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replace_typedefs: handle templates in namespaces

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GDB currently crashes with infinite recursion, if you set a breakpoint
on a function inside a namespace that includes a template on its fully
qualified name, and, the template's name is also used as typedef in
the global scope that expands to a name that includes the template
name in its qualified name.  For example, from the testcase added by
this commit:

 namespace NS1 { namespace NS2 {

 template<typename T> struct Templ1
 {
   T x;

   Templ1 (object_p) {}
 }} // namespace NS1::NS2

 using Templ1 = NS1::NS2::Templ1<unsigned>;

Setting a breakpoint like so:

(gdb) break NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*)

Results in infinite recursion, with this cycle (started by
cp_canonicalize_string_full) repeating until the stack is exhausted:

 ...
 #1709 0x000000000055533c in inspect_type (info=0x38ff720, ret_comp=0xd83be10, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:267
 #1710 0x0000000000555a6f in replace_typedefs (info=0x38ff720, ret_comp=0xd83be10, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:475
 #1711 0x0000000000555a36 in replace_typedefs (info=0x38ff720, ret_comp=0xd83be70, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:470
 #1712 0x0000000000555800 in replace_typedefs_qualified_name (info=0x38ff720, ret_comp=0xd839470, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:389
 #1713 0x0000000000555a8c in replace_typedefs (info=0x38ff720, ret_comp=0xd839470, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:479
 ...

The demangle component tree for that symbol name looks like this:

d_dump tree for NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*):
typed name
  qualified name
    name 'NS1'
    qualified name
      name 'NS2'
      qualified name
        template                  <<<<<<<<<<
          name 'Templ1'
          template argument list
            builtin type int
        name 'Templ1'
  function type
    argument list
      pointer
        qualified name
          name 'NS1'
          qualified name
            name 'NS2'
            name 'object'

The recursion starts at replace_typedefs_qualified_name, which doesn't
handle the "template" node, and thus doesn't realize that the template
name actually has the fully qualified name NS1::NS2::Templ1.
replace_typedefs_qualified_name calls into replace_typedefs on the
template node, and that ends up in inspect_type looking up for a
symbol named "Templ1", which finds the global namespace typedef, which
itself expands to NS1::NS2::Templ1.  GDB then tries replacing typedefs
in that newly expanded name, which ends up again in
replace_typedefs_qualified_name, trying to expand a fully qualified
name with "NS::NS2::Templ1<unsigned>" in its name, which results in
recursion whenever the template node is reached.

Fix this by teaching replace_typedefs_qualified_name how to handle
template nodes.  It needs handling in two places: the first spot
handles the symbol above; the second spot handles a symbol like this,
from the new test:

(gdb) b NS1::NS2::grab_it(NS1::NS2::Templ1<int>*)
d_dump tree for NS1::NS2::grab_it(NS1::NS2::Templ1<int>*):
typed name
  qualified name
    name 'NS1'
    qualified name
      name 'NS2'
      name 'grab_it'
  function type
    argument list
      pointer
        qualified name
          name 'NS1'
          qualified name
            name 'NS2'
            template             <<<<<<<<
              name 'Templ1'
              template argument list
                builtin type int

What's different in this case is that the template node appears on the
right child node of a qualified name, instead of on the left child.

The testcase includes a test that checks whether template aliases are
correctly replaced by GDB too.  That fails with GCC due to GCC PR
95437, which makes GDB not know about a typedef for
"NS1::NS2::AliasTempl<int>".  GCC emits a typedef named
"NS1::NS2::AliasTempl" instead, with no template parameter info.  The
test passes with Clang (5.0.2 at least).  See more details here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95437

gdb/ChangeLog:
2020-05-30  Pedro Alves  <palves@redhat.com>

	* cp-support.c (replace_typedefs_template): New.
	(replace_typedefs_qualified_name): Handle
	DEMANGLE_COMPONENT_TEMPLATE.

gdb/testsuite/ChangeLog:
2020-05-30  Pedro Alves  <palves@redhat.com>

	* gdb.linespec/cp-replace-typedefs-ns-template.cc: New.
	* gdb.linespec/cp-replace-typedefs-ns-template.exp: New.
This commit is contained in:
Pedro Alves 2020-05-30 14:20:10 +01:00
parent bb6e246742
commit f68f85b52b
5 changed files with 305 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
gdb/ChangeLog
View File

@ -1,3 +1,9 @@
2020-05-30 Pedro Alves <palves@redhat.com>
* cp-support.c (replace_typedefs_template): New.
(replace_typedefs_qualified_name): Handle
DEMANGLE_COMPONENT_TEMPLATE.
2020-05-29 Simon Marchi <simon.marchi@efficios.com>
* dwarf2/comp-unit.c, dwarf2/comp-unit.h, dwarf2/index-cache.c,

