* [PULL 0/1] Miscellaneous patches for 2019-11-25
@ 2019-11-25 6:04 Markus Armbruster
2019-11-25 6:04 ` [PULL 1/1] util/cutils: Fix incorrect integer->float conversion caught by clang Markus Armbruster
2019-11-25 15:47 ` [PULL 0/1] Miscellaneous patches for 2019-11-25 Peter Maydell
0 siblings, 2 replies; 3+ messages in thread
From: Markus Armbruster @ 2019-11-25 6:04 UTC (permalink / raw)
To: qemu-devel
The following changes since commit 2061735ff09f9d5e67c501a96227b470e7de69b1:
Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging (2019-11-21 17:18:40 +0000)
are available in the Git repository at:
git://repo.or.cz/qemu/armbru.git tags/pull-misc-2019-11-25
for you to fetch changes up to 25f74087c695364dfaa87443b1040a3aa5c29008:
util/cutils: Fix incorrect integer->float conversion caught by clang (2019-11-25 06:00:05 +0100)
----------------------------------------------------------------
Miscellaneous patches for 2019-11-25
----------------------------------------------------------------
Fangrui Song (1):
util/cutils: Fix incorrect integer->float conversion caught by clang
util/cutils.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--
2.21.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PULL 1/1] util/cutils: Fix incorrect integer->float conversion caught by clang
2019-11-25 6:04 [PULL 0/1] Miscellaneous patches for 2019-11-25 Markus Armbruster
@ 2019-11-25 6:04 ` Markus Armbruster
2019-11-25 15:47 ` [PULL 0/1] Miscellaneous patches for 2019-11-25 Peter Maydell
1 sibling, 0 replies; 3+ messages in thread
From: Markus Armbruster @ 2019-11-25 6:04 UTC (permalink / raw)
To: qemu-devel; +Cc: Fangrui Song, Richard Henderson, Juan Quintela
From: Fangrui Song <i@maskray.me>
Clang does not like do_strtosz()'s code to guard against overflow:
qemu/util/cutils.c:245:23: error: implicit conversion from 'unsigned long' to 'double' changes value from 18446744073709550592 to 18446744073709551616 [-Werror,-Wimplicit-int-float-conversion]
The warning will be enabled by default in clang 10. It is not
available for clang <= 9.
val * mul >= 0xfffffffffffffc00 is indeed wrong. 0xfffffffffffffc00
is not representable exactly as double. It's half-way between the
representable values 0xfffffffffffff800 and 0x10000000000000000.
Which one we get is implementation-defined. Bad.
We want val * mul > (the largest uint64_t exactly representable as
double). That's 0xfffffffffffff800. Write it as nextafter(0x1p64, 0)
with a suitable comment.
Signed-off-by: Fangrui Song <i@maskray.me>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Patch split, commit message improved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20191122080039.12771-3-armbru@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
util/cutils.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/util/cutils.c b/util/cutils.c
index fd591cadf0..77acadc70a 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -239,10 +239,12 @@ static int do_strtosz(const char *nptr, const char **end,
goto out;
}
/*
- * Values >= 0xfffffffffffffc00 overflow uint64_t after their trip
- * through double (53 bits of precision).
+ * Values near UINT64_MAX overflow to 2**64 when converting to double
+ * precision. Compare against the maximum representable double precision
+ * value below 2**64, computed as "the next value after 2**64 (0x1p64) in
+ * the direction of 0".
*/
- if ((val * mul >= 0xfffffffffffffc00) || val < 0) {
+ if ((val * mul > nextafter(0x1p64, 0)) || val < 0) {
retval = -ERANGE;
goto out;
}
--
2.21.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PULL 0/1] Miscellaneous patches for 2019-11-25
2019-11-25 6:04 [PULL 0/1] Miscellaneous patches for 2019-11-25 Markus Armbruster
2019-11-25 6:04 ` [PULL 1/1] util/cutils: Fix incorrect integer->float conversion caught by clang Markus Armbruster
@ 2019-11-25 15:47 ` Peter Maydell
1 sibling, 0 replies; 3+ messages in thread
From: Peter Maydell @ 2019-11-25 15:47 UTC (permalink / raw)
To: Markus Armbruster; +Cc: QEMU Developers
On Mon, 25 Nov 2019 at 06:06, Markus Armbruster <armbru@redhat.com> wrote:
>
> The following changes since commit 2061735ff09f9d5e67c501a96227b470e7de69b1:
>
> Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging (2019-11-21 17:18:40 +0000)
>
> are available in the Git repository at:
>
> git://repo.or.cz/qemu/armbru.git tags/pull-misc-2019-11-25
>
> for you to fetch changes up to 25f74087c695364dfaa87443b1040a3aa5c29008:
>
> util/cutils: Fix incorrect integer->float conversion caught by clang (2019-11-25 06:00:05 +0100)
>
> ----------------------------------------------------------------
> Miscellaneous patches for 2019-11-25
>
> ----------------------------------------------------------------
> Fangrui Song (1):
> util/cutils: Fix incorrect integer->float conversion caught by clang
>
> util/cutils.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> --
Applied, thanks.
Please update the changelog at https://wiki.qemu.org/ChangeLog/4.2
for any user-visible changes.
-- PMM
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-11-25 6:04 [PULL 0/1] Miscellaneous patches for 2019-11-25 Markus Armbruster
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2019-11-25 15:47 ` [PULL 0/1] Miscellaneous patches for 2019-11-25 Peter Maydell
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