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Re: Fix p_secstodate overflow handling (bug 22463)
- From: Paul Eggert <eggert at cs dot ucla dot edu>
- To: Joseph Myers <joseph at codesourcery dot com>, libc-alpha at sourceware dot org
- Date: Mon, 20 Nov 2017 21:15:58 -0800
- Subject: Re: Fix p_secstodate overflow handling (bug 22463)
- Authentication-results: sourceware.org; auth=none
- References: <alpine.DEB.2.20.1711210128340.12922@digraph.polyomino.org.uk>
Joseph Myers wrote:
If __gmtime_r returns NULL (because the year overflows the range of
int), this will dereference a null pointer.
'clock' must be in the range 0 .. 2**32-1, so the year cannot overflow the range
of int. This range is enforced by all callers of p_secstodate, and is required
by Internet RFC 4034 section 3.2.
With current GCC
mainline, there is a compilation failure because of the possible
buffer overrun.
That's a false alarm since the buffer cannot overrun. In Gnulib I work around
such alarms by using the 'assume' macro defined by verify.h. Or one can use
__builtin_unreachable () directly, as is done in the attached patch. (The
'assume' macro is more readable, but is one more thing to add....)
I couldn't find a specification for how this function is meant to
behave. This patch makes the overflow cases use <overflow> as the
output string
The RFC says that if gmtime_r fails, one can just output the time_t value as an
unsigned decimal integer.
Although all the GCC diagnostics for p_secstodate are false alarms, there is a
bug here that GCC does not report: on platforms with 32-bit signed time_t, the
code mishandles timestamps after 2038. Proposed patches attached. Although I
haven't tested them, the first patch just adds a Gnulib include file that is
well-tested so it should be OK.
The second patch fixes the abovementioned bug. Also, to pacify GCC it uses a
call to __builtin_unreachable; we could simply make the static buffer larger, or
use snprintf, but I hate surrendering to false alarms.
If you'd rather not add intprops.h to glibc, the TIME_T_MAX macros from
elsewhere in glibc could be duped here. However, I think it's time to
incorporate intprops.h, as glibc is running into several overflow-related
problems for which intprops.h has well-tested solutions.
From 68385e2d409a919a1299cf8f2ae046f5f38e0d6c Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 20 Nov 2017 20:56:06 -0800
Subject: [PATCH 1/2] New internal include file <intprops.h>
* include/intprops.h: New file, taken from Gnulib.
---
ChangeLog | 3 +
include/intprops.h | 453 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 456 insertions(+)
create mode 100644 include/intprops.h
diff --git a/ChangeLog b/ChangeLog
index 50da3df..eece2d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
2017-11-20 Paul Eggert <eggert@cs.ucla.edu>
+ New internal include file <intprops.h>
+ * include/intprops.h: New file, taken from Gnulib.
+
regex: don't assume uint64_t or uint32_t
This avoids -Werror=overflow errors for 32-bit systems in
the 64-bit case. Problem reported by Joseph Myers in:
diff --git a/include/intprops.h b/include/intprops.h
new file mode 100644
index 0000000..fd6d926
--- /dev/null
+++ b/include/intprops.h
@@ -0,0 +1,453 @@
+/* intprops.h -- properties of integer types
+
+ Copyright (C) 2001-2017 Free Software Foundation, Inc.
+
+ This program 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.
+
+ 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Paul Eggert. */
+
+#ifndef _GL_INTPROPS_H
+#define _GL_INTPROPS_H
+
+#include <limits.h>
+
+/* Return a value with the common real type of E and V and the value of V. */
+#define _GL_INT_CONVERT(e, v) (0 * (e) + (v))
+
+/* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see
+ <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */
+#define _GL_INT_NEGATE_CONVERT(e, v) (0 * (e) - (v))
+
+/* The extra casts in the following macros work around compiler bugs,
+ e.g., in Cray C 5.0.3.0. */
+
+/* True if the arithmetic type T is an integer type. bool counts as
+ an integer. */
+#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
+
+/* True if the real type T is signed. */
+#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
+
+/* Return 1 if the real expression E, after promotion, has a
+ signed or floating type. */
+#define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
+
+
+/* Minimum and maximum values for integer types and expressions. */
+
+/* The width in bits of the integer type or expression T.
