* bug#50609: number overflow
2021-09-15 19:12 bug#50609: number overflow Stefan Israelsson Tampe
@ 2021-11-04 19:12 ` lloda
2021-11-05 16:35 ` lloda
1 sibling, 0 replies; 3+ messages in thread
From: lloda @ 2021-11-04 19:12 UTC (permalink / raw)
To: 50609
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Not quite comfortable poking around in the compiler, but find a patch attached.
I also found this related bug: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=32644.
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From 699919f181ea94ba00d392b49d07ed85e7535fcc Mon Sep 17 00:00:00 2001
From: Daniel Llorens <lloda@sarc.name>
Date: Thu, 4 Nov 2021 14:52:21 +0100
Subject: [PATCH 1/2] Limit the range of ash, round-ash count argument to INT32
This avoids gmp aborting e.g. with (ash 1 (expt 2 37)). The new limit is
such that (ash 1 (expt 30)) is accepted but (ash 1 (expt 31)) throws.
* libguile/numbers.c (ash, round-ash): As stated.
* test-suite/tests/numbers.test: Test a case known to make gmp abort before.
---
libguile/numbers.c | 98 +++++++++++++++--------------------
test-suite/tests/numbers.test | 5 +-
2 files changed, 47 insertions(+), 56 deletions(-)
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 18bd22dbb..1f7785aa6 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -5090,6 +5090,8 @@ round_right_shift_exact_integer (SCM n, long count)
and moreover that they can be negated without overflow. */
verify (SCM_MOST_NEGATIVE_FIXNUM >= LONG_MIN + 1
&& SCM_MOST_POSITIVE_FIXNUM <= LONG_MAX);
+/* the practicable limits are smaller */
+verify (INT32_MIN >= LONG_MIN && INT32_MAX <= LONG_MAX);
SCM_DEFINE (scm_ash, "ash", 2, 0, 0,
(SCM n, SCM count),
@@ -5110,35 +5112,28 @@ SCM_DEFINE (scm_ash, "ash", 2, 0, 0,
"@end lisp")
#define FUNC_NAME s_scm_ash
{
- if (SCM_I_INUMP (n) || SCM_BIGP (n))
- {
- long bits_to_shift;
-
- if (SCM_I_INUMP (count)) /* fast path, not strictly needed */
- bits_to_shift = SCM_I_INUM (count);
- else if (scm_is_signed_integer (count, LONG_MIN + 1, LONG_MAX))
- /* We exclude LONG_MIN to ensure that 'bits_to_shift' can be
- negated without overflowing. */
- bits_to_shift = scm_to_long (count);
- else if (scm_is_false (scm_positive_p (scm_sum (scm_integer_length (n),
- count))))
- /* Huge right shift that eliminates all but the sign bit */
- return scm_is_false (scm_negative_p (n))
- ? SCM_INUM0 : SCM_I_MAKINUM (-1);
- else if (scm_is_true (scm_zero_p (n)))
- return SCM_INUM0;
- else
- scm_num_overflow ("ash");
-
- if (bits_to_shift > 0)
- return left_shift_exact_integer (n, bits_to_shift);
- else if (SCM_LIKELY (bits_to_shift < 0))
- return floor_right_shift_exact_integer (n, -bits_to_shift);
- else
- return n;
- }
- else
+ if (!SCM_I_INUMP (n) && !SCM_BIGP (n))
SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
+
+ if (scm_is_false (scm_positive_p (scm_sum (scm_integer_length (n),
+ count))))
+ /* Huge right shift that eliminates all but the sign bit */
+ return scm_is_false (scm_negative_p (n))
+ ? SCM_INUM0 : SCM_I_MAKINUM (-1);
+ else if (scm_is_true (scm_zero_p (n)))
+ return SCM_INUM0;
+ else if (scm_is_signed_integer (count, INT32_MIN + 1, INT32_MAX)) {
+ /* We exclude MIN to ensure that 'bits_to_shift' can be
+ negated without overflowing, if INT32_MIN happens to be LONG_MIN */
+ long bits_to_shift = scm_to_long (count);
+ if (bits_to_shift > 0)
+ return left_shift_exact_integer (n, bits_to_shift);
+ else if (SCM_LIKELY (bits_to_shift < 0))
+ return floor_right_shift_exact_integer (n, -bits_to_shift);
+ else
+ return n;
+ } else
+ scm_num_overflow ("ash");
}
#undef FUNC_NAME
