[PING] [PATCH v5] Fix segfault when invoking -var-info-path-expression on a dynamic varobj

Jan Vrany
2018-07-25T12:33:35Z

Polite ping.

On Mon, 2018-07-02 at 20:20 +0100, Jan Vrany wrote:
> Invoking -var-info-path-expression on a dynamic varobj lead either in wrong
> (nonsense) result or to a segmentation fault in cplus_describe_child().
> This was caused by the fact that varobj_get_path_expr() called
> cplus_path_expr_of_child() ignoring the fact the parent of the variable
> is dynamic. Then, cplus_describe_child() accessed the underlaying C type
> members by index, causing (i) either wrong (nonsense) expression being
> returned (since dynamic child may be completely arbibtrary value)
> or (ii) segmentation fault (in case the index higher than number of
> underlaying C type members.
>
> This fixes the problem by checking whether a varobj is a child of a dynamic
> varobj and, if so, reporting an error as described in documentation.
>
> gdb/ChangeLog:
>
> * varobj.c (varobj_get_path_expr_parent): Report an error if
> parent is a dynamic varobj.
>
> gdb/testsuite/Changelog:
>
> * gdb.python/py-mi-var-info-path-expression.c: New file.
> * gdb.python/py-mi-var-info-path-expression.py: New file.
> * gdb.python/py-mi-var-info-path-expression.exp: New file.
> ---
> gdb/ChangeLog | 5 ++
> gdb/testsuite/ChangeLog | 6 ++
> .../py-mi-var-info-path-expression.c | 62 +++++++++++++
> .../py-mi-var-info-path-expression.exp | 88 +++++++++++++++++++
> .../py-mi-var-info-path-expression.py | 57 ++++++++++++
> gdb/varobj.c | 5 ++
> 6 files changed, 223 insertions(+)
> create mode 100644 gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
> create mode 100644 gdb/testsuite/gdb.python/py-mi-var-info-path-
> expression.exp
> create mode 100644 gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 80626191c9..625c42af36 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,8 @@
> +2018-06-04 Jan Vrany <jan.vrany@fit.cvut.cz>
> +
> + * varobj.c (varobj_get_path_expr_parent): Report an error if
> + parent is a dynamic varobj.
> +
> 2018-06-28 Petr Tesarik <ptesarik@suse.cz>
>
> * symfile.c (add_symbol_file_command, _initialize_symfile): Add
> diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
> index f93eb97d97..0d30ab2793 100644
> --- a/gdb/testsuite/ChangeLog
> +++ b/gdb/testsuite/ChangeLog
> @@ -1,3 +1,9 @@
> +2018-06-04 Jan Vrany <jan.vrany@fit.cvut.cz>
> +
> + * gdb.python/py-mi-var-info-path-expression.c: New file.
> + * gdb.python/py-mi-var-info-path-expression.py: New file.
> + * gdb.python/py-mi-var-info-path-expression.exp: New file.
> +
> 2018-06-28 Richard Bunt <richard.bunt@arm.com>
>
> * gdb.base/watchpoint-hw-attach.c (main): Remove unneeded
> diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
> b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
> new file mode 100644
> index 0000000000..9d6ff126dd
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
> @@ -0,0 +1,62 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + Copyright (C) 1999-2018 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/>. */
> +
> +enum cons_type
> +{
> + type_atom = 0,
> + type_cons = 1
> +};
> +
> +struct atom
> +{
> + int ival;
> +};
> +
> +struct cons
> +{
> + enum cons_type type;
> + union
> + {
> + struct atom atom;
> + struct cons *slots[2];
> + };
> +};
> +
> +#define nil ((struct cons*)0);
> +
> +int
> +main ()
> +{
> + struct cons c1, c2, c3, c4;
> +
> + c1.type = type_cons;
> + c1.slots[0] = &c4;
> + c1.slots[1] = &c2;
> +
> + c2.type = type_cons;
> + c2.slots[0] = nil;
> + c2.slots[1] = &c3;
> +
> + c3.type = type_cons;
> + c3.slots[0] = nil;
> + c3.slots[1] = nil;
> +
> + c4.type = type_atom;
> + c4.atom.ival = 13;
> +
> + return 0; /* next line */
> +}
> diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
> b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
> new file mode 100644
> index 0000000000..b14572f524
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
