Jim Meyering wrote:
Good catch.
Thanks.
In trying it out on GNU Emacs with GCC 6.2 I ran into another problem: it
complains at compile-time if __builtin_add_overflow's 3rd arg is null. In some
GCC versions this is supposed to discard the value, but I guess that capability
is superseded by __builtin_add_overflow_p. So I installed the attached
additional patch, which avoids the need for a null argument so we don't have to
worry about GCC version details there.
From 77de583eb1a7577a0e85cd4023655d5ee542a205 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 29 Aug 2016 12:03:51 -0700
Subject: [PATCH] intprops.h: port recent changes to GCC 6.2.0
* lib/intprops.h (__has_builtin): Move earlier.
(_GL_HAS_BUILTIN_OVERFLOW): Rename from
_GL_HAS_BUILTIN_OVERFLOW_WITH_NULL and don't worry about whether
the last argument can be null. All uses changed.
(_GL_HAS_BUILTIN_OVERFLOW_P): Also test __has_builtin.
(_GL_ADD_OVERFLOW, _GL_SUBTRACT_OVERFLOW, _GL_MULTIPLY_OVERFLOW):
Don't try to use 3rd arg null, as this doesn't work on GCC 6.2.0
and it's not clear which GCC versions it works for.
(_GL_INT_OP_WRAPV): Use _GL_HAS_BUILTIN_OVERFLOW instead of
its definiens.
---
ChangeLog | 12 ++++++++++++
lib/intprops.h | 27 +++++++++++----------------
2 files changed, 23 insertions(+), 16 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 70012b7..cc437f5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
2016-08-29 Paul Eggert <egg...@cs.ucla.edu>
+ intprops.h: port recent changes to GCC 6.2.0
+ * lib/intprops.h (__has_builtin): Move earlier.
+ (_GL_HAS_BUILTIN_OVERFLOW): Rename from
+ _GL_HAS_BUILTIN_OVERFLOW_WITH_NULL and don't worry about whether
+ the last argument can be null. All uses changed.
+ (_GL_HAS_BUILTIN_OVERFLOW_P): Also test __has_builtin.
+ (_GL_ADD_OVERFLOW, _GL_SUBTRACT_OVERFLOW, _GL_MULTIPLY_OVERFLOW):
+ Don't try to use 3rd arg null, as this doesn't work on GCC 6.2.0
+ and it's not clear which GCC versions it works for.
+ (_GL_INT_OP_WRAPV): Use _GL_HAS_BUILTIN_OVERFLOW instead of
+ its definiens.
+
intprops.h: use __typeof__ with GCC 7
* lib/intprops.h (_GL_ADD_OVERFLOW, _GL_SUBTRACT_OVERFLOW)
(_GL_MULTIPLY_OVERFLOW): Use __typeof__ as in the GCC manual.
diff --git a/lib/intprops.h b/lib/intprops.h
index 32ee71a..744e64b 100644
--- a/lib/intprops.h
+++ b/lib/intprops.h
@@ -23,6 +23,10 @@
#include <limits.h>
#include <verify.h>
+#ifndef __has_builtin
+# define __has_builtin(x) 0
+#endif
+
/* 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))
@@ -228,11 +232,13 @@ verify (TYPE_MAXIMUM (long long int) == LLONG_MAX);
? (a) < (min) >> (b) \
: (max) >> (b) < (a))
-/* True if __builtin_add_overflow (A, B, P) works when P is null. */
-#define _GL_HAS_BUILTIN_OVERFLOW_WITH_NULL (6 == __GNUC__)
+/* True if __builtin_add_overflow (A, B, P) works when P is non-null. */
+#define _GL_HAS_BUILTIN_OVERFLOW \
+ (5 <= __GNUC__ || __has_builtin (__builtin_add_overflow))
/* True if __builtin_add_overflow_p (A, B, C) works. */
-#define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
+#define _GL_HAS_BUILTIN_OVERFLOW_P \
+ (7 <= __GNUC__ || __has_builtin (__builtin_add_overflow_p))
/* The _GL*_OVERFLOW macros have the same restrictions as the
*_RANGE_OVERFLOW macros, except that they do not assume that operands
@@ -245,13 +251,6 @@ verify (TYPE_MAXIMUM (long long int) == LLONG_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)
-#elif _GL_HAS_BUILTIN_OVERFLOW_WITH_NULL
-# define _GL_ADD_OVERFLOW(a, b, min, max) \
- __builtin_add_overflow (a, b, (__typeof__ ((a) + (b)) *) 0)
-# define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
- __builtin_sub_overflow (a, b, (__typeof__ ((a) - (b)) *) 0)
-# define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
- __builtin_mul_overflow (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) \
@@ -331,7 +330,7 @@ verify (TYPE_MAXIMUM (long long int) == LLONG_MAX);
_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_WITH_NULL
+#if _GL_HAS_BUILTIN_OVERFLOW || _GL_HAS_BUILTIN_OVERFLOW_P
# define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a)
#else
# define INT_NEGATE_OVERFLOW(a) \
@@ -365,10 +364,6 @@ verify (TYPE_MAXIMUM (long long int) == LLONG_MAX);
#define INT_MULTIPLY_WRAPV(a, b, r) \
_GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW)
-#ifndef __has_builtin
-# define __has_builtin(x) 0
-#endif
-
/* 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
@@ -385,7 +380,7 @@ verify (TYPE_MAXIMUM (long long int) == LLONG_MAX);
the operation. BUILTIN is the builtin operation, and OVERFLOW the
overflow predicate. Return 1 if the result overflows. See above
for restrictions. */
-#if 5 <= __GNUC__ || __has_builtin (__builtin_add_overflow)
+#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) \
--
2.7.4
