Re: [PATCH RFC] Large file support (LFS) for can-utils

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello Oliver,

On Fri, Feb 21, 2014 at 09:21:04PM +0100, Oliver Hartkopp wrote:
> yesterday I tried to create a really big CAN logfile with
> 
> 	candump -l any
> 
> logging 9 CAN interfaces.
> 
> But unfortunately the length of the log file on my 32 bit i686 machine was
> limited to 2147483647 == 0x7FFFFFFF == int32 max ...
> 
> I did some investigation and there's some kind of large file support (LFS) in
> recent gnu libraries that allow 32 bit applications to create large files with
> file length values > 0x7FFFFFFF when the filesystem supports it.
> 
> When applying the patch below my candump was able to create a large log file.
> 
> Alternatively
> 
> 	candump -L any > filename
> 
> did the job too as obviously 'cat' has large file support ;-)
<pedantic>
There is no cat involved, > is handled by your shell.
</pedantic>
Doesn't really make a difference though.

> What do you think about LFS?
> Would this be the correct way to add the LFS support?
Maybe:

	CFLAGS += $(getconf LFS_CFLAGS)
	LDFLAGS += $(getconf LFS_LDFLAGS)

but on the other hand autoconf does it differently, they set

	_FILE_OFFSET_BITS=64
 
only if it's needed (assuming I understood that autoconf m4 stuff
correctly). Also LDFLAGS are not handled at all by autoconf.

> diff --git a/Makefile b/Makefile
> index ab99746..a926177 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -45,6 +45,7 @@ MAKEFLAGS = -k
> 
>  CFLAGS    = -O2 -Wall -Wno-parentheses -Iinclude \
>  	    -fno-strict-aliasing \
> +	    -D_FILE_OFFSET_BITS=64 \
>  	    -DSO_RXQ_OVFL=40 \
>  	    -DPF_CAN=29 \
>  	    -DAF_CAN=PF_CAN
> 
-DVAR=VAL should better go into CPPFLAGS.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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