Re: [4/5] implement "info vtable"

[Tom Tromey <tromey at redhat dot com>]

Pedro> My only gripe is that we end up with the vtable vs vtbl inconsistency

In the end I chose to rename the new command to 'info vtbl', mostly out
of inertia.

Pedro> IIUC, "info vtable POINTER" works.  The tests only sees to try
Pedro> "info vtable OBJ".  Worth adding a test that tries through a pointer?

I did this.

Pedro> Thanks.  While at it, it might be worth it to add a test that
Pedro> tries "info vtable" (no arg), "info vtable foo" with a foo object
Pedro> that doesn't have a vtable, and perhaps also "info vtable
Pedro> some_scalar".

This too.

Here's what I am checking in.

Tom

2012-03-15  Tom Tromey  <tromey@redhat.com>

	* gnu-v3-abi.c (struct value_and_voffset): New.
	(hash_value_and_voffset, eq_value_and_voffset)
	(compare_value_and_voffset, compute_vtable_size)
	(print_one_vtable, gnuv3_print_vtable): New functions.
	(init_gnuv3_ops): Initialize 'print_vtable' field.
	* cp-support.c (info_vtbl_command): New function.
	(_initialize_cp_support): Add "info vtbl".
	* cp-abi.h (cplus_print_vtable): Declare.
	(struct cp_abi_ops) <print_vtable>: New field.
	* cp-abi.c (cplus_print_vtable): New function.
	* NEWS: Update.

2012-03-15  Tom Tromey  <tromey@redhat.com>

	* gdb.texinfo (Debugging C Plus Plus): Document "info vtbl".

2012-03-15  Tom Tromey  <tromey@redhat.com>

	* gdb.cp/virtfunc.exp (make_one_vtable_result): New proc.
	(test_info_vtbl): Likewise.
	(do_tests): Call test_info_vtbl.
	* gdb.cp/virtfunc.cc (va): New global.

Index: NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.497
diff -u -r1.497 NEWS
--- NEWS	13 Mar 2012 21:02:36 -0000	1.497
+++ NEWS	15 Mar 2012 15:41:16 -0000
@@ -70,6 +70,9 @@
   ** "enable count" can be used to auto-disable a breakpoint after
      several hits.
 
+  ** "info vtable" can be used to show the virtual method tables for
+     C++ and Java objects.
+
 * New targets
 
 Renesas RL78			rl78-*-elf
Index: cp-abi.c
===================================================================
RCS file: /cvs/src/src/gdb/cp-abi.c,v
retrieving revision 1.34
diff -u -r1.34 cp-abi.c
--- cp-abi.c	6 Jan 2012 03:34:46 -0000	1.34
+++ cp-abi.c	15 Mar 2012 15:41:16 -0000
@@ -169,6 +169,16 @@
   return (*current_cp_abi.method_ptr_to_value) (this_p, method_ptr);
 }
 
+/* See cp-abi.h.  */
+
+void
+cplus_print_vtable (struct value *value)
+{
+  if (current_cp_abi.print_vtable == NULL)
+    error (_("GDB cannot print the vtable on this target"));
+  return (*current_cp_abi.print_vtable) (value);
+}
+
 int
 cp_pass_by_reference (struct type *type)
 {
Index: cp-abi.h
===================================================================
RCS file: /cvs/src/src/gdb/cp-abi.h,v
retrieving revision 1.23
diff -u -r1.23 cp-abi.h
--- cp-abi.h	4 Jan 2012 08:17:00 -0000	1.23
+++ cp-abi.h	15 Mar 2012 15:41:16 -0000
@@ -173,6 +173,11 @@
 void cplus_make_method_ptr (struct type *type, gdb_byte *CONTENTS,
 			    CORE_ADDR address, int is_virtual);
 
