fseek() vs. fseeko()

Ralf Corsepius ralf.corsepius@rtems.org
Fri Jun 29 22:13:00 GMT 2012

On 06/20/2012 04:07 PM, Joel Sherrill wrote:
> On 06/20/2012 08:54 AM, Ralf Corsepius wrote:
>> On 06/20/2012 03:41 PM, Joel Sherrill wrote:
>>> On 06/19/2012 09:42 AM, Sebastian Huber wrote:
>>>> On 06/19/2012 04:08 PM, Corinna Vinschen wrote:
>>>>> Along these lines, fgetpos and fsetpos are a bit tricky since they
>>>>> depend on the definition of fpos_t in include/stdio.h. Right now,
>>>>> only Cygwin defines fpos_t as 64 bit type in stdio.h, all other
>>>>> targets define fpos_t as 32 bit and fpos64_t as 64 bit type to make
>>>>> a clear distinction between the 32 bit and the 64 bit set of
>>>>> functions.
>>> Speaking for myself, I would like the methods to default to all 64-bit
>>> versions on RTEMS (when the CPU defaults to 64-bit).
>> This is non-reasonable, because it's unsuiteable for "small" targets,
>> ineffective on some architectures and a waste of resources for some
>> applications.
> Hence the parenthetical phrase "(when the CPU defaults to 64-bit)"
> We choose 32-bit or 64-bit off_t as the default on a per CPU basis
> and whichever it is, all methods without an explicit number in the
> name should use the default type.
>>>> RTEMS has this in<machine/_types.h>:
>>> FWIW I think that list to use 64-bit types should be longer.
>> This list is hand-crafted for "big targets", based on user-demand.
> I have done two ports in the past few months and never looked
> at that list. Both should have been on the 64-bit list.

Well, you did not ask nor mention it anywhere ;-)

> It is another issue entirely but I think we need to make a
> conscious decision for every target.

As I wrote above this would be un-wise. Embedded application running on 
say avr/nios2/h8300/sh based-systems with very few 100kB of RAM will 
hardly ever need 64bit off_t's.

Esp. _you_, the person who often has added questionable measures to 
RTEMS "to reduce memory overhead" should know why.

Of course, this doesn't invalidate any reasoning to make off_t's 
configuration-time configurable - It would be nice-to-have. 
Unfortunately, this is not trivial to implement into newlib's configuration.


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