> @@ -0,0 +1,88 @@
> +# Copyright (C) 2008-2018 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/>.
> +
> +# Tests whether -var-info-path-expression fails as documented when
> +# invoked on a dynamic varobj.
> +
> +load_lib mi-support.exp
> +set MIFLAGS "-i=mi"
> +
> +gdb_exit
> +if {[mi_gdb_start]} {
> + continue
> +}
> +
> +#
> +# Start here
> +#
> +standard_testfile
> +
> +if {[gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable {debug}] !=
> "" } {
> + return -1
> +}
> +
> +mi_gdb_test "source ${srcdir}/${subdir}/${testfile}.py" \
> + ".*\\^done" \
> + "load python file"
> +
> +mi_gdb_test "-enable-pretty-printing" \
> + "\\^done" \
> + "-enable-pretty-printing"
> +
> +mi_gdb_test "set python print-stack full" \
> + ".*\\^done" \
> + "set python print-stack full"
> +
> +
> +mi_run_to_main
> +
> +
> +mi_continue_to_line [gdb_get_line_number "next line" ${srcfile}] \
> + "step to breakpoint"
> +
> +mi_gdb_test "-var-create c1 * &c1" \
> + "\\^done.*" \
> + "-var-create c1 * &c1"
> +
> +mi_gdb_test "-var-info-path-expression c1" \
> + "\\^done,path_expr=\"&c1\"" \
> + "-var-info-path-expression c1"
> +
> +mi_gdb_test "-var-list-children c1" \
> + "\\^done,numchild=\"2\",children=.child=\{name=\"c1.car\".*child=\{name=\"c
> 1.cdr\".*" \
> + "-var-list-children c1"
> +
> +mi_gdb_test "-var-info-path-expression c1.cdr" \
> + "\\^error,msg=\".*\"" \
> + "-var-info-path-expression c1.cdr"
> +
> +mi_gdb_test "-var-list-children c1.cdr" \
> + "\\^done,numchild=\"2\",children=.child=\{name=\"c1.cdr.car\".*child=\{name
> =\"c1.cdr.cdr\".*" \
> + "-var-list-children c1.cdr"
> +
> +mi_gdb_test "-var-info-path-expression c1.cdr.cdr" \
> + "\\^error,msg=\".*\"" \
> + "-var-info-path-expression c1.cdr.cdr"
> +
> +mi_gdb_test "-var-list-children c1.car" \
> + "\\^done,numchild=\"1\",children=.child=\{name=\"c1.car.atom\".*" \
> + "-var-list-children c1.car"
> +
> +mi_gdb_test "-var-list-children c1.car.atom" \
> + "\\^done,numchild=\"1\",children=.child=\{name=\"c1.car.atom.ival\".*" \
> + "-var-list-children c1.car.atom"
> +
> +mi_gdb_test "-var-info-path-expression c1.car.atom.ival" \
> + "\\^error,msg=\".*\"" \
> + "-var-info-path-expression c1.car.atom.ival"
> diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
> b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
> new file mode 100644
> index 0000000000..c2f5897180
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
> @@ -0,0 +1,57 @@
> +# Copyright (C) 2008-2018 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/>.
> +
> +import sys
> +import gdb
> +import gdb.types
> +
> +# Following is for Python 3 compatibility...
> +if sys.version_info[0] > 2:
> + long = int
> +
> +
> +class cons_pp(object):
> + def __init__(self, val):
> + self._val = val
> +
> + def to_string(self):
> + if long(self._val) == 0:
> + return "nil"
> + elif long(self._val['type']) == 0:
> + return "( . )"
> + else:
> + return "%d" % self._val['atom']['ival']
> +
> + def children(self):
> + if long(self._val) == 0:
> + return []
> + elif long(self._val['type']) == 0:
> + return [
> + ('atom', self._val['atom'])
> + ]
> + else:
> + return [
> + ('car' , self._val["slots"][0]),
> + ('cdr' , self._val["slots"][1]),
> + ]
> +
> +def cons_pp_lookup(val):
> + if str(val.type) == 'struct cons *':
> + return cons_pp(val)
> + else:
> + return None
> +
> +del gdb.pretty_printers[1:]
> +gdb.pretty_printers.append(cons_pp_lookup)
> diff --git a/gdb/varobj.c b/gdb/varobj.c
> index 02441410e8..af607963b4 100644
> --- a/gdb/varobj.c
> +++ b/gdb/varobj.c
> @@ -948,6 +948,11 @@ varobj_get_path_expr_parent (const struct varobj *var)
> while (!is_root_p (parent) && !is_path_expr_parent (parent))
> parent = parent->parent;
>
> + /* Computation of full rooted expression for children of dynamic
> + varobjs is not supported. */
> + if (varobj_is_dynamic_p (parent))
> + error (_("Invalid variable object (child of a dynamic varobj)"));
> +
> return parent;
> }
>