[PATCH 22/43] Add to_value method to DWARF entry classes

[Zoran Zaric via Gdb-patches <gdb-patches@sourceware.org>]

Following the idea from the last patch this patch is adding another
conversion method from any DWARF entry object into a DWARF value
object.

Currently, we only know how to convert from a memory location
description into a value, but it is resonable to expect a set of target
hooks that would let the target decide on how to do other conversions
in the future.

gdb/ChangeLog:

        * dwarf2/expr.c (dwarf_entry::to_value): New method.
        (dwarf_location::to_value): New method.
        (dwarf_memory::to_value): New method.
        (ill_formed_expression): New function.
---
 gdb/dwarf2/expr.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/gdb/dwarf2/expr.c b/gdb/dwarf2/expr.c
index d0c0efd2d31..69be36fcf2d 100644
--- a/gdb/dwarf2/expr.c
+++ b/gdb/dwarf2/expr.c
@@ -97,6 +97,14 @@ bits_to_bytes (ULONGEST start, ULONGEST n_bits)
   return (start % HOST_CHAR_BIT + n_bits + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 }
 
+/* Throw an exception about the invalid DWARF expression.  */
+
+static void
+ill_formed_expression ()
+{
+  error (_("Ill-formed DWARF expression"));
+}
+
 /* See expr.h.  */
 
 CORE_ADDR
@@ -279,6 +287,7 @@ write_to_memory (CORE_ADDR address, const gdb_byte *buffer,
 
 class dwarf_location;
 class dwarf_memory;
+class dwarf_value;
 
 /* Base class that describes entries found on a DWARF expression
    evaluation stack.  */
@@ -295,6 +304,11 @@ class dwarf_entry : public std::enable_shared_from_this<dwarf_entry>
      defines an architecture of the location described.   */
   virtual std::shared_ptr<dwarf_location> to_location
     (struct gdbarch *arch) = 0;
+
+  /* Convert DWARF entry into a DWARF value.  TYPE defines a
+     desired type of the returned DWARF value if it already
+     doesnt have one.  */
+  virtual std::shared_ptr<dwarf_value> to_value (struct type *type) = 0;
 };
 
 dwarf_entry::~dwarf_entry () = default;
@@ -345,6 +359,16 @@ class dwarf_location : public dwarf_entry
     return std::dynamic_pointer_cast<dwarf_location> (shared_from_this ());
   }
 
+  /* Convert DWARF entry into a DWARF value.  If the conversion
+     from that location description kind to a value is not supported
+     the result is an empty pointer.  TYPE defines a desired type of
+     the returned DWARF value if it already doesnt have one.  */
+  virtual std::shared_ptr<dwarf_value> to_value (struct type *type) override
+  {
+    ill_formed_expression ();
+    return std::shared_ptr<dwarf_value> (nullptr);
+  }
+
 protected:
   /* Architecture of the location.  */
   struct gdbarch *m_arch;
@@ -409,6 +433,14 @@ class dwarf_value : public dwarf_entry
      ARCH defines an architecture of the location described.  */
   std::shared_ptr<dwarf_location> to_location (struct gdbarch *arch) override;
 
+  /* Convert DWARF entry into a DWARF value.  If the entry
+     is already a value, it is just returned and the TYPE type
+     information is ignored.  */
+  std::shared_ptr<dwarf_value> to_value (struct type *type) override
+  {
+    return std::dynamic_pointer_cast<dwarf_value> (shared_from_this ());
+  }
+
 private:
   /* Value contents as a stream of bytes in target byte order.  */
   gdb::unique_xmalloc_ptr<gdb_byte> m_contents;
@@ -459,11 +491,19 @@ class dwarf_memory : public dwarf_location
     m_stack = stack;
   };
 
+  std::shared_ptr<dwarf_value> to_value (struct type *type) override;
+
 private:
   /* True if the location belongs to a stack memory region.  */
   bool m_stack;
 };
 
+std::shared_ptr<dwarf_value>
+dwarf_memory::to_value (struct type *type)
+{
+  return std::make_shared<dwarf_value> (m_offset, type);
+}
+
 /* Register location description entry.  */
 
 class dwarf_register : public dwarf_location
-- 
2.17.1