[pushed] [gdb/symtab] Prefer var def over decl
Sourceware to Gerrit sync (Code Review)
gerrit@gnutoolchain-gerrit.osci.io
Fri Dec 6 17:53:00 GMT 2019
Sourceware to Gerrit sync has submitted this change.
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/29
......................................................................
[gdb/symtab] Prefer var def over decl
Consider the DWARF as generated by gcc with the tentative patch to fix gcc
PR91507 - "wrong debug for completed array with previous incomplete
declaration":
...
<1><f4>: Abbrev Number: 2 (DW_TAG_array_type)
<f5> DW_AT_type : <0xff>
<f9> DW_AT_sibling : <0xff>
<2><fd>: Abbrev Number: 3 (DW_TAG_subrange_type)
<2><fe>: Abbrev Number: 0
<1><ff>: Abbrev Number: 4 (DW_TAG_pointer_type)
<100> DW_AT_byte_size : 8
<101> DW_AT_type : <0x105>
<1><105>: Abbrev Number: 5 (DW_TAG_base_type)
<106> DW_AT_byte_size : 1
<107> DW_AT_encoding : 6 (signed char)
<108> DW_AT_name : (indirect string, offset: 0x19f): char
<1><10c>: Abbrev Number: 6 (DW_TAG_variable)
<10d> DW_AT_name : zzz
<111> DW_AT_decl_file : 1
<112> DW_AT_decl_line : 1
<113> DW_AT_decl_column : 14
<114> DW_AT_type : <0xf4>
<118> DW_AT_external : 1
<118> DW_AT_declaration : 1
<1><118>: Abbrev Number: 2 (DW_TAG_array_type)
<119> DW_AT_type : <0xff>
<11d> DW_AT_sibling : <0x128>
<1><12f>: Abbrev Number: 8 (DW_TAG_variable)
<130> DW_AT_specification: <0x10c>
<134> DW_AT_decl_line : 2
<135> DW_AT_decl_column : 7
<136> DW_AT_type : <0x118>
<13a> DW_AT_location : 9 byte block: 3 30 10 60 0 0 0 0 0 (DW_OP_addr: 601030)
...
The DWARF will result in two entries in the symbol table, a decl with type
char *[] and a def with type char*[2].
When trying to print the value of zzz:
...
$ gdb a.spec.out -batch -ex "p zzz"
...
the decl (rather than the def) will be found in the symbol table, which is
missing the location information, and consequently we get:
...
$1 = 0x601030 <zzz>
...
[ There is a fallback mechanism that finds the address of the variable in the
minimal symbol table, but that's not used here, because the type of the decl
does not specify a size. We could use the symbol size here to get the size
of the type, but that's currently not done: PR exp/24989. Still, fixing that
PR would not fix the generic case, where minimal symbol info is not
available. ]
Fix this by preferring defs over decls when searching in the symbol table.
Build and reg-tested on x86_64-linux.
gdb/ChangeLog:
2019-12-06 Tom de Vries <tdevries@suse.de>
PR symtab/24971
* block.c (best_symbol, better_symbol): New function.
(block_lookup_symbol_primary, block_lookup_symbol): Prefer def over
decl.
gdb/testsuite/ChangeLog:
2019-12-06 Tom de Vries <tdevries@suse.de>
* gdb.dwarf2/varval.exp: Add decl before def test.
Change-Id: Id92326cb8ef9903b121ef9e320658eb565d0f5a9
---
M gdb/ChangeLog
M gdb/block.c
M gdb/testsuite/ChangeLog
M gdb/testsuite/gdb.dwarf2/varval.exp
4 files changed, 123 insertions(+), 10 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 2d60712..55ba844 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2019-12-06 Tom de Vries <tdevries@suse.de>
+
+ PR symtab/24971
+ * block.c (best_symbol, better_symbol): New function.
+ (block_lookup_symbol_primary, block_lookup_symbol): Prefer def over
+ decl.