+/* Print the vtable for VALUE, if there is one.  If there is no
+   vtable, print a message, but do not throw.  */
+
+void cplus_print_vtable (struct value *value);
+
 /* Determine if we are currently in a C++ thunk.  If so, get the
    address of the routine we are thunking to and continue to there
    instead.  */
@@ -213,6 +218,7 @@
 			   CORE_ADDR, int);
   struct value * (*method_ptr_to_value) (struct value **,
 					 struct value *);
+  void (*print_vtable) (struct value *);
   CORE_ADDR (*skip_trampoline) (struct frame_info *, CORE_ADDR);
   int (*pass_by_reference) (struct type *type);
 };
Index: cp-support.c
===================================================================
RCS file: /cvs/src/src/gdb/cp-support.c,v
retrieving revision 1.54
diff -u -r1.54 cp-support.c
--- cp-support.c	7 Feb 2012 04:48:18 -0000	1.54
+++ cp-support.c	15 Mar 2012 15:41:16 -0000
@@ -34,6 +34,7 @@
 #include "exceptions.h"
 #include "expression.h"
 #include "value.h"
+#include "cp-abi.h"
 
 #include "safe-ctype.h"
 
@@ -1563,6 +1564,17 @@
   return 0;
 }
 
+/* Implement "info vtable".  */
+
+static void
+info_vtbl_command (char *arg, int from_tty)
+{
+  struct value *value;
+
+  value = parse_and_eval (arg);
+  cplus_print_vtable (value);
+}
+
 void
 _initialize_cp_support (void)
 {
@@ -1581,4 +1593,10 @@
 	   first_component_command,
 	   _("Print the first class/namespace component of NAME."),
 	   &maint_cplus_cmd_list);
+
+  add_info ("vtbl", info_vtbl_command,
+	    _("Show the vtable for a C++ object.\n\
+Usage: info vtbl EXPRESSION\n\
+Evaluate EXPRESSION and display the virtual function table for the\n\
+resulting object."));
 }
Index: gnu-v3-abi.c
===================================================================
RCS file: /cvs/src/src/gdb/gnu-v3-abi.c,v
retrieving revision 1.69
diff -u -r1.69 gnu-v3-abi.c
--- gnu-v3-abi.c	7 Feb 2012 04:48:21 -0000	1.69
+++ gnu-v3-abi.c	15 Mar 2012 15:41:16 -0000
@@ -26,6 +26,7 @@
 #include "objfiles.h"
 #include "valprint.h"
 #include "c-lang.h"
+#include "exceptions.h"
 
 #include "gdb_assert.h"
 #include "gdb_string.h"
@@ -725,6 +726,245 @@
     return value_from_pointer (lookup_pointer_type (method_type), ptr_value);
 }
 
