PR 16253 revisited

Last year a patch was submitted/approved/commited to eliminate
symbol_matches_domain which was causing this problem.  It was later reverted
because it introduced a (severe) performance regression.

Recap:

(gdb) list
1	enum e {A,B,C} e;
2	int main (void) { return 0; }
3
(gdb) p e
Attempt to use a type name as an expression

The parser attempts to find a symbol named "e" of VAR_DOMAIN.
This gets passed down through lookup_symbol and (eventually) into
block_lookup_symbol_primary, which iterates over the block's dictionary
of symbols:

  for (sym = dict_iter_name_first (block->dict, name, &dict_iter);
       sym != NULL;
       sym = dict_iter_name_next (name, &dict_iter))
    {
      if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
                                 SYMBOL_DOMAIN (sym), domain))
        return sym;
    }

The problem here is that we have a symbol named "e" in both STRUCT_DOMAIN
and VAR_DOMAIN, and for languages like C++, Java, and Ada, where a tag name
may be used as an implicit typedef of the type, symbol_matches_domain ignores
the difference between VAR_DOMAIN and STRUCT_DOMAIN.  As it happens, the
STRUCT_DOMAIN symbol is found first, considered a match, and that symbol is
returned to the parser, eliciting the (now dreaded) error message.

Since this bug exists specifically because we have both STRUCT and VAR_DOMAIN
symbols in a given block/CU, this patch rather simply/naively changes
block_lookup_symbol_primary so that it continues to search for an exact
domain match on the symbol if symbol_matches_domain returns a symbol
which does not exactly match the requested domain.

This "fixes" the immediate problem, but admittedly might uncover other,
related bugs.  [Paranoia?] However, it causes no regressions (functional
or performance) in the test suite.  A similar change has been made
to block_lookup_symbol for other cases in which this bug might appear.

The tests from the previous submission have been resurrected and updated.
However since we can still be given a matching symbol with a different domain
than requested, we cannot say that a symbol "was not found."  The error
messages today will still be the (dreaded) "Attempt to use a type name..."

ChangeLog

	PR 16253
	* block.c (block_lookup_symbol): For non-function blocks,
	continue to search for a symbol with an exact domain match
	Otherwise, return any previously found "best domain" symbol.
	(block_lookup_symbol_primary): Likewise.

testsuite/ChangeLog

	PR 16253
	* gdb.cp/var-tag-2.cc: New file.
	* gdb.cp/var-tag-3.cc: New file.
	* gdb.cp/var-tag-4.cc: New file.
	* gdb.cp/var-tag.cc: New file.
	* gdb.cp/var-tag.exp: New file.
This commit is contained in:
Keith Seitz 2015-06-26 10:27:45 -07:00
parent fc637f04c7
commit ee93cd5e1e
8 changed files with 259 additions and 6 deletions

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@ -1,3 +1,12 @@
2015-06-26 Keith Seitz <keiths@redhat.com>
Doug Evans <dje@google.com>
PR 16253
* block.c (block_lookup_symbol): For non-function blocks,
continue to search for a symbol with an exact domain match
Otherwise, return any previously found "best domain" symbol.
(block_lookup_symbol_primary): Likewise.
2015-06-26 Patrick Palka <patrick@parcs.ath.cx>
* NEWS: Mention the new option "history remove-duplicates".

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@ -739,13 +739,21 @@ block_lookup_symbol (const struct block *block, const char *name,
if (!BLOCK_FUNCTION (block))
{
struct symbol *other = NULL;
ALL_BLOCK_SYMBOLS_WITH_NAME (block, name, iter, sym)
{
if (SYMBOL_DOMAIN (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,
make sure there is no "better" matching symbol, i.e., one with
exactly the same domain. PR 16253. */
if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
SYMBOL_DOMAIN (sym), domain))
return sym;
other = sym;
}
return NULL;
return other;
}
else
{
@ -753,7 +761,10 @@ block_lookup_symbol (const struct block *block, const char *name,
list; this loop makes sure to take anything else other than
parameter symbols first; it only uses parameter symbols as a
last resort. Note that this only takes up extra computation
time on a match. */
time on a match.
It's hard to define types in the parameter list (at least in
C/C++) so we don't do the same PR 16253 hack here that is done
for the !BLOCK_FUNCTION case. */
struct symbol *sym_found = NULL;
@ -779,23 +790,31 @@ struct symbol *
block_lookup_symbol_primary (const struct block *block, const char *name,
const domain_enum domain)
{
struct symbol *sym;
struct symbol *sym, *other;
struct dict_iterator dict_iter;
/* Verify BLOCK is STATIC_BLOCK or GLOBAL_BLOCK. */
gdb_assert (BLOCK_SUPERBLOCK (block) == NULL
|| BLOCK_SUPERBLOCK (BLOCK_SUPERBLOCK (block)) == NULL);
other = NULL;
for (sym = dict_iter_name_first (block->dict, name, &dict_iter);
sym != NULL;
sym = dict_iter_name_next (name, &dict_iter))
{
if (SYMBOL_DOMAIN (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,
make sure there is no "better" matching symbol, i.e., one with
exactly the same domain. PR 16253. */
if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
SYMBOL_DOMAIN (sym), domain))
return sym;
other = sym;
}
return NULL;
return other;
}
/* See block.h. */

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@ -1,3 +1,13 @@
2015-06-26 Keith Seitz <keiths@redhat.com>
Doug Evans <dje@google.com>
PR 16253
* gdb.cp/var-tag-2.cc: New file.
* gdb.cp/var-tag-3.cc: New file.
* gdb.cp/var-tag-4.cc: New file.
* gdb.cp/var-tag.cc: New file.
* gdb.cp/var-tag.exp: New file.
2015-06-26 Patrick Palka <patrick@parcs.ath.cx>
* gdb.base/history-duplicates.exp: New test.