76
gdb/cp-support.c
View File

@ -294,6 +294,42 @@ inspect_type (struct demangle_parse_info *info,
return 0;
}
/* Helper for replace_typedefs_qualified_name to handle
DEMANGLE_COMPONENT_TEMPLATE. TMPL is the template node. BUF is
the buffer that holds the qualified name being built by
replace_typedefs_qualified_name. REPL is the node that will be
rewritten as a DEMANGLE_COMPONENT_NAME node holding the 'template
plus template arguments' name with typedefs replaced. */
static bool
replace_typedefs_template (struct demangle_parse_info *info,
string_file &buf,
struct demangle_component *tmpl,
struct demangle_component *repl,
canonicalization_ftype *finder,
void *data)
{
demangle_component *tmpl_arglist = d_right (tmpl);
/* Replace typedefs in the template argument list. */
replace_typedefs (info, tmpl_arglist, finder, data);
/* Convert 'template + replaced template argument list' to a string
and replace the REPL node. */
gdb::unique_xmalloc_ptr<char> tmpl_str = cp_comp_to_string (tmpl, 100);
if (tmpl_str == nullptr)
{
/* If something went astray, abort typedef substitutions. */
return false;
}
buf.puts (tmpl_str.get ());
repl->type = DEMANGLE_COMPONENT_NAME;
repl->u.s_name.s = obstack_strdup (&info->obstack, buf.string ());
repl->u.s_name.len = buf.size ();
return true;
}
/* Replace any typedefs appearing in the qualified name
(DEMANGLE_COMPONENT_QUAL_NAME) represented in RET_COMP for the name parse
given in INFO. */
@ -314,6 +350,29 @@ replace_typedefs_qualified_name (struct demangle_parse_info *info,
substituted name. */
while (comp->type == DEMANGLE_COMPONENT_QUAL_NAME)
{
if (d_left (comp)->type == DEMANGLE_COMPONENT_TEMPLATE)
{
/* Convert 'template + replaced template argument list' to a
string and replace the top DEMANGLE_COMPONENT_QUAL_NAME
node. */
if (!replace_typedefs_template (info, buf,
d_left (comp), d_left (ret_comp),
finder, data))
return;
buf.clear ();
d_right (ret_comp) = d_right (comp);
comp = ret_comp;
/* Fallback to DEMANGLE_COMPONENT_NAME processing. We want
to call inspect_type for this template, in case we have a
template alias, like:
template<typename T> using alias = base<int, t>;
in which case we want inspect_type to do a replacement like:
alias<int> -> base<int, int>
*/
}
if (d_left (comp)->type == DEMANGLE_COMPONENT_NAME)
{
struct demangle_component newobj;
@ -370,11 +429,20 @@ replace_typedefs_qualified_name (struct demangle_parse_info *info,
comp = d_right (comp);
}
/* If the next component is DEMANGLE_COMPONENT_NAME, save the qualified
name assembled above and append the name given by COMP. Then use this
reassembled name to check for a typedef. */
/* If the next component is DEMANGLE_COMPONENT_TEMPLATE or
DEMANGLE_COMPONENT_NAME, save the qualified name assembled above
and append the name given by COMP. Then use this reassembled
name to check for a typedef. */
if (comp->type == DEMANGLE_COMPONENT_NAME)
if (comp->type == DEMANGLE_COMPONENT_TEMPLATE)
{
/* Replace the top (DEMANGLE_COMPONENT_QUAL_NAME) node with a
DEMANGLE_COMPONENT_NAME node containing the whole name. */
if (!replace_typedefs_template (info, buf, comp, ret_comp, finder, data))
return;
inspect_type (info, ret_comp, finder, data);
}
else if (comp->type == DEMANGLE_COMPONENT_NAME)
{
buf.write (comp->u.s_name.s, comp->u.s_name.len);

5
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2020-05-30 Pedro Alves <palves@redhat.com>
* gdb.linespec/cp-replace-typedefs-ns-template.cc: New.
* gdb.linespec/cp-replace-typedefs-ns-template.exp: New.
2020-05-29 Gary Benson <gbenson@redhat.com>
* gdb.compile/compile-cplus.exp (additional_flags): Also

101
gdb/testsuite/gdb.linespec/cp-replace-typedefs-ns-template.cc Normal file
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@ -0,0 +1,101 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2019-2020 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/>. */
namespace NS1 {
namespace NS2 {
struct object
{
object ()
{
}
};
typedef object *object_p;
template<typename T>
struct Templ1
{
explicit Templ1 (object_p)
{
}
template<typename I>
static void
static_method (object_p)
{
}
};
template<typename T, typename U>
struct Templ2
{
explicit Templ2 (object_p)
{
}
template<typename I>
static void
static_method (object_p)
{
}
};
template<typename T> using AliasTempl = Templ2<int, T>;
typedef Templ1<int> int_Templ1_t;
void
object_p_func (object_p)
{
}
void
int_Templ1_t_func (int_Templ1_t *)
{
}
} // namespace NS2
} // namespace NS1
/* These typedefs have the same name as some of the components within
NS1 that they alias to, on purpose, to try to confuse GDB and cause
recursion. */
using NS2 = int;
using object = NS1::NS2::object;
using Templ1 = NS1::NS2::Templ1<unsigned>;
using Templ2 = NS1::NS2::Templ2<long, long>;
using AliasTempl = NS1::NS2::AliasTempl<int>;
NS2 ns2_int = 0;
object obj;
Templ1 templ1 (0);
NS1::NS2::int_Templ1_t int_templ1 (0);
AliasTempl alias (0);
int
main ()
{
NS1::NS2::Templ1<int>::static_method<int> (0);
NS1::NS2::AliasTempl<int>::static_method<int> (0);
NS1::NS2::object_p_func (0);
NS1::NS2::int_Templ1_t_func (0);
return 0;
}

