From: Florian Weimer <fweimer@redhat.com>
To: Mark Wielaard <mark@klomp.org>
Cc: libcurl development <curl-library@lists.haxx.se>,
Catalin Raceanu <cra@mega.nz>,
elfutils-devel@sourceware.org
Subject: Re: Using libcurl in another library, when/if to call curl_global_init?
Date: Tue, 05 Apr 2022 17:24:41 +0200 [thread overview]
Message-ID: <874k37y2me.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <YkWqdxmRuMHE2XnH@wildebeest.org> (Mark Wielaard's message of "Thu, 31 Mar 2022 15:19:51 +0200")
* Mark Wielaard:
> Hi,
>
> On Thu, Mar 31, 2022 at 04:00:16PM +0300, Catalin Raceanu via curl-library wrote:
>> On 31-Mar-22 15:04, Mark Wielaard wrote:
>> > whether there is a thread-safe way to call
>> > curl_global_init at a later time (to get rid of the library constructor
>> > init function).
>>
>> I believe that this is an exact fit for C==11's std::call_once(). Boost also
>> has an equivalent, that most likely predates the other, in case older c++
>> standard is used.
>
> Thanks. Our library is pure C, but we can probably rely on
> pthread_once if it is allowable to call curl_global_init at a later
> time when multiple threads are already running.
The problem is that every caller of pthread_once needs to use the same
pthread_once_t synchronization object, so you still have the same
problem.
I strongly believe that library-safe code needs to perform lazy
initialization, that is, initialize the library on first use, and do
that in a thread-safe manner. It solves the synchronization issue
between different users of the API, and it's the only way to report
errors properly (for example, a failure in an ELF constructor can only
be reported via process termination).
At least on Linux, the need to support multiple different threading
libraries is a thing of the past.
Thanks,
Florian
next prev parent reply other threads:[~2022-04-05 15:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-31 12:04 Mark Wielaard
[not found] ` <b424b435-482d-7d24-4337-8ef7437ab05c@mega.nz>
2022-03-31 13:19 ` Mark Wielaard
2022-04-05 15:24 ` Florian Weimer [this message]
2022-04-22 22:14 ` Mark Wielaard
2022-04-05 15:36 ` Daniel Stenberg
2022-04-05 16:19 ` Mark Wielaard
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