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Re: [PATCH] support: Add TEST_COMPARE macro
- From: Florian Weimer <fweimer at redhat dot com>
- To: Paul Eggert <eggert at cs dot ucla dot edu>, Siddhesh Poyarekar <siddhesh at gotplt dot org>, GNU C Library <libc-alpha at sourceware dot org>
- Cc: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Date: Fri, 1 Dec 2017 16:53:11 +0100
- Subject: Re: [PATCH] support: Add TEST_COMPARE macro
- Authentication-results: sourceware.org; auth=none
- References: <8d63a2dc-f9e9-acaa-5ac5-ac5c4fbd6c9f@redhat.com> <8c399cde-3093-0195-a89a-ca230540cffb@gotplt.org> <8339a519-935a-019c-4a8f-798e37f6f346@redhat.com> <5c5fbfc4-0077-22ad-1fd4-53388acaf1e7@cs.ucla.edu> <c51c9a5a-29f2-6461-3a53-f91868b222ca@redhat.com> <96692ad0-180c-6e7c-79c8-e5c96d79e34c@cs.ucla.edu> <7e965c74-8113-72b9-276c-baa031df007e@redhat.com> <24bc9987-5af7-6e8a-9b3d-aeae4a45f60a@cs.ucla.edu> <aa669215-dd46-18c8-07bb-94a67092fc73@redhat.com> <72d1c0c0-44b3-69f7-7630-0d47be285a30@cs.ucla.edu> <f0593826-1721-d424-905c-6755b813bbf7@redhat.com> <2b76ec51-8dac-2fc9-ba32-512fdfbec2ff@cs.ucla.edu> <17e4d3db-8a69-e50c-07b1-71e1e8739d9d@redhat.com> <742d0fab-b17e-a7f5-62df-d87510454aa4@cs.ucla.edu>
On 11/27/2017 07:53 PM, Paul Eggert wrote:
On 11/27/2017 10:43 AM, Florian Weimer wrote:
I don't understand.
It is perfectly reasonable to warn for
ch == EOF
(with ch of type char)
Sure, but that's a different topic. I was writing about the topic at
hand, which is that C integer comparison sometimes disagrees with
mathematical comparison. When ch is of type char, (ch == EOF) always
returns the mathematically-correct answer on glibc platforms. None of
the proposed TEST_COMPARE patches would catch the char-vs-EOF problem,
because they're not designed to catch it: they're designed to catch the
C-vs-mathematical comparison problem.
Yeah, we got side-tracked.
I incorporated your suggestion about rejecting sign-altering promotions
into the attached patch. It also prints hexadecimal values with the
appropriate (type-dependent) width.
Thanks,
Florian
Subject: [PATCH] support: Add TEST_COMPARE macro
To: libc-alpha@sourceware.org
2017-12-01 Florian Weimer <fweimer@redhat.com>
* support/check.h (TEST_COMPARE): Define.
(support_test_compare_failure): Declare.
* support/Makefile (libsupport-routines): Add
support_test_compare_failure.
(tests): Add tst-test_compare.
* support /support_test_compare_failure.c: New file.
* support/tst-test_compare.c: Likewise.
diff --git a/support/Makefile b/support/Makefile
index 384fecb65a..bb81825fc2 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -54,6 +54,7 @@ libsupport-routines = \
support_record_failure \
support_run_diff \
support_shared_allocate \
+ support_test_compare_failure \
support_write_file_string \
support_test_main \
support_test_verify_impl \
@@ -143,6 +144,7 @@ tests = \
tst-support_capture_subprocess \
tst-support_format_dns_packet \
tst-support_record_failure \
+ tst-test_compare \
tst-xreadlink \
ifeq ($(run-built-tests),yes)
diff --git a/support/check.h b/support/check.h
index bdcd12952a..57adf84579 100644
--- a/support/check.h
+++ b/support/check.h
@@ -86,6 +86,64 @@ void support_test_verify_exit_impl (int status, const char *file, int line,
does not support reporting failures from a DSO. */
void support_record_failure (void);
+/* Compare the two integers LEFT and RIGHT and report failure if they
+ are different. */
+#define TEST_COMPARE(left, right) \
+ ({ \
+ typedef __typeof__ (left) __left_type; \
+ typedef __typeof__ (right) __right_type; \
+ __left_type __left_value = (left); \
+ __right_type __right_value = (right); \
+ /* Prevent use with floating-point and boolean types. */ \
+ _Static_assert ((__left_type) 0.1 == (__left_type) 0, \
+ "left value has floating-point type"); \
+ _Static_assert ((__right_type) 0.1 == (__right_type) 0, \
+ "right value has floating-point type"); \
+ /* Prevent accidental use with larger-than-long long types. */ \
+ _Static_assert (sizeof (__left_value) <= sizeof (long long), \
+ "left value fits into long long"); \
+ _Static_assert (sizeof (__right_value) <= sizeof (long long), \
+ "right value fits into long long"); \
+ /* Make sure that type promotion does not alter the sign. */ \
+ enum \
+ { \
+ __left_is_unsigned = (__left_type) -1 > 0, \
+ __right_is_unsigned = (__right_type) -1 > 0, \
+ __left_promotes_to_right = __left_is_unsigned \
+ && sizeof (__left_value) < sizeof (__right_value), \
+ __right_promotes_to_left = __right_is_unsigned \
+ && sizeof (__right_value) < sizeof (__left_value) \
+ }; \
+ _Static_assert (__left_is_unsigned == __right_is_unsigned \
+ || __left_promotes_to_right \
+ || __right_promotes_to_left, \
+ "integer promotion may alter sign of operands"); \
+ /* Compare the value. */ \
+ if (__left_value != __right_value) \
+ /* Pass the sign for printing the correct value. */ \
+ support_test_compare_failure \
+ (__FILE__, __LINE__, \
+ #left, __left_value, __left_value < 0, sizeof (__left_type), \
+ #right, __right_value, __right_value < 0, sizeof (__right_type)); \
+ })
+
+/* Internal implementation of TEST_COMPARE. LEFT_NEGATIVE and
+ RIGHT_NEGATIVE are used to store the sign separately, so that both
+ unsigned long long and long long arguments fit into LEFT_VALUE and
+ RIGHT_VALUE, and the function can still print the original value.
