0005463: map_file fails to map to empty bigarray

(0006587)
dbuenzli (reporter)
2012-01-04 10:44

On

> uname -v
Darwin Kernel Version 10.8.0: Tue Jun 7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386

the man says :

[...]

COMPATIBILITY
     mmap() now returns with errno set to EINVAL in places that historically
     succeeded. The rules have changed as follows:

     o The flags parameter must specify either MAP_PRIVATE or MAP_SHARED.

     o The size parameter must not be 0.

     o The off parameter must be a multiple of pagesize, as returned by
         sysconf().

(0006588)
gerd (reporter)
2012-01-04 14:18

@dbuenzli: map_file allows it to map files at offsets that are not a multiple of the pagesize. This is done by rounding down to the next multiple, and hiding the intitial part of the mapping from the user. What I want to say is that it does not necessarily matter what mmap allows when there is a way to emulate more general behavior.

I think an emulation for size=0 is very easy - just return the empty array instead (don't call mmap at all).

(0006698)
xleroy (administrator)
2012-01-17 16:31

Thanks for the analysis. The proposed fix looks good to me. To be implemented some day.

(0007299)
xleroy (administrator)
2012-04-09 12:26

Gerd's solution implemented in commit 12326 in version/4.00, 12327 in trunk.

Issue History
Date Modified	Username	Field	Change
2012-01-04 09:44	Martin Jambon	New Issue
2012-01-04 10:44	dbuenzli	Note Added: 0006587
2012-01-04 14:18	gerd	Note Added: 0006588
2012-01-17 16:31	xleroy	Note Added: 0006698
2012-01-17 16:31	xleroy	Status	new => confirmed
2012-04-09 12:26	xleroy	Note Added: 0007299
2012-04-09 12:26	xleroy	Status	confirmed => resolved
2012-04-09 12:26	xleroy	Resolution	open => fixed
2012-04-09 12:26	xleroy	Fixed in Version	=> 4.00.0+dev

Notes
(0006587) dbuenzli (reporter) 2012-01-04 10:44	On > uname -v Darwin Kernel Version 10.8.0: Tue Jun 7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 the man says : [...] COMPATIBILITY mmap() now returns with errno set to EINVAL in places that historically succeeded. The rules have changed as follows: o The flags parameter must specify either MAP_PRIVATE or MAP_SHARED. o The size parameter must not be 0. o The off parameter must be a multiple of pagesize, as returned by sysconf().

(0006588) gerd (reporter) 2012-01-04 14:18	@dbuenzli: map_file allows it to map files at offsets that are not a multiple of the pagesize. This is done by rounding down to the next multiple, and hiding the intitial part of the mapping from the user. What I want to say is that it does not necessarily matter what mmap allows when there is a way to emulate more general behavior. I think an emulation for size=0 is very easy - just return the empty array instead (don't call mmap at all).

(0006698) xleroy (administrator) 2012-01-17 16:31	Thanks for the analysis. The proposed fix looks good to me. To be implemented some day.

(0007299) xleroy (administrator) 2012-04-09 12:26	Gerd's solution implemented in commit 12326 in version/4.00, 12327 in trunk.

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