+/* Objects of this type are stored in a hash table and a vector when
+   printing the vtables for a class.  */
+
+struct value_and_voffset
+{
+  /* The value representing the object.  */
+  struct value *value;
+
+  /* The maximum vtable offset we've found for any object at this
+     offset in the outermost object.  */
+  int max_voffset;
+};
+
+typedef struct value_and_voffset *value_and_voffset_p;
+DEF_VEC_P (value_and_voffset_p);
+
+/* Hash function for value_and_voffset.  */
+
+static hashval_t
+hash_value_and_voffset (const void *p)
+{
+  const struct value_and_voffset *o = p;
+
+  return value_address (o->value) + value_embedded_offset (o->value);
+}
+
+/* Equality function for value_and_voffset.  */
+
+static int
+eq_value_and_voffset (const void *a, const void *b)
+{
+  const struct value_and_voffset *ova = a;
+  const struct value_and_voffset *ovb = b;
+
+  return (value_address (ova->value) + value_embedded_offset (ova->value)
+	  == value_address (ovb->value) + value_embedded_offset (ovb->value));
+}
+
+/* qsort comparison function for value_and_voffset.  */
+
+static int
+compare_value_and_voffset (const void *a, const void *b)
+{
+  const struct value_and_voffset * const *ova = a;
+  CORE_ADDR addra = (value_address ((*ova)->value)
+		     + value_embedded_offset ((*ova)->value));
+  const struct value_and_voffset * const *ovb = b;
+  CORE_ADDR addrb = (value_address ((*ovb)->value)
+		     + value_embedded_offset ((*ovb)->value));
+
+  if (addra < addrb)
+    return -1;
+  if (addra > addrb)
+    return 1;
+  return 0;
+}
+
+/* A helper function used when printing vtables.  This determines the
+   key (most derived) sub-object at each address and also computes the
+   maximum vtable offset seen for the corresponding vtable.  Updates
+   OFFSET_HASH and OFFSET_VEC with a new value_and_voffset object, if
+   needed.  VALUE is the object to examine.  */
+
+static void
+compute_vtable_size (htab_t offset_hash,
+		     VEC (value_and_voffset_p) **offset_vec,
+		     struct value *value)
+{
+  int i;
+  struct type *type = check_typedef (value_type (value));
+  void **slot;
+  struct value_and_voffset search_vo, *current_vo;
+  CORE_ADDR addr = value_address (value) + value_embedded_offset (value);
+
+  /* If the object is not dynamic, then we are done; as it cannot have
+     dynamic base types either.  */
+  if (!gnuv3_dynamic_class (type))
+    return;
+
+  /* Update the hash and the vec, if needed.  */
+  search_vo.value = value;
+  slot = htab_find_slot (offset_hash, &search_vo, INSERT);
+  if (*slot)
+    current_vo = *slot;
+  else
+    {
+      current_vo = XNEW (struct value_and_voffset);
+      current_vo->value = value;
+      current_vo->max_voffset = -1;
+      *slot = current_vo;
+      VEC_safe_push (value_and_voffset_p, *offset_vec, current_vo);
+    }
+
+  /* Update the value_and_voffset object with the highest vtable
+     offset from this class.  */
+  for (i = 0; i < TYPE_NFN_FIELDS (type); ++i)
+    {
+      int j;
+      struct fn_field *fn = TYPE_FN_FIELDLIST1 (type, i);
+
+      for (j = 0; j < TYPE_FN_FIELDLIST_LENGTH (type, i); ++j)
+	{
+	  if (TYPE_FN_FIELD_VIRTUAL_P (fn, j))
+	    {
+	      int voffset = TYPE_FN_FIELD_VOFFSET (fn, j);
+
+	      if (voffset > current_vo->max_voffset)
+		current_vo->max_voffset = voffset;
+	    }
+	}
+    }
+
+  /* Recurse into base classes.  */
+  for (i = 0; i < TYPE_N_BASECLASSES (type); ++i)
+    compute_vtable_size (offset_hash, offset_vec, value_field (value, i));
