Re: [PATCH mh/lockfile-retry] lockfile: replace random() by rand()
- From
Junio C Hamano <gitster@pobox.com>
- Date
- May 30, 2015, 17:12 UTC
- Message-ID
- <xmqq7frqat0m.fsf@gitster.dls.corp.google.com>
- In-Reply-To
- <55695770.2040303@kdbg.org>
Johannes Sixt <j6t@kdbg.org> writes:
> There you have it: Look the other way for a while, and people start > using exotic stuff... ;)
Is it exotic to have random/srandom? Both are in POSIX and 4BSD; admittedly rand/srand are written down in C89 and later, so they might be more portable, but I recall the prevailing wisdom is to favor random over rand for quality of randomness and portability, so I am wondering if it may be a better approach to keep the code as-is and do a compat/random.c based on either rand/srand (or use posix sample implementation [*1*]).
[Reference]
*1* http://pubs.opengroup.org/onlinepubs/9699919799/functions/rand.html
Show 30 quoted lines
>
> This is a build breakage of master on Windows. There are also a few
> new test suite failures. On of them is in t1404#2, indicating that
> a DF conflict takes a different error path. I haven't debugged, yet.
> The lock file retry test fails, too. I'll report back as time permits.
>
> lockfile.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lockfile.c b/lockfile.c
> index 5a93bc7..ee5cb01 100644
> --- a/lockfile.c
> +++ b/lockfile.c
> @@ -191,7 +191,7 @@ static int lock_file_timeout(struct lock_file *lk, const char *path,
> return lock_file(lk, path, flags);
>
> if (!random_initialized) {
> - srandom((unsigned int)getpid());
> + srand((unsigned int)getpid());
> random_initialized = 1;
> }
>
> @@ -218,7 +218,7 @@ static int lock_file_timeout(struct lock_file *lk, const char *path,
>
> backoff_ms = multiplier * INITIAL_BACKOFF_MS;
> /* back off for between 0.75*backoff_ms and 1.25*backoff_ms */
> - wait_us = (750 + random() % 500) * backoff_ms;
> + wait_us = (750 + rand() % 500) * backoff_ms;
> sleep_microseconds(wait_us);
> remaining_us -= wait_us;