+ Padding bits are not supported; this is checked at compile-time below. */
+#define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT)
+
+/* The maximum and minimum values for the integer type T. */
+#define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t))
+#define TYPE_MAXIMUM(t) \
+ ((t) (! TYPE_SIGNED (t) \
+ ? (t) -1 \
+ : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1)))
+
+/* The maximum and minimum values for the type of the expression E,
+ after integer promotion. E should not have side effects. */
+#define _GL_INT_MINIMUM(e) \
+ (EXPR_SIGNED (e) \
+ ? ~ _GL_SIGNED_INT_MAXIMUM (e) \
+ : _GL_INT_CONVERT (e, 0))
+#define _GL_INT_MAXIMUM(e) \
+ (EXPR_SIGNED (e) \
+ ? _GL_SIGNED_INT_MAXIMUM (e) \
+ : _GL_INT_NEGATE_CONVERT (e, 1))
+#define _GL_SIGNED_INT_MAXIMUM(e) \
+ (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH ((e) + 0) - 2)) - 1) * 2 + 1)
+
+/* Work around OpenVMS incompatibility with C99. */
+#if !defined LLONG_MAX && defined __INT64_MAX
+# define LLONG_MAX __INT64_MAX
+# define LLONG_MIN __INT64_MIN
+#endif
+
+/* This include file assumes that signed types are two's complement without
+ padding bits; the above macros have undefined behavior otherwise.
+ If this is a problem for you, please let us know how to fix it for your host.
+ This assumption is tested by the intprops-tests module. */
+
+/* Does the __typeof__ keyword work? This could be done by
+ 'configure', but for now it's easier to do it by hand. */
+#if (2 <= __GNUC__ \
+ || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \
+ || (0x5110 <= __SUNPRO_C && !__STDC__))
+# define _GL_HAVE___TYPEOF__ 1
+#else
+# define _GL_HAVE___TYPEOF__ 0
+#endif
+
+/* Return 1 if the integer type or expression T might be signed. Return 0
+ if it is definitely unsigned. This macro does not evaluate its argument,
+ and expands to an integer constant expression. */
+#if _GL_HAVE___TYPEOF__
+# define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t))
+#else
+# define _GL_SIGNED_TYPE_OR_EXPR(t) 1
+#endif
+
+/* Bound on length of the string representing an unsigned integer
+ value representable in B bits. log10 (2.0) < 146/485. The
+ smallest value of B where this bound is not tight is 2621. */
+#define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485)
+
+/* Bound on length of the string representing an integer type or expression T.
+ Subtract 1 for the sign bit if T is signed, and then add 1 more for
+ a minus sign if needed.
+
+ Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is
+ signed, this macro may overestimate the true bound by one byte when
+ applied to unsigned types of size 2, 4, 16, ... bytes. */
+#define INT_STRLEN_BOUND(t) \
+ (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \
+ + _GL_SIGNED_TYPE_OR_EXPR (t))
+
+/* Bound on buffer size needed to represent an integer type or expression T,
+ including the terminating null. */
+#define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
+
+
+/* Range overflow checks.
+
+ The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C
+ operators might not yield numerically correct answers due to
+ arithmetic overflow. They do not rely on undefined or
+ implementation-defined behavior. Their implementations are simple
+ and straightforward, but they are a bit harder to use than the
+ INT_<op>_OVERFLOW macros described below.
+
+ Example usage:
+
+ long int i = ...;
+ long int j = ...;
+ if (INT_MULTIPLY_RANGE_OVERFLOW (i, j, LONG_MIN, LONG_MAX))
+ printf ("multiply would overflow");
+ else
+ printf ("product is %ld", i * j);
+
+ Restrictions on *_RANGE_OVERFLOW macros:
+
+ These macros do not check for all possible numerical problems or
+ undefined or unspecified behavior: they do not check for division
+ by zero, for bad shift counts, or for shifting negative numbers.
