linux-kernel - Re: epoll_ctl and const correctness

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Message-ID: <84a01a8b0903251027p18fceee4h813f4d9616245a2d@mail.gmail.com>
Date:	Wed, 25 Mar 2009 18:27:03 +0100
From:	nicolas sitbon <nicolas.sitbon@...il.com>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: epoll_ctl and const correctness

Ok for "const correctness", but:
do you keep track of the structure event after the call to epoll_ctl or no?
I mean I found some codes that reuse this structure for multiple call
to epoll_ctl but with different file descriptor, is this allowed?

struct epoll_event ev = {.fd = STDIN_FILENO, .data.fd = STDIN_FILENO};
/* <= one structure for 2 calls */
epoll_ctl(epfd, EPOLL_CTL_ADD, STDIN_FILENO, &ev);
ev.fd = STDOUT_FILENO;
ev.data.fd = STDOUT_FILENO;
epoll_ctl(epfd, EPOLL_CTL_ADD, STDOUT_FILENO, &ev);

Other question:
int epoll_create(int size);

can you please, explain me why size is an int and not a size_t or at
least an unsigned integer?

thanks.

2009/3/25 Davide Libenzi <davidel@...ilserver.org>:
> On Wed, 25 Mar 2009, nicolas sitbon wrote:
>
>> Currently, the prototype of epoll_ctl is :
>>
>> int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
>>
>> I searched in the man of epoll_ctl and google, and it seems that the
>> structure pointed to by event isn't modify, valgrind confirms this
>> behaviour, so am I wrong? or the good prototype is
>>
>> int epoll_ctl(int epfd, int op, int fd, struct epoll_event const *event);
>
> According to the current ctl operations, yes. But doing that would prevent
> other non-const operations to be added later on.
>
>
> - Davide
>
>
>
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