gdb_vecs.h: Avoid self move assign
While working on another patch I ran into an issue with unordered_remove (in gdb_vecs.h), where removing the last item of the vector can cause a self move assign. When compiling the C++ standard library in debug mode (with -D_GLIBCXX_DEBUG=1) this causes an error to trigger. I've fixed the issue in this patch and provided a unit test. The provided unit test includes an assignment operator which checks for self move assign, this removes the need to compile with -D_GLIBCXX_DEBUG=1 in order to spot the bug. If you're keen to see the error reported from the C++ standard library then remove operator= from the unit test and recompile GDB with -D_GLIBCXX_DEBUG=1. gdb/ChangeLog: * Makefile.in (SUBDIR_UNITTESTS_SRCS): Add new file to the list. * unittests/vec-utils-selftests.c: New file. * gdbsupport/gdb_vecs.h (unordered_remove): Avoid self move assign. Change-Id: I80247b20cd5212038117db7412865f5e6a9257cd
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@ -1,3 +1,9 @@
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2019-11-10 Andrew Burgess <andrew.burgess@embecosm.com>
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* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add new file to the list.
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* unittests/vec-utils-selftests.c: New file.
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* gdbsupport/gdb_vecs.h (unordered_remove): Avoid self move assign.
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2019-11-10 Tom Tromey <tom@tromey.com>
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* tui/tui-wingeneral.c (tui_unhighlight_win): Use can_box.
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@ -440,6 +440,7 @@ SUBDIR_UNITTESTS_SRCS = \
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unittests/tracepoint-selftests.c \
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unittests/unpack-selftests.c \
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unittests/utils-selftests.c \
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unittests/vec-utils-selftests.c \
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unittests/xml-utils-selftests.c
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SUBDIR_UNITTESTS_OBS = $(patsubst %.c,%.o,$(SUBDIR_UNITTESTS_SRCS))
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@ -51,7 +51,8 @@ unordered_remove (std::vector<T> &vec, typename std::vector<T>::iterator it)
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gdb_assert (it >= vec.begin () && it < vec.end ());
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T removed = std::move (*it);
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*it = std::move (vec.back ());
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if (it != vec.end () - 1)
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*it = std::move (vec.back ());
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vec.pop_back ();
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return removed;
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@ -0,0 +1,66 @@
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/* Self tests for vector utility routines for GDB, the GNU debugger.
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Copyright (C) 2019 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "gdbsupport/common-defs.h"
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#include "gdbsupport/selftest.h"
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#include "gdbsupport/gdb_vecs.h"
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namespace selftests {
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namespace vector_utils_tests {
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static void
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unordered_remove_tests ()
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{
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/* Create vector with a single object in, and then remove that object.
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This test was added after a bug was discovered where unordered_remove
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would cause a self move assign. If the C++ standard library is
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compiled in debug mode (by passing -D_GLIBCXX_DEBUG=1) and the
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operator= is removed from struct obj this test used to fail with an
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error from the C++ standard library. */
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struct obj
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{
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std::vector<void *> var;
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obj &operator= (const obj &other)
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{
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if (this == &other)
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error (_("detected self move assign"));
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this->var = other.var;
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return *this;
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}
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};
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std::vector<obj> v;
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v.emplace_back ();
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auto it = v.end () - 1;
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unordered_remove (v, it);
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SELF_CHECK (v.empty ());
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}
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} /* namespace vector_utils_tests */
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} /* amespace selftests */
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void
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_initialize_vec_utils_selftests ()
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{
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selftests::register_test
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("unordered_remove",
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selftests::vector_utils_tests::unordered_remove_tests);
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}
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