+
+ These macros may evaluate their arguments zero or multiple times,
+ so the arguments should not have side effects. The arithmetic
+ arguments (including the MIN and MAX arguments) must be of the same
+ integer type after the usual arithmetic conversions, and the type
+ must have minimum value MIN and maximum MAX. Unsigned types should
+ use a zero MIN of the proper type.
+
+ These macros are tuned for constant MIN and MAX. For commutative
+ operations such as A + B, they are also tuned for constant B. */
+
+/* Return 1 if A + B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. */
+#define INT_ADD_RANGE_OVERFLOW(a, b, min, max) \
+ ((b) < 0 \
+ ? (a) < (min) - (b) \
+ : (max) - (b) < (a))
+
+/* Return 1 if A - B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. */
+#define INT_SUBTRACT_RANGE_OVERFLOW(a, b, min, max) \
+ ((b) < 0 \
+ ? (max) + (b) < (a) \
+ : (a) < (min) + (b))
+
+/* Return 1 if - A would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. */
+#define INT_NEGATE_RANGE_OVERFLOW(a, min, max) \
+ ((min) < 0 \
+ ? (a) < - (max) \
+ : 0 < (a))
+
+/* Return 1 if A * B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. Avoid && and || as they tickle
+ bugs in Sun C 5.11 2010/08/13 and other compilers; see
+ <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00401.html>. */
+#define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \
+ ((b) < 0 \
+ ? ((a) < 0 \
+ ? (a) < (max) / (b) \
+ : (b) == -1 \
+ ? 0 \
+ : (min) / (b) < (a)) \
+ : (b) == 0 \
+ ? 0 \
+ : ((a) < 0 \
+ ? (a) < (min) / (b) \
+ : (max) / (b) < (a)))
+
+/* Return 1 if A / B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. Do not check for division by zero. */
+#define INT_DIVIDE_RANGE_OVERFLOW(a, b, min, max) \
+ ((min) < 0 && (b) == -1 && (a) < - (max))
+
+/* Return 1 if A % B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. Do not check for division by zero.
+ Mathematically, % should never overflow, but on x86-like hosts
+ INT_MIN % -1 traps, and the C standard permits this, so treat this
+ as an overflow too. */
+#define INT_REMAINDER_RANGE_OVERFLOW(a, b, min, max) \
+ INT_DIVIDE_RANGE_OVERFLOW (a, b, min, max)
+
+/* Return 1 if A << B would overflow in [MIN,MAX] arithmetic.
+ See above for restrictions. Here, MIN and MAX are for A only, and B need
+ not be of the same type as the other arguments. The C standard says that
+ behavior is undefined for shifts unless 0 <= B < wordwidth, and that when
+ A is negative then A << B has undefined behavior and A >> B has
+ implementation-defined behavior, but do not check these other
+ restrictions. */
+#define INT_LEFT_SHIFT_RANGE_OVERFLOW(a, b, min, max) \
+ ((a) < 0 \
+ ? (a) < (min) >> (b) \
+ : (max) >> (b) < (a))
+
+/* True if __builtin_add_overflow (A, B, P) works when P is non-null. */
+#if 5 <= __GNUC__ && !defined __ICC
+# define _GL_HAS_BUILTIN_OVERFLOW 1
+#else
+# define _GL_HAS_BUILTIN_OVERFLOW 0
+#endif
+
+/* True if __builtin_add_overflow_p (A, B, C) works. */
+#define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
+
+/* The _GL*_OVERFLOW macros have the same restrictions as the
+ *_RANGE_OVERFLOW macros, except that they do not assume that operands
+ (e.g., A and B) have the same type as MIN and MAX. Instead, they assume
+ that the result (e.g., A + B) has that type. */
+#if _GL_HAS_BUILTIN_OVERFLOW_P
+# define _GL_ADD_OVERFLOW(a, b, min, max) \
+ __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0)
+# define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
+ __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)
+# define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
+ __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0)
+#else
+# define _GL_ADD_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \
