Bug 16965 - MemoryMappedFile.CreateFromFile ("/dev/mem") throws ArgEx on "capacity"
Summary: MemoryMappedFile.CreateFromFile ("/dev/mem") throws ArgEx on "capacity"
Alias: None
Product: Class Libraries
Classification: Mono
Component: System.Core ()
Version: master
Hardware: PC Linux
: --- major
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2013-12-25 06:52 UTC by Alex Rønne Petersen
Modified: 2014-01-06 15:54 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

Notice (2018-05-24): bugzilla.xamarin.com is now in read-only mode.

Please join us on Visual Studio Developer Community and in the Xamarin and Mono organizations on GitHub to continue tracking issues. Bugzilla will remain available for reference in read-only mode. We will continue to work on open Bugzilla bugs, copy them to the new locations as needed for follow-up, and add the new items under Related Links.

Our sincere thanks to everyone who has contributed on this bug tracker over the years. Thanks also for your understanding as we make these adjustments and improvements for the future.

Please create a new report on GitHub or Developer Community with your current version information, steps to reproduce, and relevant error messages or log files if you are hitting an issue that looks similar to this resolved bug and you do not yet see a matching new report.

Related Links:

Description Alex Rønne Petersen 2013-12-25 06:52:24 UTC
csharp> System.IO.MemoryMappedFiles.MemoryMappedFile.CreateFromFile ("/dev/mem");
System.ArgumentException: capacity
Comment 1 Zoltan Varga 2014-01-04 18:17:48 UTC
This happens because MemoryMappedFile.Open () tries to obtain the size of the file, and /dev/mem has a size of 0.
Comment 2 Alex Rønne Petersen 2014-01-06 14:57:36 UTC
Is there any way to work around this?

Looking at our implementation, we don't actually use the capacity anywhere other than for reporting exceptions when the MMF is created. I see now that this is a requirement of the API, but it seems like this effectively renders the API unusable on a lot of special Unix files.

Would it be reasonable to diverge from the API by allowing a capacity of zero?
Comment 3 Zoltan Varga 2014-01-06 15:31:04 UTC
I think its fine to change this on unix.
Comment 4 Alex Rønne Petersen 2014-01-06 15:54:28 UTC
Restriction lifted in: https://github.com/mono/mono/commit/d8feb5e9adcc10e6733aedcc6aecee98b1a7c308