[Bug exp/18285] New: ptype expr-with-xmethod -> SEGV

[Bug exp/18285] New: ptype expr-with-xmethod -> SEGV

[dje at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

            Bug ID: 18285
           Summary: ptype expr-with-xmethod -> SEGV
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: exp
          Assignee: unassigned at sourceware dot org
          Reporter: dje at google dot com

gdb unique-ptr
(gdb) start
(gdb) pt *foo # foo is a std::unique_ptr<> object
-> segv

The problem, I think, is in value_x_unop:

      if (noside == EVAL_AVOID_SIDE_EFFECTS)
        {
          struct type *return_type;

          return_type
            = TYPE_TARGET_TYPE (check_typedef (value_type (argvec[0])));
=>        return value_zero (return_type, VALUE_LVAL (arg1));
        }
      if (TYPE_CODE (value_type (argvec[0])) == TYPE_CODE_XMETHOD)
        {
          /* Static xmethods are not supported yet.  */
          gdb_assert (static_memfuncp == 0);
          return call_xmethod (argvec[0], 1, argvec + 1);
        }
      else
        return call_function_by_hand (argvec[0], nargs, argvec + 1);

(top-gdb) p argvec[0]->type->main_type->code
$6 = TYPE_CODE_XMETHOD
xmethods don't have TYPE_TARGET_TYPE, it's NULL.

The user would want the result of the ptype command to be the type of the
result of the xmethod, not the type of the xmethod.
Check for xmethods before EVAL_AVOID_SIDE_EFFECTS?
OTOH, the xmethod may well have side effects.
Propagate EVAL_AVOID_SIDE_EFFECTS into the xmethod?

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[Bug exp/18285] ptype expr-with-xmethod -> SEGV

[sivachandra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

Siva Chandra <sivachandra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sivachandra at gmail dot com

--- Comment #1 from Siva Chandra <sivachandra at gmail dot com> ---
Could we extend the xmethod API to add a method XMethodWorker.return_type() and
use the returned gdb.Type object to evaluate TYPE_TARGET_TYPE of an xmethod
value?

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[Bug exp/18285] ptype expr-with-xmethod -> SEGV

[dje at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

--- Comment #2 from dje at google dot com ---
A return_type method sounds good to me.

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[Bug exp/18285] ptype expr-with-xmethod -> SEGV

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

--- Comment #3 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Doug Evans <devans@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2ce1cdbf84ce883b992bc8ffec3d29b4da229b72

commit 2ce1cdbf84ce883b992bc8ffec3d29b4da229b72
Author: Doug Evans <dje@google.com>
Date:   Wed Apr 29 13:24:21 2015 -0700

    PR python/18285

    gdb/ChangeLog:

        PR python/18285
        * NEWS: Document new gdb.XMethodWorker.get_result_type method.
        * eval.c (evaluate_subexp_standard) <OP_FUNCALL>: Handle
        EVAL_AVOID_SIDE_EFFECTS for xmethods.
        * extension-priv.h (struct extension_language_ops)
        <get_xmethod_result_type>: New member.
        * extension.c (get_xmethod_result_type): New function.
        * extension.h (get_xmethod_result_type): Declare.
        * python/py-xmethods.c (get_result_type_method_name): New static
        global.
        (py_get_result_type_method_name): Ditto.
        (gdbpy_get_xmethod_result_type): New function.
        (gdbpy_initialize_xmethods): Initialize py_get_result_type_method_name.
        * python/python-internal.h (gdbpy_get_xmethod_result_type): Declare.
        * python/python.c (python_extension_ops): Add
        gdbpy_get_xmethod_result_type.
        * python/lib/gdb/xmethod.py (XMethodWorker): Add get_result_type.
        * valarith.c (value_x_binop): Handle EVAL_AVOID_SIDE_EFFECTS for
        xmethods.
        (value_x_unop): Ditto.
        * value.c (result_type_of_xmethod): New function.
        * value.h (result_type_of_xmethod): Declare.

    gdb/testsuite/ChangeLog:

        * gdb.python/py-xmethods.exp: Add ptype tests.
        * gdb.python/py-xmethods.py (E_method_char_worker): Add
        get_result_type method.

    gdb/doc/ChangeLog:

        * python.texi (Xmethod API) <gdb.XMethodWorker.get_result_type>:
        Document.
        (Writing an Xmethod): Add get_result_type to example.

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[Bug exp/18285] ptype expr-with-xmethod -> SEGV

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The gdb-7.9-branch branch has been updated by Doug Evans
<devans@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6b2a76d583a91ae9dad0653c60c91b72f07ff941

commit 6b2a76d583a91ae9dad0653c60c91b72f07ff941
Author: Doug Evans <dje@google.com>
Date:   Tue May 12 09:18:06 2015 -0700

    PR python/18285

    gdb/ChangeLog:

        PR python/18285
        * NEWS: Document new gdb.XMethodWorker.get_result_type method.
        * eval.c (evaluate_subexp_standard) <OP_FUNCALL>: Handle
        EVAL_AVOID_SIDE_EFFECTS for xmethods.
        * extension-priv.h (struct extension_language_ops)
        <get_xmethod_result_type>: New member.
        * extension.c (get_xmethod_result_type): New function.
        * extension.h (get_xmethod_result_type): Declare.
        * python/py-xmethods.c (get_result_type_method_name): New static
        global.
        (py_get_result_type_method_name): Ditto.
        (gdbpy_get_xmethod_result_type): New function.
        (gdbpy_initialize_xmethods): Initialize py_get_result_type_method_name.
        * python/python-internal.h (gdbpy_get_xmethod_result_type): Declare.
        * python/python.c (python_extension_ops): Add
        gdbpy_get_xmethod_result_type.
        * python/lib/gdb/xmethod.py (XMethodWorker): Add get_result_type.
        * valarith.c (value_x_binop): Handle EVAL_AVOID_SIDE_EFFECTS for
        xmethods.
        (value_x_unop): Ditto.
        * value.c (result_type_of_xmethod): New function.
        * value.h (result_type_of_xmethod): Declare.

    gdb/testsuite/ChangeLog:

        * gdb.python/py-xmethods.exp: Add ptype tests.
        * gdb.python/py-xmethods.py (E_method_char_worker): Add
        get_result_type method.

    gdb/doc/ChangeLog:

        * python.texi (Xmethod API) <gdb.XMethodWorker.get_result_type>:
        Document.
        (Writing an Xmethod): Add get_result_type to example.

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[Bug exp/18285] ptype expr-with-xmethod -> SEGV

[dje at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18285

dje at google dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from dje at google dot com ---
patch committed.

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