+}
+
+/* Helper for gnuv3_print_vtable that prints a single vtable.  */
+
+static void
+print_one_vtable (struct gdbarch *gdbarch, struct value *value,
+		  int max_voffset,
+		  struct value_print_options *opts)
+{
+  int i;
+  struct type *type = check_typedef (value_type (value));
+  struct value *vtable;
+  CORE_ADDR vt_addr;
+
+  vtable = gnuv3_get_vtable (gdbarch, type,
+			     value_address (value)
+			     + value_embedded_offset (value));
+  vt_addr = value_address (value_field (vtable,
+					vtable_field_virtual_functions));
+
+  printf_filtered (_("vtable for '%s' @ %s (subobject @ %s):\n"),
+		   TYPE_SAFE_NAME (type),
+		   paddress (gdbarch, vt_addr),
+		   paddress (gdbarch, (value_address (value)
+				       + value_embedded_offset (value))));
+
+  for (i = 0; i <= max_voffset; ++i)
+    {
+      struct value *vfn;
+      CORE_ADDR addr;
+      volatile struct gdb_exception ex;
+
+      printf_filtered ("[%d]: ", i);
+
+      vfn = value_subscript (value_field (vtable,
+					  vtable_field_virtual_functions),
+			     i);
+
+      if (gdbarch_vtable_function_descriptors (gdbarch))
+	vfn = value_addr (vfn);
+
+      TRY_CATCH (ex, RETURN_MASK_ERROR)
+	{
+	  addr = value_as_address (vfn);
+	}
+      if (ex.reason < 0)
+	printf_filtered (_("<error: %s>"), ex.message);
+      else
+	print_function_pointer_address (gdbarch, addr, gdb_stdout,
+					opts->addressprint);
+      printf_filtered ("\n");
+    }
+}
+
+/* Implementation of the print_vtable method.  */
+
+static void
+gnuv3_print_vtable (struct value *value)
+{
+  struct gdbarch *gdbarch;
+  struct type *type;
+  struct value *vtable;
+  struct value_print_options opts;
+  htab_t offset_hash;
+  struct cleanup *cleanup;
+  VEC (value_and_voffset_p) *result_vec;
+  struct value_and_voffset *iter;
+  int i, count;
+
+  value = coerce_ref (value);
+  type = check_typedef (value_type (value));
+  if (TYPE_CODE (type) == TYPE_CODE_PTR)
+    {
+      value = value_ind (value);
+      type = check_typedef (value_type (value));
+    }
+
+  get_user_print_options (&opts);
+
+  /* Respect 'set print object'.  */
+  if (opts.objectprint)
+    {
+      value = value_full_object (value, NULL, 0, 0, 0);
+      type = check_typedef (value_type (value));
+    }
+
+  gdbarch = get_type_arch (type);
+  vtable = gnuv3_get_vtable (gdbarch, type,
+			     value_as_address (value_addr (value)));
+
+  if (!vtable)
+    {
+      printf_filtered (_("This object does not have a virtual function table\n"));
+      return;
+    }
+
+  offset_hash = htab_create_alloc (1, hash_value_and_voffset,
+				   eq_value_and_voffset,
+				   xfree, xcalloc, xfree);
+  cleanup = make_cleanup_htab_delete (offset_hash);
+  make_cleanup (VEC_cleanup (value_and_voffset_p), &result_vec);
+
+  compute_vtable_size (offset_hash, &result_vec, value);
+
+  qsort (VEC_address (value_and_voffset_p, result_vec),
+	 VEC_length (value_and_voffset_p, result_vec),
+	 sizeof (value_and_voffset_p),
+	 compare_value_and_voffset);
+
+  count = 0;
+  for (i = 0; VEC_iterate (value_and_voffset_p, result_vec, i, iter); ++i)
+    {
+      if (iter->max_voffset >= 0)
+	{
+	  if (count > 0)
+	    printf_filtered ("\n");
+	  print_one_vtable (gdbarch, iter->value, iter->max_voffset, &opts);
+	  ++count;
+	}
+    }
+
+  do_cleanups (cleanup);
+}
+
 /* Determine if we are currently in a C++ thunk.  If so, get the address
    of the routine we are thunking to and continue to there instead.  */
 
