Use new+delete for struct expression

In another series I'm working on, it is necessary to manage
"struct expression" with new and delete.  Because the patch is
straightforward and could be extracted, I've done so here.

gdb/ChangeLog
2020-12-01  Tom Tromey  <tom@tromey.com>

	* parse.c (expr_builder::expr_builder): Initialize expout.
	(expr_builder::release): Use expression::resize.
	(expression::expression, expression::~expression)
	(expression::resize): New methods.
	(write_exp_elt): Use expression::resize.
	(prefixify_expression): Update.
	(increase_expout_size): Use expression::resize.
	* expression.h (struct expression): Add constructor, destructor.
	<resize>: New method.
	(expression_up): Change type.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 39637aa92a59103269361e5a7032ad4e0da4f379..635435cbdeae41bcc0483797f01cf179eb193048 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,16 @@
+2020-12-01  Tom Tromey  <tom@tromey.com>
+
+       * parse.c (expr_builder::expr_builder): Initialize expout.
+       (expr_builder::release): Use expression::resize.
+       (expression::expression, expression::~expression)
+       (expression::resize): New methods.
+       (write_exp_elt): Use expression::resize.
+       (prefixify_expression): Update.
+       (increase_expout_size): Use expression::resize.
+       * expression.h (struct expression): Add constructor, destructor.
+       <resize>: New method.
+       (expression_up): Change type.
+
 2020-12-01  Rogerio A. Cardoso  <rcardoso@linux.ibm.com>
        * ppc-linux-nat.c: (PPC_DEBUG_FEATURE_DATA_BP_ARCH_31): New define.
        (region_ok_for_hw_watchpoint): Check if 2nd DAWR is avaliable before

diff --git a/gdb/expression.h b/gdb/expression.h
index a8bfac17d8b32d75210e0b1e206a12cfc4dafc41..684274b90b8ae42b0f94072ba6f424778d651f19 100644 (file)
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -93,15 +93,22 @@ union exp_element
   };
 
 struct expression
-  {
-    const struct language_defn *language_defn; /* language it was
-                                                  entered in.  */
-    struct gdbarch *gdbarch;  /* architecture it was parsed in.  */
-    int nelts;
-    union exp_element elts[1];
-  };
+{
+  expression (const struct language_defn *, struct gdbarch *, size_t);
+  ~expression ();
+  DISABLE_COPY_AND_ASSIGN (expression);
+
+  void resize (size_t);
+
+  /* Language it was entered in.  */
+  const struct language_defn *language_defn;
+  /* Architecture it was parsed in.  */
+  struct gdbarch *gdbarch;
+  int nelts = 0;
+  union exp_element *elts;
+};
 
-typedef gdb::unique_xmalloc_ptr<expression> expression_up;
+typedef std::unique_ptr<expression> expression_up;
 
 /* Macros for converting between number of expression elements and bytes
    to store that many expression elements.  */

diff --git a/gdb/parse.c b/gdb/parse.c
index c34b6085cd09eb9553a5b3855b8237686262a9d5..73d82e64a87a6a12d07a3df73ef3b1824cc452e0 100644 (file)
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -114,13 +114,9 @@ innermost_block_tracker::update (const struct block *b,
 expr_builder::expr_builder (const struct language_defn *lang,
                            struct gdbarch *gdbarch)
   : expout_size (10),
-    expout (XNEWVAR (expression,
-                    (sizeof (expression)
-                     + EXP_ELEM_TO_BYTES (expout_size)))),
+    expout (new expression (lang, gdbarch, expout_size)),
     expout_ptr (0)
 {
-  expout->language_defn = lang;
-  expout->gdbarch = gdbarch;
 }
 
 expression_up
@@ -131,13 +127,31 @@ expr_builder::release ()
      excess elements.  */
 
   expout->nelts = expout_ptr;
-  expout.reset (XRESIZEVAR (expression, expout.release (),
-                           (sizeof (expression)
-                            + EXP_ELEM_TO_BYTES (expout_ptr))));
+  expout->resize (expout_ptr);
 
   return std::move (expout);
 }
 
+expression::expression (const struct language_defn *lang, struct gdbarch *arch,
+                       size_t n)
+  : language_defn (lang),
+    gdbarch (arch),
+    elts (nullptr)
+{
+  resize (n);
+}
+
+expression::~expression ()
+{
+  xfree (elts);
+}
+
+void
+expression::resize (size_t n)
+{
+  elts = XRESIZEVAR (union exp_element, elts, EXP_ELEM_TO_BYTES (n));
+}
+
 /* This page contains the functions for adding data to the struct expression
    being constructed.  */
 
@@ -152,9 +166,7 @@ write_exp_elt (struct expr_builder *ps, const union exp_element *expelt)
   if (ps->expout_ptr >= ps->expout_size)
     {
       ps->expout_size *= 2;
-      ps->expout.reset (XRESIZEVAR (expression, ps->expout.release (),
-                                   (sizeof (expression)
-                                    + EXP_ELEM_TO_BYTES (ps->expout_size))));
+      ps->expout->resize (ps->expout_size);
     }
   ps->expout->elts[ps->expout_ptr++] = *expelt;
 }
@@ -721,16 +733,14 @@ int
 prefixify_expression (struct expression *expr, int last_struct)
 {
   gdb_assert (expr->nelts > 0);
-  int len = sizeof (struct expression) + EXP_ELEM_TO_BYTES (expr->nelts);
-  struct expression *temp;
+  int len = EXP_ELEM_TO_BYTES (expr->nelts);
+  struct expression temp (expr->language_defn, expr->gdbarch, expr->nelts);
   int inpos = expr->nelts, outpos = 0;
 
-  temp = (struct expression *) alloca (len);
-
   /* Copy the original expression into temp.  */
-  memcpy (temp, expr, len);
+  memcpy (temp.elts, expr->elts, len);
 
-  return prefixify_subexp (temp, expr, inpos, outpos, last_struct);
+  return prefixify_subexp (&temp, expr, inpos, outpos, last_struct);
 }
 
 /* Return the number of exp_elements in the postfix subexpression 
@@ -1412,10 +1422,7 @@ increase_expout_size (struct expr_builder *ps, size_t lenelt)
     {
       ps->expout_size = std::max (ps->expout_size * 2,
                                  ps->expout_ptr + lenelt + 10);
-      ps->expout.reset (XRESIZEVAR (expression,
-                                   ps->expout.release (),
-                                   (sizeof (struct expression)
-                                    + EXP_ELEM_TO_BYTES (ps->expout_size))));
+      ps->expout->resize (ps->expout_size);
     }
 }