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@ -0,0 +1,22 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2015 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* This object is in a separate file so that its debug info is not
expanded at startup. Once debug info is expanded we are no longer
exercising block_lookup_symbol, and instead are exercising
block_lookup_symbol_primary. */
enum E2 {a2, b2, c2} E2;

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@ -0,0 +1,22 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2015 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* This object is in a separate file so that its debug info is not
expanded at startup. Once debug info is expanded we are no longer
exercising block_lookup_symbol, and instead are exercising
block_lookup_symbol_primary. */
struct S2 {} S2;

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@ -0,0 +1,22 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2015 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* This object is in a separate file so that its debug info is not
expanded at startup. Once debug info is expanded we are no longer
exercising block_lookup_symbol, and instead are exercising
block_lookup_symbol_primary. */
union U2 {int a; char b;} U2;

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@ -0,0 +1,44 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2014 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
int global = 3;
class C {
public:
struct C1 {} C1;
enum E1 {a1, b1, c1} E1;
union U1 {int a1; char b1;} U1;
C () : E1 (b1) {}
void global (void) const {}
int f (void) const { global (); return 0; }
} C;
struct S {} S;
enum E {a, b, c} E;
union U {int a; char b;} U;
class CC {} cc;
struct SS {} ss;
enum EE {ea, eb, ec} ee;
union UU {int aa; char bb;} uu;
int
main (void)
{
return C.f ();
}

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@ -0,0 +1,105 @@
# Copyright 2014, 2015 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# This file is part of the gdb testsuite
# Test expressions in which variable names shadow tag names.
if {[skip_cplus_tests]} { continue }
standard_testfile var-tag.cc var-tag-2.cc var-tag-3.cc var-tag-4.cc
if {[prepare_for_testing $testfile.exp $testfile \
[list $srcfile $srcfile2 $srcfile3 $srcfile4] {debug c++}]} {
return -1
}
proc do_global_tests {lang} {
set invalid_print "Attempt to use a type name as an expression"
set ptypefmt "type = (class|enum|union|struct) %s {.*}"
with_test_prefix $lang {
gdb_test_no_output "set language $lang"
gdb_test "ptype C" "type = class C {.*}"
gdb_test "print E" "= a"
gdb_test "ptype E" "type = enum E {.*}"
gdb_test "print S" "= {<No data fields>}"
gdb_test "ptype S" "type = struct S {.*}"
gdb_test "print U" "= {.*}"
gdb_test "ptype U" "type = union U {.*}"
gdb_test "print cc" "= {.*}"
gdb_test "ptype cc" "type = class CC {.*}"
gdb_test "print CC" [format $invalid_print "CC"]
gdb_test "ptype CC" [format $ptypefmt "CC"]
gdb_test "print ss" "= {<No data fields>}"
gdb_test "ptype ss" "type = struct SS {.*}"
gdb_test "print SS" [format $invalid_print "SS"]
gdb_test "ptype SS" [format $ptypefmt "SS"]
gdb_test "print ee" "= .*"
gdb_test "ptype ee" "type = enum EE {.*}"
gdb_test "print EE" [format $invalid_print "EE"]
gdb_test "ptype EE" [format $ptypefmt "EE"]
gdb_test "print uu" "= {.*}"
gdb_test "ptype uu" "type = union UU {.*}"
gdb_test "print UU" [format $invalid_print "UU"]
gdb_test "ptype UU" [format $ptypefmt "UU"]
# These tests exercise lookup of symbols using the "quick fns" API.
# Each of them is in a separate CU as once its CU is expanded,
# we're no longer using the quick fns API.
gdb_test "print E2" "= a2"
gdb_test "ptype E2" "type = enum E2 {.*}"
gdb_test "print S2" "= {<No data fields>}"
gdb_test "ptype S2" "type = struct S2 {.*}"
gdb_test "print U2" "= {.*}"
gdb_test "ptype U2" "type = union U2 {.*}"
}
}
# First test expressions when there is no context.
with_test_prefix "before start" {
do_global_tests c++
do_global_tests c
}
# Run to main and test again.
if {![runto_main]} {
perror "couldn't run to main"
continue
}
with_test_prefix "in main" {
do_global_tests c++
do_global_tests c
}
# Run to C::f and test again.
gdb_breakpoint "C::f"
gdb_continue_to_breakpoint "continue to C::f"
with_test_prefix "in C::f" {
do_global_tests c++
do_global_tests c
}
# Another hard-to-guess-the-users-intent bug...
# It would be really nice if we could query the user!
with_test_prefix "global collision" {
gdb_test_no_output "set language c++"
setup_kfail "c++/16463" "*-*-*"
gdb_test "print global" "= 3"
# ... with a simple workaround:
gdb_test "print ::global" "= 3"
}