+ LEFT_SIZE and RIGHT_SIZE specify the size of the argument in bytes,
+ for hexadecimal formatting. */
+void support_test_compare_failure (const char *file, int line,
+ const char *left_expr,
+ long long left_value,
+ int left_negative,
+ int left_size,
+ const char *right_expr,
+ long long right_value,
+ int right_negative,
+ int right_size);
+
+
/* Internal function called by the test driver. */
int support_report_failure (int status)
__attribute__ ((weak, warn_unused_result));
diff --git a/support/support_test_compare_failure.c b/support/support_test_compare_failure.c
new file mode 100644
index 0000000000..ab55b9f51a
--- /dev/null
+++ b/support/support_test_compare_failure.c
@@ -0,0 +1,51 @@
+/* Reporting a numeric comparison failure.
+ Copyright (C) 2017 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <stdio.h>
+#include <support/check.h>
+
+static void
+report (const char *which, const char *expr, long long value, int negative,
+ int size)
+{
+ printf (" %s: ", which);
+ if (negative)
+ printf ("%lld", value);
+ else
+ printf ("%llu", (unsigned long long) value);
+ unsigned long long mask
+ = (~0ULL) >> (8 * (sizeof (unsigned long long) - size));
+ printf (" (0x%llx); from: %s\n", (unsigned long long) value & mask, expr);
+}
+
+void
+support_test_compare_failure (const char *file, int line,
+ const char *left_expr,
+ long long left_value,
+ int left_negative,
+ int left_size,
+ const char *right_expr,
+ long long right_value,
+ int right_negative,
+ int right_size)
+{
+ support_record_failure ();
+ printf ("%s:%d: numeric comparison failure\n", file, line);
+ report (" left", left_expr, left_value, left_negative, left_size);
+ report ("right", right_expr, right_value, right_negative, right_size);
+}
diff --git a/support/tst-test_compare.c b/support/tst-test_compare.c
new file mode 100644
index 0000000000..2356e800dc
--- /dev/null
+++ b/support/tst-test_compare.c
@@ -0,0 +1,68 @@
+/* Basic test for the TEST_COMPARE macro.
+ Copyright (C) 2017 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <string.h>
+#include <support/check.h>
+#include <support/capture_subprocess.h>
+
+static void
+subprocess (void *closure)
+{
+ char ch = 1;
+ /* These tests should fail. */
+ TEST_COMPARE (ch, -1); /* Line 28. */
+ TEST_COMPARE (2LL, -2LL); /* Line 29. */
+ TEST_COMPARE (3L, (short) -3); /* Line 30. */
+}
+
+static int
+do_test (void)
+{
+ /* This should succeed. */
+ TEST_COMPARE (1, 1);
+ TEST_COMPARE (2LL, 2U);
+
+ struct support_capture_subprocess proc = support_capture_subprocess
+ (&subprocess, NULL);
+
+ /* Discard the reported error. */
+ support_record_failure_reset ();
+
+ puts ("info: *** subprocess output starts ***");
+ fputs (proc.out.buffer, stdout);
+ puts ("info: *** subprocess output ends ***");
+
+ TEST_VERIFY
+ (strcmp (proc.out.buffer,
+ "tst-test_compare.c:28: numeric comparison failure\n"
+ " left: 1 (0x1); from: ch\n"
+ " right: -1 (0xffffffff); from: -1\n"
+ "tst-test_compare.c:29: numeric comparison failure\n"
+ " left: 2 (0x2); from: 2LL\n"
+ " right: -2 (0xfffffffffffffffe); from: -2LL\n"
+ "tst-test_compare.c:30: numeric comparison failure\n"
+ " left: 3 (0x3); from: 3L\n"
+ " right: -3 (0xfffd); from: (short) -3\n") == 0);
+
+ /* Check that there is no output on standard error. */
+ support_capture_subprocess_check (&proc, "TEST_COMPARE", 0, sc_allow_stdout);
+
+ return 0;
+}
+
+#include <support/test-driver.c>