Make dwarf_expr_context::stack an std::vector

Replace the manually managed array with a vector.  It is mostly
straightforward, except maybe one thing in execute_stack_op, in the
handling of DW_OP_fbreg.  When the code stumbles on that opcode while
evaluating an expression, it needs to evaluate a subexpression to find
where the fb reg has been saved.  Rather than creating a new context, it
reuses the current context.  It saves the size of the stack before and
restores the stack to that size after.

I think we can do a little bit better by saving the current stack
locally and installing a new empty stack.  This way, if the
subexpression is malformed and underflows, we'll get an exception.
Before, it would have overwritten the top elements of the top-level
expression.  The evaluation of the top-level expression would have then
resumed with the same stack size, but possibly some corrupted elements.

gdb/ChangeLog:

	* dwarf2expr.h (dwarf_stack_value): Add constructor.
	(dwarf_expr_context) <~dwarf_expr_context>: Define as default.
	<stack>: Change type to std::vector.
	<stack_len, stack_allocated>: Remove.
	<grow_stack>: Remove.
	* dwarf2expr.c (dwarf_expr_context::dwarf_expr_context): Adjust.
	(dwarf_expr_context::~dwarf_expr_context): Remove.
	(dwarf_expr_context::grow_stack): Remove.
	(dwarf_expr_context::push): Adjust.
	(dwarf_expr_context::pop): Adjust.
	(dwarf_expr_context::fetch): Adjust.
	(dwarf_expr_context::fetch_in_stack_memory): Adjust.
	(dwarf_expr_context::stack_empty_p): Adjust.
	(dwarf_expr_context::execute_stack_op): Adjust.

1 files changed, 7 insertions, 8 deletions

diff --git a/gdb/dwarf2expr.h b/gdb/dwarf2expr.h
index 0a57bee..a8d6ae1 100644
--- a/gdb/dwarf2expr.h
+++ b/gdb/dwarf2expr.h
@@ -100,6 +100,10 @@ struct dwarf_expr_piece
 
 struct dwarf_stack_value
 {
+  dwarf_stack_value (struct value *value_, int in_stack_memory_)
+  : value (value_), in_stack_memory (in_stack_memory_)
+  {}
+
   struct value *value;
 
   /* True if the piece is in memory and is known to be on the program's stack.
@@ -114,7 +118,7 @@ struct dwarf_stack_value
 struct dwarf_expr_context
 {
   dwarf_expr_context ();
-  virtual ~dwarf_expr_context ();
+  virtual ~dwarf_expr_context () = default;
 
   void push_address (CORE_ADDR value, bool in_stack_memory);
   void eval (const gdb_byte *addr, size_t len);
@@ -122,12 +126,8 @@ struct dwarf_expr_context
   CORE_ADDR fetch_address (int n);
   bool fetch_in_stack_memory (int n);
 
-  /* The stack of values, allocated with xmalloc.  */
-  struct dwarf_stack_value *stack;
-
-  /* The number of values currently pushed on the stack, and the
-     number of elements allocated to the stack.  */
-  int stack_len, stack_allocated;
+  /* The stack of values.  */
+  std::vector<dwarf_stack_value> stack;
 
   /* Target architecture to use for address operations.  */
   struct gdbarch *gdbarch;
@@ -249,7 +249,6 @@ struct dwarf_expr_context
 private:
 
   struct type *address_type () const;
-  void grow_stack (size_t need);
   void push (struct value *value, bool in_stack_memory);
   bool stack_empty_p () const;
   void add_piece (ULONGEST size, ULONGEST offset);