @@ struct jmem_heap_t
  */
 extern jerry_context_t jerry_global_context;
 
+/**
+ * Config-independent name for context.
+ */
+#define JERRY_CONTEXT_STRUCT (jerry_global_context)
+
 /**
  * Provides a reference to a field in the current context.
  */