From cf57ad6d61771f608079f31db10a93872a4553c5 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Fri, 8 Nov 2019 23:39:14 +0000 Subject: [PATCH] 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 --- gdb/ChangeLog | 6 +++ gdb/Makefile.in | 1 + gdb/gdbsupport/gdb_vecs.h | 3 +- gdb/unittests/vec-utils-selftests.c | 66 +++++++++++++++++++++++++++++ 4 files changed, 75 insertions(+), 1 deletion(-) create mode 100644 gdb/unittests/vec-utils-selftests.c diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 6f377f3347..b9d5f21e22 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2019-11-10 Andrew Burgess + + * 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. + 2019-11-10 Tom Tromey * tui/tui-wingeneral.c (tui_unhighlight_win): Use can_box. diff --git a/gdb/Makefile.in b/gdb/Makefile.in index 4f431c3c84..9ca77f6412 100644 --- a/gdb/Makefile.in +++ b/gdb/Makefile.in @@ -440,6 +440,7 @@ SUBDIR_UNITTESTS_SRCS = \ unittests/tracepoint-selftests.c \ unittests/unpack-selftests.c \ unittests/utils-selftests.c \ + unittests/vec-utils-selftests.c \ unittests/xml-utils-selftests.c SUBDIR_UNITTESTS_OBS = $(patsubst %.c,%.o,$(SUBDIR_UNITTESTS_SRCS)) diff --git a/gdb/gdbsupport/gdb_vecs.h b/gdb/gdbsupport/gdb_vecs.h index e87ebe26e9..e8af624770 100644 --- a/gdb/gdbsupport/gdb_vecs.h +++ b/gdb/gdbsupport/gdb_vecs.h @@ -51,7 +51,8 @@ unordered_remove (std::vector &vec, typename std::vector::iterator it) gdb_assert (it >= vec.begin () && it < vec.end ()); T removed = std::move (*it); - *it = std::move (vec.back ()); + if (it != vec.end () - 1) + *it = std::move (vec.back ()); vec.pop_back (); return removed; diff --git a/gdb/unittests/vec-utils-selftests.c b/gdb/unittests/vec-utils-selftests.c new file mode 100644 index 0000000000..823bbb61c2 --- /dev/null +++ b/gdb/unittests/vec-utils-selftests.c @@ -0,0 +1,66 @@ +/* Self tests for vector utility routines for GDB, the GNU debugger. + + Copyright (C) 2019 Free Software Foundation, Inc. + + This file is part of GDB. + + 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 . */ + +#include "gdbsupport/common-defs.h" +#include "gdbsupport/selftest.h" + +#include "gdbsupport/gdb_vecs.h" + +namespace selftests { +namespace vector_utils_tests { + +static void +unordered_remove_tests () +{ + /* Create vector with a single object in, and then remove that object. + This test was added after a bug was discovered where unordered_remove + would cause a self move assign. If the C++ standard library is + compiled in debug mode (by passing -D_GLIBCXX_DEBUG=1) and the + operator= is removed from struct obj this test used to fail with an + error from the C++ standard library. */ + struct obj + { + std::vector var; + + obj &operator= (const obj &other) + { + if (this == &other) + error (_("detected self move assign")); + this->var = other.var; + return *this; + } + }; + + std::vector v; + v.emplace_back (); + auto it = v.end () - 1; + unordered_remove (v, it); + SELF_CHECK (v.empty ()); +} + +} /* namespace vector_utils_tests */ +} /* amespace selftests */ + +void +_initialize_vec_utils_selftests () +{ + selftests::register_test + ("unordered_remove", + selftests::vector_utils_tests::unordered_remove_tests); +} -- 2.34.1