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Date: Wed, 12 Feb 2025 17:32:51 +0100
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Subject: /bin/cp of sparse files broken in 3.6.0-0.362.g68c13dc92f65.x86_64?
To: cygwin AT cygwin DOT com
From: Cedric Blancher via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Cedric Blancher <cedric DOT blancher AT gmail DOT com>
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Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

Good afternoon!

Is copying sparse files broken in 3.6.0-0.362.g68c13dc92f65.x86_64?

cp --version
cp (GNU coreutils) 9.5
Packaged by Cygwin (9.5-1

Checklist:
- Volume has FILE_SUPPORTS_SPARSE_FILES
- Cygwin mount has "sparse" option (mount Y: -o sparse,exec /cygdrive/y)
- source file has FILE_ATTRIBUTE_SPARSE_FILE set

But  cp --sparse=auto ... or any other combination of --sparse does
copy holes, i.e. turns 500GB of hole into 500GB of data (zero bytes).

echo "hello sparse file\n" >testcase17_sparse_begins_with_data && dd
if=/dev/null of=testcase17_sparse_begins_with_data oflag=append bs=1
count=1 seek=$((65536*512)) && echo "endoffile"
>>testcase17_sparse_begins_with_data

Ced
-- 
Cedric Blancher <cedric DOT blancher AT gmail DOT com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur

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