| Message ID | 20191122000045.vz3eq6s6aqkv6l6h@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] Fix incorrect integer->float conversions caught by clang -Wimplicit-int-float-conversion | expand |
Fangrui Song <i@maskray.me> writes: > On 2019-11-21, Eric Blake wrote: >>On 11/19/19 2:49 PM, Fangrui Song wrote: >> >>>> >>>>Can we simply drop the offending line statement instead? >>> >>>Fixed in the new patch. >>> >> >>>>The first val * mul above this range is 0x1p64. Rejecting it is >>>>correct, because it overflows yint64_t. >>> >>>I am not subscribed, so apologize that this email may be off the thread. >>> >>>(The binutils mailing list allows a user to download the raw email so I >>>can still reply to a specific email, but this list does not provide such >>>feature.) There's <https://lists.gnu.org/archive/mbox/qemu-devel/>. >> Actually, it's better to post a v2 patch as a new top-level thread, >> rather than buried as an attachment to a reply to v1, because our CI >> tooling doesn't see through the attachment (nor was it easy for me >> to reply to the v2 patch - I had to open the attachment to paste its >> text inline below...). >> >>More patch submission hints at https://wiki.qemu.org/Contribute/SubmitAPatch > > Retitled to [PATCH v2] Good, such versioning is essential to avoid confusion. Next time, start a new top-level thread for v2. Our patch submission processing (automated as well as human) expects that. I just did it for you: "[PATCH v3 0/2] Fix incorrect integer->float conversion caught by clang". Many thanks for your fixes!
From d533585df39083e88adc50b881a4be74125c837e Mon Sep 17 00:00:00 2001 From: Fangrui Song <i@maskray.me> Date: Fri, 15 Nov 2019 16:27:47 -0800 Subject: [PATCH] Fix incorrect integer->float conversion caught by clang -Wimplicit-int-float-conversion To: qemu-devel@nongnu.org The warning will be enabled by default in clang 10. It is not available for clang <= 9. qemu/migration/migration.c:2038:24: error: implicit conversion from 'long' to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-int-float-conversion] ... 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] Signed-off-by: Fangrui Song <i@maskray.me> --- migration/migration.c | 3 +-- util/cutils.c | 8 +++++--- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 354ad072fa..09b150663f 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -2035,11 +2035,10 @@ void qmp_migrate_set_downtime(double value, Error **errp) } value *= 1000; /* Convert to milliseconds */ - value = MAX(0, MIN(INT64_MAX, value)); MigrateSetParameters p = { .has_downtime_limit = true, - .downtime_limit = value, + .downtime_limit = (int64_t)value, }; qmp_migrate_set_parameters(&p, errp); 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; } -- 2.24.0