Date: Wed, 27 Feb 2008 13:54:46 -0500 From: Garrett Wollman <wollman@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: arch@freebsd.org Subject: Re: Cleaning up FILE in stdio.. Message-ID: <18373.45558.444085.196189@hergotha.csail.mit.edu> In-Reply-To: <200802271134.04166.jhb@freebsd.org> References: <200802262251.m1QMp7bV021709@hergotha.csail.mit.edu> <200802270526.m1R5QQT3024163@hergotha.csail.mit.edu> <200802271134.04166.jhb@freebsd.org>
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<<On Wed, 27 Feb 2008 11:34:04 -0500, John Baldwin <jhb@freebsd.org> said:
> I avoided EMFILE in all 3 cases as it struck me as being not really true (an
> app would find the rlimit higher than the current fd for example). Also,
> EMFILE doesn't really make sense from fdopen() at all. You've already opened
> the fd, so you know you can't run out of fd's.
[EMFILE] is does not imply that you have run out of fds. POSIX
says (for fdopen()):
The fdopen( ) function may fail if:
[EBADF] The fildes argument is not a valid file descriptor.
[EINVAL] The mode argument is not a valid mode.
[EMFILE] {FOPEN_MAX} streams are currently open in the
calling process.
[EMFILE] {STREAM_MAX} streams are currently open in the
calling process.
[ENOMEM] Insufficient space to allocate a buffer.
My change to sysconf() causes {STREAM_MAX} to be clamped at
{SHRT_MAX}, so a user calling sysconf(_PC_STREAM_MAX) or
$(getconf STREAM_MAX) will see a different value from the resource
limit and understand that there is a limit (even if it's not quite on
the number of streams).
For fopen(), the errors are defined as follows:
"shall fail":
[EMFILE] {OPEN_MAX} file descriptors are currently open in the calling
process.
[ENFILE] The maximum allowable number of files is currently open in
the system.
"may fail":
[EINVAL] The value of the mode argument is not valid.
[EMFILE] {FOPEN_MAX} streams are currently open in the calling
process.
[EMFILE] {STREAM_MAX} streams are currently open in the calling
process.
The other possibility would be [EOVERFLOW], which is defined as:
[EOVERFLOW] The named file is a regular file and the size of the file
cannot be represented correctly in an object of type off_t.
But I truly believe that [EMFILE] is the best option.
-GAWollman
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