+ : (a) < 0 ? (b) <= (a) + (b) \
+ : (b) < 0 ? (a) <= (a) + (b) \
+ : (a) + (b) < (b))
+# define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \
+ : (a) < 0 ? 1 \
+ : (b) < 0 ? (a) - (b) <= (a) \
+ : (a) < (b))
+# define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
+ (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \
+ || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max))
+#endif
+#define _GL_DIVIDE_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \
+ : (a) < 0 ? (b) <= (a) + (b) - 1 \
+ : (b) < 0 && (a) + (b) <= (a))
+#define _GL_REMAINDER_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \
+ : (a) < 0 ? (a) % (b) != ((max) - (b) + 1) % (b) \
+ : (b) < 0 && ! _GL_UNSIGNED_NEG_MULTIPLE (a, b, max))
+
+/* Return a nonzero value if A is a mathematical multiple of B, where
+ A is unsigned, B is negative, and MAX is the maximum value of A's
+ type. A's type must be the same as (A % B)'s type. Normally (A %
+ -B == 0) suffices, but things get tricky if -B would overflow. */
+#define _GL_UNSIGNED_NEG_MULTIPLE(a, b, max) \
+ (((b) < -_GL_SIGNED_INT_MAXIMUM (b) \
+ ? (_GL_SIGNED_INT_MAXIMUM (b) == (max) \
+ ? (a) \
+ : (a) % (_GL_INT_CONVERT (a, _GL_SIGNED_INT_MAXIMUM (b)) + 1)) \
+ : (a) % - (b)) \
+ == 0)
+
+/* Check for integer overflow, and report low order bits of answer.
+
+ The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators
+ might not yield numerically correct answers due to arithmetic overflow.
+ The INT_<op>_WRAPV macros also store the low-order bits of the answer.
+ These macros work correctly on all known practical hosts, and do not rely
+ on undefined behavior due to signed arithmetic overflow.
+
+ Example usage, assuming A and B are long int:
+
+ if (INT_MULTIPLY_OVERFLOW (a, b))
+ printf ("result would overflow\n");
+ else
+ printf ("result is %ld (no overflow)\n", a * b);
+
+ Example usage with WRAPV flavor:
+
+ long int result;
+ bool overflow = INT_MULTIPLY_WRAPV (a, b, &result);
+ printf ("result is %ld (%s)\n", result,
+ overflow ? "after overflow" : "no overflow");
+
+ Restrictions on these macros:
+
+ These macros do not check for all possible numerical problems or
+ undefined or unspecified behavior: they do not check for division
+ by zero, for bad shift counts, or for shifting negative numbers.
+
+ These macros may evaluate their arguments zero or multiple times, so the
+ arguments should not have side effects.
+
+ The WRAPV macros are not constant expressions. They support only
+ +, binary -, and *. The result type must be signed.
+
+ These macros are tuned for their last argument being a constant.
+
+ Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B,
+ A % B, and A << B would overflow, respectively. */
+
+#define INT_ADD_OVERFLOW(a, b) \
+ _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW)
+#define INT_SUBTRACT_OVERFLOW(a, b) \
+ _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW)
+#if _GL_HAS_BUILTIN_OVERFLOW_P
+# define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a)
+#else
+# define INT_NEGATE_OVERFLOW(a) \
+ INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
+#endif
+#define INT_MULTIPLY_OVERFLOW(a, b) \
+ _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW)
+#define INT_DIVIDE_OVERFLOW(a, b) \
+ _GL_BINARY_OP_OVERFLOW (a, b, _GL_DIVIDE_OVERFLOW)
+#define INT_REMAINDER_OVERFLOW(a, b) \
+ _GL_BINARY_OP_OVERFLOW (a, b, _GL_REMAINDER_OVERFLOW)
+#define INT_LEFT_SHIFT_OVERFLOW(a, b) \
+ INT_LEFT_SHIFT_RANGE_OVERFLOW (a, b, \
+ _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
+
+/* Return 1 if the expression A <op> B would overflow,
+ where OP_RESULT_OVERFLOW (A, B, MIN, MAX) does the actual test,
+ assuming MIN and MAX are the minimum and maximum for the result type.
