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authorMartin Galvan <martin.galvan@tallertechnologies.com>2016-05-31 15:54:01 -0300
committerMartin Galvan <martin.galvan@tallertechnologies.com>2016-05-31 15:56:34 -0300
commit3326303bf5ae4c92f2fbbff387ce231a16c1c8bf (patch)
tree6003faaf0747941817afc8d62f9f2a0bffcd3802 /gdb/dwarf2loc.c
parentf7433f011ef27838551aded73b8666a86d26b8ec (diff)
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[PR gdb/19893] Fix handling of synthetic C++ references
https://sourceware.org/bugzilla/show_bug.cgi?id=19893 I've traced the main source of the problem to pieced_value_funcs.coerce_ref not being implemented. Since gdb always assumes references are implemented as pointers, this causes it to think that it's dealing with a NULL pointer, thus breaking any operations involving synthetic references. What I did here was implementing pieced_value_funcs.coerce_ref using some of the synthetic pointer handling code from indirect_pieced_value, as Pedro suggested. I also made a few adjustments to the reference printing code so that it correctly shows either the address of the referenced value or (if it's non-addressable) the "<synthetic pointer>" string. I also wrote some unit tests based on Dwarf::assemble; these took a while to make because in most cases I needed a synthetic reference to a physical variable. Additionally, I started working on a unit test for classes that have a vtable, but ran into a few issues so that'll probably go in a future patch. One thing that should definitely be fixed is that proc function_range (called for MACRO_AT_func) will always try to compile/link using gcc with the default options instead of g++, thus breaking C++ compilations that require e.g. libstdc++. gdb/ChangeLog: * dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer, fetch_const_value_from_synthetic_pointer): New functions. (indirect_pieced_value): Move lower half to indirect_synthetic_pointer. (pieced_value_funcs): Implement coerce_ref. * valops.c (value_addr): Call coerce_ref for synthetic references. * valprint.c (valprint_check_validity): Return true for synthetic references. Also, don't show "<synthetic pointer>" if they reference addressable values. (generic_val_print_ref): Handle synthetic references. Also move some code to print_ref_address. (print_ref_address, get_value_addr_contents): New functions. gdb/testsuite/ChangeLog: * gdb.dwarf2/implref.exp: Rename to... * gdb.dwarf2/implref-const.exp: ...this. Also add more test statements. * gdb.dwarf2/implref-array.c: New file. * gdb.dwarf2/implref-array.exp: Likewise. * gdb.dwarf2/implref-global.c: Likewise. * gdb.dwarf2/implref-global.exp: Likewise. * gdb.dwarf2/implref-struct.c: Likewise. * gdb.dwarf2/implref-struct.exp: Likewise.
Diffstat (limited to 'gdb/dwarf2loc.c')
-rw-r--r--gdb/dwarf2loc.c128
1 files changed, 93 insertions, 35 deletions
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index bfe1173..adb0ac2 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -2061,6 +2061,66 @@ get_frame_address_in_block_wrapper (void *baton)
return get_frame_address_in_block ((struct frame_info *) baton);
}
+/* Fetch a DW_AT_const_value through a synthetic pointer. */
+
+static struct value *
+fetch_const_value_from_synthetic_pointer (sect_offset die, LONGEST byte_offset,
+ struct dwarf2_per_cu_data *per_cu,
+ struct type *type)
+{
+ struct value *result = NULL;
+ struct obstack temp_obstack;
+ struct cleanup *cleanup;
+ const gdb_byte *bytes;
+ LONGEST len;
+
+ obstack_init (&temp_obstack);
+ cleanup = make_cleanup_obstack_free (&temp_obstack);
+ bytes = dwarf2_fetch_constant_bytes (die, per_cu, &temp_obstack, &len);
+
+ if (bytes != NULL)
+ {
+ if (byte_offset >= 0
+ && byte_offset + TYPE_LENGTH (TYPE_TARGET_TYPE (type)) <= len)
+ {
+ bytes += byte_offset;
