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


Polite ping. 

On Mon, 2018-06-04 at 14:15 +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 to MI consumer as described in
> the documentation.
> 
> gdb/ChangeLog:
> 
> 	* mi/mi-cmd-var.c: Report an error if varobj is a child of
> dynamic
> 	varobj as stated in documentation.
> 	* varobj.c: New assert.
> 
> gdb/testsuite/Changelog:
> 
> 	* gdb.pythonpy-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                                 |  6 ++
>  gdb/mi/mi-cmd-var.c                           |  5 ++
>  gdb/testsuite/ChangeLog                       |  6 ++
>  .../py-mi-var-info-path-expression.c          | 40 ++++++++++
>  .../py-mi-var-info-path-expression.exp        | 77
> +++++++++++++++++++
>  .../py-mi-var-info-path-expression.py         | 45 +++++++++++
>  gdb/varobj.c                                  |  6 +-
>  7 files changed, 184 insertions(+), 1 deletion(-)
>  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 a292f4c056..fc5edb9a9e 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,9 @@
> +2018-06-04  Jan Vrany  <jan.vrany@fit.cvut.cz>
> +
> +	* mi/mi-cmd-var.c: Report an error if varobj is a child of
> dynamic
> +	varobj as stated in documentation.
> +	* varobj.c: New assert.
> +
>  2018-06-04  Pedro Alves  <palves@redhat.com>
>  
>  	* darwin-nat.c (darwin_ops): Delete.
> diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
> index 38c59c7e66..f278281023 100644
> --- a/gdb/mi/mi-cmd-var.c
> +++ b/gdb/mi/mi-cmd-var.c
> @@ -438,6 +438,11 @@ mi_cmd_var_info_path_expression (const char
> *command, char **argv, int argc)
>  
>    /* Get varobj handle, if a valid var obj name was specified.  */
>    var = varobj_get_handle (argv[0]);
> +
> +  /* -var-info-path-expression is currently not valid for children
> of
> +     a dynamic varobj  */
> +  if (var->parent != nullptr && varobj_is_dynamic_p (var->parent))
> +    error (_("Invalid variable object (child of a dynamic
> varobj)"));
>    
>    const char *path_expr = varobj_get_path_expr (var);
>  
> diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
> index 8cef172a26..d7ac7b0a62 100644
> --- a/gdb/testsuite/ChangeLog
> +++ b/gdb/testsuite/ChangeLog
> @@ -1,3 +1,9 @@
> +2018-06-04  Jan Vrany  <jan.vrany@fit.cvut.cz>
> +
> +	* gdb.pythonpy-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.
> +
>  2018-06-01  Joel Brobecker  <brobecker@adacore.com>
>  
>  	* gdb.ada/bp_fun_addr: New testcase.
> 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..a4a5f37178
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
> @@ -0,0 +1,40 @@
> +/* Implementation of the GDB variable objects API.
> +
> +   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/license
> s/>.  */
> +
> +struct _cons
> +{
> +  struct _cons *slots[2];
> +};
> +
> +#define nil ((struct _cons*)0);
> +
> +int
> +main ()
> +{
> +  struct _cons c1, c2, c3;
> +
> +  c1.slots[0] = nil;
> +  c1.slots[1] = &c2;
> +
> +  c2.slots[0] = nil;
> +  c2.slots[1] = &c3;
> +
> +  c3.slots[0] = nil;
> +  c3.slots[1] = nil;
> +
> +  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..f4aece9156
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
> @@ -0,0 +1,77 @@
> +# 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=\"c1.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\".*chi
> ld=\{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"
> 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..39cb5e2e4a
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
> @@ -0,0 +1,45 @@
> +# 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 gdb
> +import gdb.types
> +
> +class cons_pp(object):
> +  def __init__(self, val):
> +    self._val = val
> +
> +  def to_string(self):
> +    if int(self._val) == 0:
> +      return "nil"
> +    else:
> +      return "(...)"
> +
> +  def children(self):
> +    if int(self._val) == 0:
> +      return []
> +    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)
> \ No newline at end of file
> diff --git a/gdb/varobj.c b/gdb/varobj.c
> index a0df485ae9..87bfd44549 100644
> --- a/gdb/varobj.c
> +++ b/gdb/varobj.c
> @@ -962,9 +962,13 @@ varobj_get_path_expr (const struct varobj *var)
>        /* For root varobjs, we initialize path_expr
>  	 when creating varobj, so here it should be
>  	 child varobj.  */
> -      struct varobj *mutable_var = (struct varobj *) var;
>        gdb_assert (!is_root_p (var));
>  
> +      /* Computation of full rooted expression for children of
> dynamic
> +         varobjs is not supported. */
> +      gdb_assert (!varobj_is_dynamic_p(var->parent));
> +
> +      struct varobj *mutable_var = (struct varobj *) var;
>        mutable_var->path_expr = (*var->root->lang_ops-
> >path_expr_of_child) (var);
>      }
>  


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