+
2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdbtypes.h: Define the REFERENCE_SEE_THROUGH_BADNESS value.
diff --git a/gdb/block.c b/gdb/block.c
index a4592e3..b49c548 100644
--- a/gdb/block.c
+++ b/gdb/block.c
@@ -657,6 +657,43 @@
return block_iter_match_step (iterator, name, 0);
}
+/* Return true if symbol A is the best match possible for DOMAIN. */
+
+static bool
+best_symbol (struct symbol *a, const domain_enum domain)
+{
+ return (SYMBOL_DOMAIN (a) == domain
+ && SYMBOL_CLASS (a) != LOC_UNRESOLVED);
+}
+
+/* Return symbol B if it is a better match than symbol A for DOMAIN.
+ Otherwise return A. */
+
+static struct symbol *
+better_symbol (struct symbol *a, struct symbol *b, const domain_enum domain)
+{
+ if (a == NULL)
+ return b;
+ if (b == NULL)
+ return a;
+
+ if (SYMBOL_DOMAIN (a) == domain
+ && SYMBOL_DOMAIN (b) != domain)
+ return a;
+ if (SYMBOL_DOMAIN (b) == domain
+ && SYMBOL_DOMAIN (a) != domain)
+ return b;
+
+ if (SYMBOL_CLASS (a) != LOC_UNRESOLVED
+ && SYMBOL_CLASS (b) == LOC_UNRESOLVED)
+ return a;
+ if (SYMBOL_CLASS (b) != LOC_UNRESOLVED
+ && SYMBOL_CLASS (a) == LOC_UNRESOLVED)
+ return b;
+
+ return a;
+}
+
/* See block.h.
Note that if NAME is the demangled form of a C++ symbol, we will fail
@@ -684,7 +721,9 @@
ALL_BLOCK_SYMBOLS_WITH_NAME (block, lookup_name, iter, sym)
{
- if (SYMBOL_DOMAIN (sym) == domain)
+ /* See comment related to PR gcc/debug/91507 in
+ block_lookup_symbol_primary. */
+ if (best_symbol (sym, domain))
return sym;
/* This is a bit of a hack, but symbol_matches_domain might ignore
STRUCT vs VAR domain symbols. So if a matching symbol is found,
@@ -692,7 +731,7 @@
exactly the same domain. PR 16253. */
if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
SYMBOL_DOMAIN (sym), domain))
- other = sym;
+ other = better_symbol (other, sym, domain);
}
return other;
}
@@ -746,7 +785,34 @@
sym != NULL;
sym = mdict_iter_match_next (lookup_name, &mdict_iter))
{
- if (SYMBOL_DOMAIN (sym) == domain)
+ /* With the fix for PR gcc/debug/91507, we get for:
+ ...
+ extern char *zzz[];
+ char *zzz[ ] = {
+ "abc",
+ "cde"
+ };
+ ...
+ DWARF which will result in two entries in the symbol table, a decl
+ with type char *[] and a def with type char *[2].
+
+ If we return the decl here, we don't get the value of zzz:
+ ...
+ $ gdb a.spec.out -batch -ex "p zzz"
+ $1 = 0x601030 <zzz>
+ ...
+ because we're returning the symbol without location information, and
+ because the fallback that uses the address from the minimal symbols
+ doesn't work either because the type of the decl does not specify a
+ size.
+
+ To fix this, we prefer def over decl in best_symbol and
+ better_symbol.
+
+ In absence of the gcc fix, both def and decl have type char *[], so
+ the only option to make this work is improve the fallback to use the
+ size of the minimal symbol. Filed as PR exp/24989. */
+ if (best_symbol (sym, domain))
return sym;
/* This is a bit of a hack, but symbol_matches_domain might ignore
@@ -755,7 +821,7 @@
exactly the same domain. PR 16253. */
if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
SYMBOL_DOMAIN (sym), domain))
- other = sym;
+ other = better_symbol (other, sym, domain);
}
return other;
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f7447dc..c9f66ad 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-12-06 Tom de Vries <tdevries@suse.de>
+
+ * gdb.dwarf2/varval.exp: Add decl before def test.
