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

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

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Status:
RESOLVED FIXED

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