[PATCH 2/3] struct packed: Unit tests and more operators

Pedro Alves
2022-07-21T15:22:20Z

For PR gdb/29373, I wrote an alternative implementation of struct
packed that uses a gdb_byte array for internal representation, needed
for mingw+clang. While adding that, I wrote some unit tests to make
sure both implementations behave the same. While at it, I implemented
all relational operators. This commit adds said unit tests and
relational operators. The alternative gdb_byte array implementation
will come next.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29373

Change-Id: I023315ee03622c59c397bf4affc0b68179c32374
---
gdb/Makefile.in | 1 +
gdb/unittests/packed-selftests.c | 132 +++++++++++++++++++++++++++++++
gdbsupport/packed.h | 79 +++++++++++-------
3 files changed, 182 insertions(+), 30 deletions(-)
create mode 100644 gdb/unittests/packed-selftests.c

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 57c29a78b7a..aebb7dc5ea3 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -464,6 +464,7 @@ SELFTESTS_SRCS = \
unittests/offset-type-selftests.c \
unittests/observable-selftests.c \
unittests/optional-selftests.c \
+ unittests/packed-selftests.c \
unittests/parallel-for-selftests.c \
unittests/parse-connection-spec-selftests.c \
unittests/path-join-selftests.c \
diff --git a/gdb/unittests/packed-selftests.c b/gdb/unittests/packed-selftests.c
new file mode 100644
index 00000000000..3438a5a2555
--- /dev/null
+++ b/gdb/unittests/packed-selftests.c
@@ -0,0 +1,132 @@
+/* Self tests for packed for GDB, the GNU debugger.
+
+ Copyright (C) 2022 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 <http://www.gnu.org/licenses/>. */
+
+#include "defs.h"
+#include "gdbsupport/selftest.h"
+#include "gdbsupport/packed.h"
+
+namespace selftests {
+namespace packed_tests {
+
+enum test_enum
+{
+ TE_A = 1,
+ TE_B = 2,
+ TE_C = 3,
+ TE_D = 4,
+};
+
+gdb_static_assert (sizeof (packed<test_enum, 1>) == 1);
+gdb_static_assert (sizeof (packed<test_enum, 2>) == 2);
+gdb_static_assert (sizeof (packed<test_enum, 3>) == 3);
+gdb_static_assert (sizeof (packed<test_enum, 4>) == 4);
+
+gdb_static_assert (alignof (packed<test_enum, 1>) == 1);
+gdb_static_assert (alignof (packed<test_enum, 2>) == 1);
+gdb_static_assert (alignof (packed<test_enum, 3>) == 1);
+gdb_static_assert (alignof (packed<test_enum, 4>) == 1);
+
+/* Triviality checks. */
+#define CHECK_TRAIT(TRAIT) \
+ static_assert (std::TRAIT<packed<test_enum, 1>>::value, "")
+
+#if HAVE_IS_TRIVIALLY_COPYABLE
+
+CHECK_TRAIT (is_trivially_copyable);
+CHECK_TRAIT (is_trivially_copy_constructible);
+CHECK_TRAIT (is_trivially_move_constructible);
+CHECK_TRAIT (is_trivially_copy_assignable);
+CHECK_TRAIT (is_trivially_move_assignable);
+
+#endif
+
+#undef CHECK_TRAIT
+
+/* Entry point. */
+
+static void
+run_tests ()
+{
+ typedef packed<unsigned int, 2> packed_2;
+
+ packed_2 p1;
+ packed_2 p2 (0x0102);
+ p1 = 0x0102;
+
+ SELF_CHECK (p1 == p1);
+ SELF_CHECK (p1 == p2);
+ SELF_CHECK (p1 == 0x0102);
+ SELF_CHECK (0x0102 == p1);
+
+ SELF_CHECK (p1 != 0);
+ SELF_CHECK (0 != p1);
+
+ SELF_CHECK (p1 != 0x0103);
+ SELF_CHECK (0x0103 != p1);
+
+ SELF_CHECK (p1 != 0x01020102);
+ SELF_CHECK (0x01020102 != p1);
+
+ SELF_CHECK (p1 != 0x01020000);
+ SELF_CHECK (0x01020000 != p1);
+
+ /* Check truncation. */
+ p1 = 0x030102;
+ SELF_CHECK (p1 == 0x0102);
+ SELF_CHECK (p1 != 0x030102);
+
+ /* Check that the custom std::atomic/packed/T relational operators
+ work as intended. No need for fully comprehensive tests, as all
+ operators are defined in the same way, via a macro. We just want
+ to make sure that we can compare atomic-wrapped packed, with
+ packed, and with the packed underlying type. */
+
+ std::atomic<packed<unsigned int, 2>> atomic_packed_2 (0x0102);
+
+ SELF_CHECK (atomic_packed_2 == atomic_packed_2);
+ SELF_CHECK (atomic_packed_2 == p1);
+ SELF_CHECK (p1 == atomic_packed_2);
+ SELF_CHECK (atomic_packed_2 == 0x0102u);
+ SELF_CHECK (0x0102u == atomic_packed_2);
+
+ SELF_CHECK (atomic_packed_2 >= 0x0102u);
+ SELF_CHECK (atomic_packed_2 <= 0x0102u);
+ SELF_CHECK (atomic_packed_2 > 0u);
+ SELF_CHECK (atomic_packed_2 < 0x0103u);
+ SELF_CHECK (atomic_packed_2 >= 0u);
+ SELF_CHECK (atomic_packed_2 <= 0x0102u);
+ SELF_CHECK (!(atomic_packed_2 > 0x0102u));
+ SELF_CHECK (!(atomic_packed_2 < 0x0102u));
+
+ /* Check std::atomic<packed> truncation behaves the same as without
+ std::atomic. */
+ atomic_packed_2 = 0x030102;
+ SELF_CHECK (atomic_packed_2 == 0x0102u);
+ SELF_CHECK (atomic_packed_2 != 0x030102u);
+}
+
+} /* namespace packed_tests */
+} /* namespace selftests */
+
+void _initialize_packed_selftests ();
+void
+_initialize_packed_selftests ()
+{
+ selftests::register_test ("packed", selftests::packed_tests::run_tests);
+}
diff --git a/gdbsupport/packed.h b/gdbsupport/packed.h
index 53164a9e0c3..d721b02c056 100644
--- a/gdbsupport/packed.h
+++ b/gdbsupport/packed.h
@@ -19,6 +19,7 @@
#define PACKED_H