121
gdb/testsuite/gdb.linespec/cp-replace-typedefs-ns-template.exp Normal file
View File

@ -0,0 +1,121 @@
# Copyright 2020 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 tests GDB's ability to replace typedefs in C++ symbols
# when setting breakpoints, particularly around templates in
# namespaces.
load_lib completion-support.exp
standard_testfile .cc
if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
{debug c++ additional_flags=-std=c++11}]} {
return -1
}
# Disable the completion limit for the whole testcase.
gdb_test_no_output "set max-completions unlimited"
# Confirm that the important global namespace typedefs were indeed
# emited in the debug info.
gdb_test "ptype NS2" "type = int"
gdb_test "ptype object" "type = struct NS1::NS2::object {.*"
gdb_test "ptype Templ1" "type = struct NS1::NS2::Templ1<unsigned int> .*"
gdb_test "ptype AliasTempl" "type = struct NS1::NS2::Templ2<int, int> .*"
# Wrapper around check_bp_locations_match_list that expect a single
# location in the set breakpoint, instead of a list of locations. If
# the set location isn't specified, then it is assumed to be the exact
# same as the input location.
proc check_bp {location_in {location_out ""}} {
if {$location_out == ""} {
set location_out $location_in
}
check_bp_locations_match_list "b $location_in" [list $location_out]
}
# These used to crash GDB with infinite recursion because GDB would
# confuse the "Templ1" typedef in the global namespace with the "Templ1"
# template in within NS1::NS2.
test_gdb_complete_unique \
"break NS1::NS2::Templ1<int>::Tem" \
"break NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*)"
check_bp "NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*)"
# Similar test, but without a template. This would not crash.
test_gdb_complete_unique \
"break NS1::NS2::object::obj" \
"break NS1::NS2::object::object()"
check_bp "NS1::NS2::object::object()"
# Test some non-template typedef replacing within a namespace.
test_gdb_complete_unique \
"break NS1::NS2::object_p_f" \
"break NS1::NS2::object_p_func(NS1::NS2::object*)"
check_bp \
"NS1::NS2::object_p_func(NS1::NS2::object_p)" \
"NS1::NS2::object_p_func(NS1::NS2::object*)"
# Make sure the "NS2" in the template argument list is resolved as
# being a global typedef for int.
foreach loc {
"NS1::NS2::Templ1<int>::static_method<int>(NS1::NS2::object*)"
"NS1::NS2::Templ1<int>::static_method<NS2>(NS1::NS2::object*)"
"NS1::NS2::Templ1<NS2>::static_method<int>(NS1::NS2::object*)"
"NS1::NS2::Templ1<NS2>::static_method<NS2>(NS1::NS2::object*)"
} {
check_bp $loc "NS1::NS2::Templ1<int>::static_method<int>(NS1::NS2::object*)"
}
foreach loc {
"NS1::NS2::Templ2<int, int>::static_method<int>(NS1::NS2::object*)"
"NS1::NS2::Templ2<int, int>::static_method<int>(NS1::NS2::object_p)"
} {
check_bp $loc "NS1::NS2::Templ2<int, int>::static_method<int>(NS1::NS2::object*)"
}
# Check that GDB expands the "NS1::NS2::AliasTempl<int>" as
# "NS1::NS2::Templ2<int, int>".
foreach loc {
"NS1::NS2::AliasTempl<int>::static_method<int>(NS1::NS2::object*)"
"NS1::NS2::AliasTempl<int>::static_method<int>(NS1::NS2::object_p)"
} {
if [test_compiler_info gcc*] {
# While Clang emits "AliasTempl<int>" (etc.) typedefs, GCC
# emits "AliasTempl" typedefs with no template parameter info.
setup_xfail gcc/95437 *-*-*
}
check_bp $loc "NS1::NS2::Templ2<int, int>::static_method<int>(NS1::NS2::object*)"
# Check that setting the breakpoint with GCC really failed,
# instead of succeeding with e.g., "AliasTempl<int>" preserved in
# the location text. If that ever happens, we'll need to update
# these tests.
if [test_compiler_info gcc*] {
check_setting_bp_fails "b $loc"
}
}
# Check typedef substitution in a template in a qualified name in a
# function parameter list. These used to crash GDB with recursion
# around "Templ1", because there's a "Templ1" typedef in the global
# namespace.
foreach loc {
"NS1::NS2::int_Templ1_t_func(NS1::NS2::int_Templ1_t*)"
"NS1::NS2::int_Templ1_t_func(NS1::NS2::Templ1<int>*)"
} {
check_bp $loc "NS1::NS2::int_Templ1_t_func(NS1::NS2::Templ1<int>*)"
}