@@ -5164,34 +5159,27 @@ SCM_DEFINE (scm_round_ash, "round-ash", 2, 0, 0,
"@end lisp")
#define FUNC_NAME s_scm_round_ash
{
- if (SCM_I_INUMP (n) || SCM_BIGP (n))
- {
- long bits_to_shift;
-
- if (SCM_I_INUMP (count)) /* fast path, not strictly needed */
- bits_to_shift = SCM_I_INUM (count);
- else if (scm_is_signed_integer (count, LONG_MIN + 1, LONG_MAX))
- /* We exclude LONG_MIN to ensure that 'bits_to_shift' can be
- negated without overflowing. */
- bits_to_shift = scm_to_long (count);
- else if (scm_is_true (scm_negative_p (scm_sum (scm_integer_length (n),
- count)))
- || scm_is_true (scm_zero_p (n)))
- /* If N is zero, or the right shift count exceeds the integer
- length, the result is zero. */
- return SCM_INUM0;
- else
- scm_num_overflow ("round-ash");
-
- if (bits_to_shift > 0)
- return left_shift_exact_integer (n, bits_to_shift);
- else if (SCM_LIKELY (bits_to_shift < 0))
- return round_right_shift_exact_integer (n, -bits_to_shift);
- else
- return n;
- }
- else
+ if (!SCM_I_INUMP (n) && !SCM_BIGP (n))
SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
+
+ if (scm_is_true (scm_negative_p (scm_sum (scm_integer_length (n),
+ count)))
+ || scm_is_true (scm_zero_p (n)))
+ /* If N is zero, or the right shift count exceeds the integer
+ length, the result is zero. */
+ return SCM_INUM0;
+ else if (scm_is_signed_integer (count, INT32_MIN + 1, INT32_MAX)) {
+ /* We exclude MIN to ensure that 'bits_to_shift' can be
+ negated without overflowing, if INT32_MIN happens to be LONG_MIN */
+ long bits_to_shift = scm_to_long (count);
+ if (bits_to_shift > 0)
+ return left_shift_exact_integer (n, bits_to_shift);
+ else if (SCM_LIKELY (bits_to_shift < 0))
+ return round_right_shift_exact_integer (n, -bits_to_shift);
+ else
+ return n;
+ } else
+ scm_num_overflow ("round-ash");
}
#undef FUNC_NAME
diff --git a/test-suite/tests/numbers.test b/test-suite/tests/numbers.test
index 8f644874d..51263f0ac 100644
--- a/test-suite/tests/numbers.test
+++ b/test-suite/tests/numbers.test
@@ -5466,7 +5466,10 @@
(ash-variant -1 (- (expt 2 1000))))
(pass-if-exception "Huge left shift of non-zero => numerical overflow"
exception:numerical-overflow
- (ash-variant 123 (expt 2 1000)))))
+ (ash-variant 123 (expt 2 1000)))
+ (pass-if-exception "Shift large enough to cause gmp abort in 3.0.7"
+ exception:numerical-overflow
+ (ash-variant 1 (expt 2 37)))))
(test-ash-variant 'ash ash floor #f)
(test-ash-variant 'round-ash round-ash round #t)
--
2.33.1
[-- Attachment #3: 0002-Avoid-ash-with-arguments-that-might-overflow-in-lang.patch --]
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From 47f99500e68e40f34a1dab8b0350f32c2ed62d9d Mon Sep 17 00:00:00 2001
From: Daniel Llorens <lloda@sarc.name>
Date: Thu, 4 Nov 2021 16:02:42 +0100
Subject: [PATCH 2/2] Avoid ash with arguments that might overflow in (language
cps types)
Fixes https://debbugs.gnu.org/50609
* module/languages/cps/types.scm (ulsh): As stated.
---
module/language/cps/types.scm | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/module/language/cps/types.scm b/module/language/cps/types.scm
index d3be176bf..87c58d5bc 100644
--- a/module/language/cps/types.scm
+++ b/module/language/cps/types.scm
@@ -1444,7 +1444,9 @@ minimum, and maximum."
(define! result &s64 &s64-min &s64-max))))
(define-type-inferrer (ulsh a b result)
- (if (<= (ash (&max/u64 a) (&max/u64 b)) &u64-max)
+ (if (and
+ (or (zero? (&max/u64 a)) (< (&max/u64 b) 64)) ; don't even try
+ (<= (ash (&max/u64 a) (&max/u64 b)) &u64-max))
;; No overflow; we can be precise.
(define! result &u64
(ash (&min/0 a) (&min/0 b))
--
2.33.1
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