0005184: Bigarray.*.map_file doesn't work with some offsets on Windows

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0005184

OCaml

OCaml general

public

2010-11-29 16:40

2012-09-25 20:06

Reporter

Vadim_Z

Assigned To

xleroy

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

3.11.2

Target Version

Fixed in Version

Summary

0005184: Bigarray.*.map_file doesn't work with some offsets on Windows

Description

The function map_file from submodules of Bigarray module doesn't work as expected on Windows platform with some values of ~pos argument. Here's the example:

(* ======================================================= *)
open Bigarray ;;
open Unix ;;

let fd= openfile "z.out" [O_RDWR; O_CREAT; O_TRUNC] 0o666 in
begin
        let arr = Array1.map_file fd ~pos:(Int64.of_int 4096)
        int c_layout true 1 in
        arr.{0} <- 10
end;
close fd
;;
(* ======================================================= *)

Instead of writing the number to file the program yields:
Fatal error: exception Sys_error("The base address or the file offset specified does not have the proper alignment.
")

There's no such problem on Unix environment.

Additional Information

The problem is caused by the following: dwPageSize is used instead of dwAllocationGranularity as a unit when offset is determined for CreateFileMapping in file mmap_win32.c.

Replacing dwPageSize by dwAllocationGranularity everywhere in mmap_win32.c and recompilation of Bigarray library solved the problem for me.

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Notes
(0005920) doligez (manager) 2011-05-20 16:01	I can't reproduce this on windows 7 and cygwin with 3.12.0 or 3.11.2. Is this with mingw or the native MS port ?

(0005924) Vadim_Z (reporter) 2011-05-20 21:02	I've seen this behavior for native MS port. I expect that mingw port also fails there, as it uses the same file mmap_win32.c. On the other side, Cygwin port doesn't have this deficiency as it uses file mmap_unix.c and mmap function provided by the Cygwin environment.

(0005971) xleroy (administrator) 2011-06-04 15:54	Suggested fix to mmap_win32.c applied in 3.12 bugfix branch, will go in 3.12.1. Not tested.

Issue History
Date Modified	Username	Field	Change
2010-11-29 16:40	Vadim_Z	New Issue
2011-05-20 16:01	doligez	Note Added: 0005920
2011-05-20 16:01	doligez	Status	new => feedback
2011-05-20 21:02	Vadim_Z	Note Added: 0005924
2011-06-04 15:54	xleroy	Note Added: 0005971
2011-06-04 15:54	xleroy	Status	feedback => resolved
2011-06-04 15:54	xleroy	Resolution	open => fixed
2011-06-04 19:08	xleroy	Status	resolved => assigned
2011-06-04 19:08	xleroy	Assigned To	=> xleroy
2011-06-04 19:08	xleroy	Status	assigned => resolved
2012-09-25 20:06	xleroy	Status	resolved => closed