Fixed #74: disable reading/writing partial volatile variables through…

… pointers

src/Variable.cpp

@@ -570,6 +570,29 @@ Variable::is_const_after_deref(int deref_level) const
 	return false;
 }
 
+bool
+Variable::is_partial_volatile_after_deref(int deref_level) const
+{
+	if (deref_level < 0) {
+		return false;
+	}
+	// check if the whole struct/union type is volatile
+	if (qfer.is_volatile_after_deref(deref_level)) {
+		return false;
+	}
+	if (type) {
+		// check individual fields
+		int i;
+		const Type* t = type;
+		for (i = 0; i < deref_level; i++) {
+			t = t->ptr_type;
+		}
+		assert(t);
+		return t->is_volatile_struct_union();
+	}
+	return false;
+}
+
 bool
 Variable::is_volatile_after_deref(int deref_level) const
 {

src/Variable.h

@@ -86,6 +86,7 @@ class Variable
 	bool is_volatile(void) const;
 	bool is_access_once(void) const { return isAccessOnce; }
 	bool is_const_after_deref(int deref_level) const;
+	bool is_partial_volatile_after_deref(int deref_level) const;
 	bool is_volatile_after_deref(int deref_level) const;
 	bool is_packed_aggregate_field_var() const;
 	bool has_field_var(const Variable* v) const;

src/VariableSelector.cpp

@@ -244,6 +244,14 @@ VariableSelector::is_eligible_var(const Variable* var, int deref_level, Effect::
 		}
 		var = coll;
 	}
+
+	// Partial volatile variables are struct/union containing a
+	// volatile field. Reading/writing them through pointers is
+	// problematic. See issue #74 for details.
+	if (deref_level > 0 && var->is_partial_volatile_after_deref(deref_level)) {
+		return false;
+	}
+
 	const Effect &effect_context = cg_context.get_effect_context();
 	bool is_const = var->is_const_after_deref(deref_level);
 	bool is_volatile = var->is_volatile_after_deref(deref_level) || var->is_volatile();