@@ -873,6 +1113,7 @@
   gnu_v3_abi_ops.method_ptr_size = gnuv3_method_ptr_size;
   gnu_v3_abi_ops.make_method_ptr = gnuv3_make_method_ptr;
   gnu_v3_abi_ops.method_ptr_to_value = gnuv3_method_ptr_to_value;
+  gnu_v3_abi_ops.print_vtable = gnuv3_print_vtable;
   gnu_v3_abi_ops.skip_trampoline = gnuv3_skip_trampoline;
   gnu_v3_abi_ops.pass_by_reference = gnuv3_pass_by_reference;
 }
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.932
diff -u -r1.932 gdb.texinfo
--- doc/gdb.texinfo	13 Mar 2012 21:02:36 -0000	1.932
+++ doc/gdb.texinfo	15 Mar 2012 15:41:21 -0000
@@ -12788,6 +12788,12 @@
 @var{typename}.
 @xref{Symbols, ,Examining the Symbol Table}.
 
+@item info vtbl @var{expression}.
+The @code{info vtbl} command can be used to display the virtual
+method tables of the object computed by @var{expression}.  This shows
+one entry per virtual table; there may be multiple virtual tables when
+multiple inheritance is in use.
+
 @cindex C@t{++} symbol display
 @item set print demangle
 @itemx show print demangle
Index: testsuite/gdb.cp/virtfunc.cc
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/virtfunc.cc,v
retrieving revision 1.6
diff -u -r1.6 virtfunc.cc
--- testsuite/gdb.cp/virtfunc.cc	4 Jan 2012 08:17:47 -0000	1.6
+++ testsuite/gdb.cp/virtfunc.cc	15 Mar 2012 15:41:24 -0000
@@ -111,6 +111,7 @@
 E   e;
 V   v;
 VB  vb;
+VA  va;
 
 
 A* 	pAa	= 	&a;
Index: testsuite/gdb.cp/virtfunc.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/virtfunc.exp,v
retrieving revision 1.25
diff -u -r1.25 virtfunc.exp
--- testsuite/gdb.cp/virtfunc.exp	16 Jan 2012 16:21:45 -0000	1.25
+++ testsuite/gdb.cp/virtfunc.exp	15 Mar 2012 15:41:24 -0000
@@ -226,6 +226,54 @@
     }
 }
 
+# A helper proc that creates a regular expression matching a
+# particular vtable.  NAME is the type name.  Each element of ARGS is
+# the name of a function in the vtable.
+
+proc make_one_vtable_result {name args} {
+    global hex
+
+    set nls "\[\r\n\]+"
+
+    set result "vtable for '${name}' @ $hex .subobject @ $hex.:$nls"
+    set count 0
+    foreach func $args {
+	append result ".${count}.: $hex <$func..>${nls}"
+	incr count
+    }
+
+    return $result
+}
+
+# Test "info vtbl".
+
+proc test_info_vtbl {} {
+    global hex
+
+    set nls "\[\r\n\]+"
+
+    set vt_A [make_one_vtable_result A A::f]
+    set vt_B [make_one_vtable_result B B::f]
+    set vt_V [make_one_vtable_result V VB::vvb V::vv]
+    set vt_V2 [make_one_vtable_result V VB::vvb "virtual thunk to E::vv"]
+    set vt_D [make_one_vtable_result D D::vg D::vd]
+    set vt_D2 [make_one_vtable_result D "non-virtual thunk to E::vg" D::vd]
+    set vt_E [make_one_vtable_result E E::f E::vg E::vv]
+
+    gdb_test "info vtbl a" "${vt_A}${vt_V}"
+    gdb_test "info vtbl b" "${vt_B}${vt_V}"
+    gdb_test "info vtbl c" "${vt_V}"
+    gdb_test "info vtbl d" "${vt_D}${vt_V}"
+    gdb_test "info vtbl e" "${vt_E}${vt_D2}${vt_V2}"
+    gdb_test "info vtbl pEe" "${vt_E}${vt_D2}${vt_V2}"
+
+    gdb_test "info vtbl" "Argument required.*"
+    gdb_test "info vtbl va" \
+	"This object does not have a virtual function table.*"
+    gdb_test "info vtbl all_count" \
+	"This object does not have a virtual function table.*"
+}
+
 proc do_tests {} {
     global srcdir subdir binfile
     global gdb_prompt
@@ -244,6 +292,7 @@
 	return
     }
     test_ptype_of_classes
+    test_info_vtbl
 
     gdb_breakpoint test_calls
     gdb_test "continue" ".*Breakpoint .* test_calls.*" ""