From: Daniel Santos <daniel@gsat.us>
To: Khem Raj <raj.khem@gmail.com>,
musl@lists.openwall.com, Daniel Santos <daniel.santos@pobox.com>
Subject: Re: [musl] [PATCH] Fix signed compare warning
Date: Thu, 25 Jun 2020 23:31:32 -0500 [thread overview]
Message-ID: <bd78cf74-6ed4-3fb0-b7e3-fe084e388ff2@gsat.us> (raw)
In-Reply-To: <39be4d66-963c-4e06-e685-37a8396d10c3@gmail.com>
On 6/25/20 10:58 AM, Khem Raj wrote:
>
> On 6/24/20 4:20 PM, Daniel Santos wrote:
>> Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
>> ---
>> src/thread/__timedwait.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/thread/__timedwait.c b/src/thread/__timedwait.c
>> index 666093be..9829b93e 100644
>> --- a/src/thread/__timedwait.c
>> +++ b/src/thread/__timedwait.c
>> @@ -38,7 +38,7 @@ int __timedwait_cp(volatile int *addr, int val,
>> if (priv) priv = FUTEX_PRIVATE;
>>
>> if (at) {
>> - if (at->tv_nsec >= 1000000000UL) return EINVAL;
>> + if ((unsigned long)at->tv_nsec >= 1000000000UL) return EINVAL;
>> if (__clock_gettime(clk, &to)) return EINVAL;
>> to.tv_sec = at->tv_sec - to.tv_sec;
>> if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
>>
> may be use < 0 || >= 1000000000L and avoid the cast.
> there is a similar issue in src/thread/pthread_cond_timedwait.c as well
Thank you for that. I'll resubmit changing both instances.
In this case, the POSIX spec requires nt_nsec to be a long (
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/time.h.html
). Either way, a good optimizer should convert this into an unsigned
compare. My early years in 6502 assembly sort-of shapes my thinking, as
I try to write higher level code as similarly to the assembly I presume
the compiler will emit. But if the project has a strong preference to
avoid casts, I can change it.
Thanks!
Daniel
next prev parent reply other threads:[~2020-06-26 6:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 23:20 Daniel Santos
2020-06-25 15:58 ` Khem Raj
2020-06-25 17:33 ` Rich Felker
2020-06-26 4:31 ` Daniel Santos [this message]
2020-06-26 6:26 ` Jeffrey Walton
2020-07-04 21:13 ` Daniel Santos
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