Return unique_ptr from AstExpression::eval_* functions

...generally, idlc leaks most memory, and e.g. trying to turn
AstExpression::m_exprValue into a unique_ptr would fail because
AstExpression::eval_symbol returns a pointer to an object "owned" elsewhere (but
never actually deleted by its owner).  So improvement of idlc ends here---for
one, it does not improve anything to try and make idlc not leak memory, and for
another, idlc is doomed to go away anyway.

Change-Id: I36f54130c8bfd1933126ae7f8a982e50d9bc616e

idlc/inc/idlc/astexpression.hxx

@@ -19,6 +19,10 @@
 #ifndef INCLUDED_IDLC_INC_IDLC_ASTEXPRESSION_HXX
 #define INCLUDED_IDLC_INC_IDLC_ASTEXPRESSION_HXX
 
+#include <sal/config.h>
+
+#include <memory>
+
 #include <idlc/idlc.hxx>
 
 // Enum to define all the different operators to combine expressions
@@ -120,9 +124,9 @@ private:
     // Fill out the lineno, filename and definition scope details
     void    fillDefinitionDetails();
     // Evaluate different sets of operators
-    AstExprValue* eval_bin_op();
-    AstExprValue* eval_bit_op();
-    AstExprValue* eval_un_op();
+    std::unique_ptr<AstExprValue> eval_bin_op();
+    std::unique_ptr<AstExprValue> eval_bit_op();
+    std::unique_ptr<AstExprValue> eval_un_op();
     AstExprValue* eval_symbol();
 
     AstScope*       m_pScope;       // scope defined in

idlc/source/astexpression.cxx

@@ -885,19 +885,19 @@ void AstExpression::evaluate()
         case EC_mul:
         case EC_div:
         case EC_mod:
-            m_exprValue = eval_bin_op();
+            m_exprValue = eval_bin_op().release();
             break;
         case EC_or:
         case EC_xor:
         case EC_and:
         case EC_left:
         case EC_right:
-            m_exprValue = eval_bit_op();
+            m_exprValue = eval_bit_op().release();
             break;
         case EC_u_plus:
         case EC_u_minus:
         case EC_bit_neg:
-            m_exprValue = eval_un_op();
+            m_exprValue = eval_un_op().release();
             break;
         case EC_symbol:
             m_exprValue = eval_symbol();
@@ -907,7 +907,7 @@ void AstExpression::evaluate()
     }
 }
 
-AstExprValue* AstExpression::eval_bin_op()
+std::unique_ptr<AstExprValue> AstExpression::eval_bin_op()
 {
     ExprType eType = ET_double;
 
@@ -955,10 +955,10 @@ AstExprValue* AstExpression::eval_bin_op()
             return NULL;
     }
 
-    return retval.release();
+    return retval;
 }
 
-AstExprValue* AstExpression::eval_bit_op()
+std::unique_ptr<AstExprValue> AstExpression::eval_bit_op()
 {
     if (m_subExpr1 == NULL || m_subExpr2 == NULL)
         return NULL;
@@ -997,10 +997,10 @@ AstExprValue* AstExpression::eval_bit_op()
             return NULL;
     }
 
-    return retval.release();
+    return retval;
 }
 
-AstExprValue* AstExpression::eval_un_op()
+std::unique_ptr<AstExprValue> AstExpression::eval_un_op()
 {
     if (m_subExpr1 == NULL)
         return NULL;
@@ -1030,7 +1030,7 @@ AstExprValue* AstExpression::eval_un_op()
             return NULL;
     }
 
-    return retval.release();
+    return retval;
 }
 
 AstExprValue* AstExpression::eval_symbol()