#include "traits.h"
+#include <atomic>

/* Each instantiation and full specialization of the packed template
defines a type that behaves like a given scalar type, but that has
@@ -68,37 +69,55 @@ struct ATTRIBUTE_GCC_STRUCT packed
T m_val : (Bytes * HOST_CHAR_BIT) ATTRIBUTE_PACKED;
};

-/* Add some comparisons between std::atomic<packed<T>> and T. We need
- this because the regular comparisons would require two implicit
- conversions to go from T to std::atomic<packed<T>>:
-
- T -> packed<T>
- packed<T> -> std::atomic<packed<T>>
-
- and C++ only does one. */
-
-template<typename T, size_t Bytes>
-bool operator== (T lhs, const std::atomic<packed<T, Bytes>> &rhs)
-{
- return lhs == rhs.load ();
-}
-
-template<typename T, size_t Bytes>
-bool operator== (const std::atomic<packed<T, Bytes>> &lhs, T rhs)
-{
- return lhs.load () == rhs;
-}
+/* Add some comparisons between std::atomic<packed<T>> and packed<T>
+ and T. We need this because even though std::atomic<T> doesn't
+ define these operators, the relational expressions still work via
+ implicit conversions. Those wouldn't work when wrapped in packed
+ without these operators, because they'd require two implicit
+ conversions to go from T to packed<T> to std::atomic<packed<T>>
+ (and back), and C++ only does one. */
+
+#define PACKED_ATOMIC_OP(OP) \
+ template<typename T, size_t Bytes> \
+ bool operator OP (const std::atomic<packed<T, Bytes>> &lhs, \
+ const std::atomic<packed<T, Bytes>> &rhs) \
+ { \
+ return lhs.load () OP rhs.load (); \
+ } \
+ \
+ template<typename T, size_t Bytes> \
+ bool operator OP (T lhs, const std::atomic<packed<T, Bytes>> &rhs) \
+ { \
+ return lhs OP rhs.load (); \
+ } \
+ \
+ template<typename T, size_t Bytes> \
+ bool operator OP (const std::atomic<packed<T, Bytes>> &lhs, T rhs) \
+ { \
+ return lhs.load () OP rhs; \
+ } \
+ \
+ template<typename T, size_t Bytes> \
+ bool operator OP (const std::atomic<packed<T, Bytes>> &lhs, \
+ packed<T, Bytes> rhs) \
+ { \
+ return lhs.load () OP rhs; \
+ } \
+ \
+ template<typename T, size_t Bytes> \
+ bool operator OP (packed<T, Bytes> lhs, \
+ const std::atomic<packed<T, Bytes>> &rhs) \
+ { \
+ return lhs OP rhs.load (); \
+ }

-template<typename T, size_t Bytes>
-bool operator!= (T lhs, const std::atomic<packed<T, Bytes>> &rhs)
-{
- return !(lhs == rhs);
-}
+PACKED_ATOMIC_OP (==)
+PACKED_ATOMIC_OP (!=)
+PACKED_ATOMIC_OP (>)
+PACKED_ATOMIC_OP (<)
+PACKED_ATOMIC_OP (>=)
+PACKED_ATOMIC_OP (<=)

-template<typename T, size_t Bytes>
-bool operator!= (const std::atomic<packed<T, Bytes>> &lhs, T rhs)
-{
- return !(lhs == rhs);
-}
+#undef PACKED_ATOMIC_OP

#endif
--
2.36.0