+ Arguments should be free of side effects. */
+#define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \
+ op_result_overflow (a, b, \
+ _GL_INT_MINIMUM (0 * (b) + (a)), \
+ _GL_INT_MAXIMUM (0 * (b) + (a)))
+
+/* Store the low-order bits of A + B, A - B, A * B, respectively, into *R.
+ Return 1 if the result overflows. See above for restrictions. */
+#define INT_ADD_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, INT_ADD_OVERFLOW)
+#define INT_SUBTRACT_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, INT_SUBTRACT_OVERFLOW)
+#define INT_MULTIPLY_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW)
+
+/* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See:
+ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193
+ https://llvm.org/bugs/show_bug.cgi?id=25390
+ For now, assume all versions of GCC-like compilers generate bogus
+ warnings for _Generic. This matters only for older compilers that
+ lack __builtin_add_overflow. */
+#if __GNUC__
+# define _GL__GENERIC_BOGUS 1
+#else
+# define _GL__GENERIC_BOGUS 0
+#endif
+
+/* Store the low-order bits of A <op> B into *R, where OP specifies
+ the operation. BUILTIN is the builtin operation, and OVERFLOW the
+ overflow predicate. Return 1 if the result overflows. See above
+ for restrictions. */
+#if _GL_HAS_BUILTIN_OVERFLOW
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r)
+#elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+ (_Generic \
+ (*(r), \
+ signed char: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ signed char, SCHAR_MIN, SCHAR_MAX), \
+ short int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ short int, SHRT_MIN, SHRT_MAX), \
+ int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ int, INT_MIN, INT_MAX), \
+ long int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX), \
+ long long int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
+ long long int, LLONG_MIN, LLONG_MAX)))
+#else
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+ (sizeof *(r) == sizeof (signed char) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ signed char, SCHAR_MIN, SCHAR_MAX) \
+ : sizeof *(r) == sizeof (short int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ short int, SHRT_MIN, SHRT_MAX) \
+ : sizeof *(r) == sizeof (int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ int, INT_MIN, INT_MAX) \
+ : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
+# ifdef LLONG_MAX
+# define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
+ (sizeof *(r) == sizeof (long int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX) \
+ : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
+ long long int, LLONG_MIN, LLONG_MAX))
+# else
+# define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX)
+# endif
+#endif
+
+/* Store the low-order bits of A <op> B into *R, where the operation
+ is given by OP. Use the unsigned type UT for calculation to avoid
+ overflow problems. *R's type is T, with extrema TMIN and TMAX.
+ T must be a signed integer type. Return 1 if the result overflows. */
+#define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \
+ (sizeof ((a) op (b)) < sizeof (t) \
+ ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \
+ : _GL_INT_OP_CALC1 (a, b, r, op, overflow, ut, t, tmin, tmax))
+#define _GL_INT_OP_CALC1(a, b, r, op, overflow, ut, t, tmin, tmax) \
+ ((overflow (a, b) \
+ || (EXPR_SIGNED ((a) op (b)) && ((a) op (b)) < (tmin)) \
+ || (tmax) < ((a) op (b))) \
+ ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 1) \
+ : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 0))
+
+/* Return the low-order bits of A <op> B, where the operation is given
+ by OP. Use the unsigned type UT for calculation to avoid undefined
+ behavior on signed integer overflow, and convert the result to type T.
+ UT is at least as wide as T and is no narrower than unsigned int,
+ T is two's complement, and there is no padding or trap representations.