+
2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb.cp/rvalue-ref-overload.exp: Minor cleanup.
diff --git a/gdb/testsuite/gdb.dwarf2/varval.exp b/gdb/testsuite/gdb.dwarf2/varval.exp
index 5945910..8f5e16f 100644
--- a/gdb/testsuite/gdb.dwarf2/varval.exp
+++ b/gdb/testsuite/gdb.dwarf2/varval.exp
@@ -55,7 +55,8 @@
var_b_label var_c_label var_p_label var_bad_label \
varval_label var_s_label var_untyped_label \
var_a_abstract_label var_a_concrete_label \
- varval2_label
+ varval2_label varval3_def_label varval3_decl_label \
+ int_array_label int_array_of_1_label
set int_size [get_sizeof "int" -1]
@@ -171,6 +172,32 @@
{DW_AT_location {DW_OP_addr [gdb_target_symbol "var_b"]} SPECIAL_expr}
}
+ int_array_label: DW_TAG_array_type {
+ {DW_AT_type :${int_label}}
+ } {
+ DW_TAG_subrange_type {}
+ }
+ varval3_decl_label: DW_TAG_variable {
+ {DW_AT_name "varval3"}
+ {DW_AT_type :${int_array_label}}
+ {DW_AT_external 1 DW_FORM_flag}
+ {DW_AT_declaration 1 DW_FORM_flag}
+ }
+ int_array_of_1_label: DW_TAG_array_type {
+ {DW_AT_type :${int_label}}
+ } {
+ DW_TAG_subrange_type {
+ {DW_AT_type :$int_label}
+ {DW_AT_upper_bound 0 DW_FORM_data1}
+ }
+ }
+ varval3_def_label: DW_TAG_variable {
+ {DW_AT_name "varval3"}
+ {DW_AT_external 1 DW_FORM_flag}
+ {DW_AT_type :${int_array_of_1_label}}
+ {DW_AT_location {DW_OP_addr [gdb_target_symbol "var_a"]} SPECIAL_expr}
+ }
+
DW_TAG_subprogram {
{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
{DW_AT_type :${int_label}}
@@ -277,19 +304,24 @@
if [prepare_for_testing "failed to prepare" ${executable} [list ${asm_file} ${srcfile}] {}] {
return -1
}
-
- # DW_OP_GNU_variable_value implementation requires a valid frame.
- if ![runto_main] {
- return -1
- }
}
if { [setup_exec 0] == -1 } {
return -1
}
+with_test_prefix "pre-main" {
+ gdb_test "print varval3" "= \\{8\\}" ""
+}
+
+# DW_OP_GNU_variable_value implementation requires a valid frame.
+if ![runto_main] {
+ return -1
+}
+
gdb_test "print varval" "= 8"
gdb_test "print varval2" "= 8"
+gdb_test "print varval3" "= \\{8\\}"
gdb_test "print constval" "= 53"
gdb_test "print mixedval" "= 42"
gdb_test "print pointerval" "= \\(int \\*\\) $hex <var_b>"
@@ -311,6 +343,10 @@
return -1
}
+# DW_OP_GNU_variable_value implementation requires a valid frame.
+if ![runto_main] {
+ return -1
+}
gdb_test "print badval" "value has been optimized out"
gdb_test "print bad_die_val1" \
"invalid dwarf2 offset 0xabcdef11"
--
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: Id92326cb8ef9903b121ef9e320658eb565d0f5a9
Gerrit-Change-Number: 29
Gerrit-PatchSet: 5
Gerrit-Owner: Tom de Vries <tdevries@suse.de>
Gerrit-Reviewer: Andrew Burgess <andrew.burgess@embecosm.com>
Gerrit-Reviewer: Luis Machado <luis.machado@linaro.org>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-Reviewer: Tom de Vries <tdevries@suse.de>
Gerrit-CC: Joel Brobecker <brobecker@adacore.com>
Gerrit-MessageType: merged
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