Re: Threads: incompatibilities between C and C++?

Rani Sharoni <>
Thu, 24 May 2012 02:11:58 -0700 (PDT)
On May 23, 10:27 pm, Pete Becker <> wrote:

On 2012-05-23 08:25:27 +0000, Rani Sharoni said:

Rani Sharoni wrote:

[...]> might add a bit more to my confusion:

"Synchronization: The completion of the invocation of the
constructor synchronizes with the beginning of the invocation of
the copy of f."

I'm not sure about the meaning of this paragraph and why it's
actually required.

int i = 0;

void f() {
        assert(i == 3);


int main() {
        i = 3;
        std::thread thr(f);
        return 0;


By abstracting the notion of *synchronizes with*, the memory model
lets you talk about less stringent visiblity requirements
(release/acquire, release/consume, and relaxed) without having to
repeat their definitions everywhere they apply.

Thanks for the explanation. I see your point. std::create-thread is a
full memory barrier so for example there is no need for additional
barriers in order to access (from the new thread) memory that was
initialized before the create-thread call (i.e. no re-ordering is
allowed by the caller). I guess that every threading platform
(including thread pools) provide such guarantee.


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