+ Assume that converting UT to T yields the low-order bits, as is
+ done in all known two's-complement C compilers. E.g., see:
+ https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html
+
+ According to the C standard, converting UT to T yields an
+ implementation-defined result or signal for values outside T's
+ range. However, code that works around this theoretical problem
+ runs afoul of a compiler bug in Oracle Studio 12.3 x86. See:
+ https://lists.gnu.org/r/bug-gnulib/2017-04/msg00049.html
+ As the compiler bug is real, don't try to work around the
+ theoretical problem. */
+
+#define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t) \
+ ((t) ((ut) (a) op (ut) (b)))
+
+#endif /* _GL_INTPROPS_H */
--
2.7.4
From fa6f9fb3fd4d9faeaf83d80c31b7d8891e9410b7 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 20 Nov 2017 20:58:44 -0800
Subject: [PATCH 2/2] [BZ #22463]
* resolv/res_debug.c: Include <intprops.h>.
(libresolv_hidden_def): If the timestamp is out of time_t range,
just generate an unsigned decimal integer.
Use strftime instead of sprintf to format timestamps.
Use __builtin_unreachable to pacify GCC.
---
ChangeLog | 7 +++++++
resolv/res_debug.c | 32 +++++++++++++++++++++++---------
2 files changed, 30 insertions(+), 9 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index eece2d8..e47525d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
2017-11-20 Paul Eggert <eggert@cs.ucla.edu>
+ [BZ #22463]
+ * resolv/res_debug.c: Include <intprops.h>.
+ (libresolv_hidden_def): If the timestamp is out of time_t range,
+ just generate an unsigned decimal integer.
+ Use strftime instead of sprintf to format timestamps.
+ Use __builtin_unreachable to pacify GCC.
+
New internal include file <intprops.h>
* include/intprops.h: New file, taken from Gnulib.
diff --git a/resolv/res_debug.c b/resolv/res_debug.c
index 4114c2d..01285b7 100644
--- a/resolv/res_debug.c
+++ b/resolv/res_debug.c
@@ -99,6 +99,7 @@
#include <ctype.h>
#include <errno.h>
+#include <intprops.h>
#include <math.h>
#include <netdb.h>
#include <resolv/resolv-internal.h>
@@ -1052,23 +1053,36 @@ libresolv_hidden_def (__dn_count_labels)
/*
- * Make dates expressed in seconds-since-Jan-1-1970 easy to read.
+ * Convert SECS, a count of seconds since 1970-01-01, to string format.
+ * SECS must be less than 2**32.
* SIG records are required to be printed like this, by the Secure DNS RFC.
*/
char *
p_secstodate (u_long secs) {
/* XXX nonreentrant */
- static char output[15]; /* YYYYMMDDHHMMSS and null */
- time_t clock = secs;
+
+ /* A null-terminated string containing either YYYYMMDDHHMMSS
+ or an unsigned decimal integer with at most 10 digits.
+ See Internet RFC 4034 section 3.2. */
+ static char output[sizeof "YYYYMMDDHHMMSS"];
+
struct tm *time;
struct tm timebuf;
- time = __gmtime_r(&clock, &timebuf);
- time->tm_year += 1900;
- time->tm_mon += 1;
- sprintf(output, "%04d%02d%02d%02d%02d%02d",
- time->tm_year, time->tm_mon, time->tm_mday,
- time->tm_hour, time->tm_min, time->tm_sec);
+
+ if (secs <= TYPE_MAXIMUM (time_t)) {
+ time_t clock = secs;
+ time = __gmtime_r (&clock, &timebuf);
+ } else if (secs <= 0xffffffff)
+ time = NULL;
+ else
+ __builtin_unreachable ();
+
+ if (time == NULL)
+ sprintf (output, "%lu", secs);
+ else
+ strftime (output, sizeof output, "%Y%M%D%H%M%S", &timebuf);
+
return (output);
}
libresolv_hidden_def (__p_secstodate)
--
2.7.4