+ result = value_from_contents (TYPE_TARGET_TYPE (type), bytes);
+ }
+ else
+ invalid_synthetic_pointer ();
+ }
+ else
+ result = allocate_optimized_out_value (TYPE_TARGET_TYPE (type));
+
+ do_cleanups (cleanup);
+
+ return result;
+}
+
+/* Fetch the value pointed to by a synthetic pointer. */
+
+static struct value *
+indirect_synthetic_pointer (sect_offset die, LONGEST byte_offset,
+ struct dwarf2_per_cu_data *per_cu,
+ struct frame_info *frame, struct type *type)
+{
+ /* Fetch the location expression of the DIE we're pointing to. */
+ struct dwarf2_locexpr_baton baton
+ = dwarf2_fetch_die_loc_sect_off (die, per_cu,
+ get_frame_address_in_block_wrapper, frame);
+
+ /* If pointed-to DIE has a DW_AT_location, evaluate it and return the
+ resulting value. Otherwise, it may have a DW_AT_const_value instead,
+ or it may've been optimized out. */
+ if (baton.data != NULL)
+ return dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
+ baton.data, baton.size, baton.per_cu,
+ byte_offset);
+ else
+ return fetch_const_value_from_synthetic_pointer (die, byte_offset, per_cu,
+ type);
+}
+
/* An implementation of an lval_funcs method to indirect through a
pointer. This handles the synthetic pointer case when needed. */
@@ -2115,6 +2175,7 @@ indirect_pieced_value (struct value *value)
break;
}
+ gdb_assert (piece != NULL);
frame = get_selected_frame (_("No frame selected."));
/* This is an offset requested by GDB, such as value subscripts.
@@ -2132,43 +2193,40 @@ indirect_pieced_value (struct value *value)
TYPE_LENGTH (type), byte_order);
byte_offset += piece->v.ptr.offset;
- gdb_assert (piece);
- baton
- = dwarf2_fetch_die_loc_sect_off (piece->v.ptr.die, c->per_cu,
- get_frame_address_in_block_wrapper,
- frame);
+ return indirect_synthetic_pointer (piece->v.ptr.die, byte_offset, c->per_cu,
+ frame, type);
+}
- if (baton.data != NULL)
- return dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
- baton.data, baton.size, baton.per_cu,
- byte_offset);
+/* Implementation of the coerce_ref method of lval_funcs for synthetic C++
+ references. */
- {
- struct obstack temp_obstack;
- struct cleanup *cleanup;
- const gdb_byte *bytes;
- LONGEST len;
- struct value *result;
-
- obstack_init (&temp_obstack);
- cleanup = make_cleanup_obstack_free (&temp_obstack);
-
- bytes = dwarf2_fetch_constant_bytes (piece->v.ptr.die, c->per_cu,
- &temp_obstack, &len);
- if (bytes == NULL)
- result = allocate_optimized_out_value (TYPE_TARGET_TYPE (type));
- else
- {
- if (byte_offset < 0
- || byte_offset + TYPE_LENGTH (TYPE_TARGET_TYPE (type)) > len)
- invalid_synthetic_pointer ();
- bytes += byte_offset;
- result = value_from_contents (TYPE_TARGET_TYPE (type), bytes);
- }
+static struct value *
+coerce_pieced_ref (const struct value *value)
+{
+ struct type *type = check_typedef (value_type (value));
- do_cleanups (cleanup);
- return result;
- }
+ if (value_bits_synthetic_pointer (value, value_embedded_offset (value),
+ TARGET_CHAR_BIT * TYPE_LENGTH (type)))
+ {
+ const struct piece_closure *closure
+ = (struct piece_closure *) value_computed_closure (value);
+ struct frame_info *frame
+ = get_selected_frame (_("No frame selected."));
+
+ /* gdb represents synthetic pointers as pieced values with a single
+ piece. */
+ gdb_assert (closure != NULL);
+ gdb_assert (closure->n_pieces == 1);
+
+ return indirect_synthetic_pointer (closure->pieces->v.ptr.die,
+ closure->pieces->v.ptr.offset,
+ closure->per_cu, frame, type);
+ }
+ else
+ {
+ /* Else: not a synthetic reference; do nothing. */
+ return NULL;
+ }
}
static void *
@@ -2206,7 +2264,7 @@ static const struct lval_funcs pieced_value_funcs = {
read_pieced_value,
write_pieced_value,
indirect_pieced_value,
- NULL, /* coerce_ref */
+ coerce_pieced_ref,
check_pieced_synthetic_pointer,
copy_pieced_value_closure,
free_pieced_value_closure