Testcase:
$ uname -r
3.5.7-1.x86_64
$ cygcheck -f /bin/cp.exe
coreutils-9.6-1
$ for i in 1 2 3; do cat /bin/cygwin1.dll > file$i; done
$ compact /C file2 # NTFS compression
... (1.7 : 1) ...
$ compact /C /EXE:LZX file3 # Compact OS LZX compression
... (2.8 : 1) ...
$ stat -c '%b %s %n' file?
2928 2995253 file1
1720 2995253 file2
1044 2995253 file3
$ cp file1 copy1 # OK
$ cp file2 copy2 # Hangs
...[^C]
$ cp file3 copy3 # Hangs
...[^C]
$ md5sum file? copy?
2954646a9a0fe4579c3fc1f44dd4bb6a *file1
2954646a9a0fe4579c3fc1f44dd4bb6a *file2
2954646a9a0fe4579c3fc1f44dd4bb6a *file3
2954646a9a0fe4579c3fc1f44dd4bb6a *copy1
2954646a9a0fe4579c3fc1f44dd4bb6a *copy2
2954646a9a0fe4579c3fc1f44dd4bb6a *copy3
$ (sleep 2; pskill strace) & strace cp file3 copy3
...
47 2004141 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 0) #
SEEK_SET
46 2004187 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253 # EOF
47 2004234 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 3) #
SEEK_DATA
46 2004280 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253
47 2004327 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 4) #
SEEK_HOLE
46 2004373 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253
46 2004419 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 0)
51 2004470 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253
47 2004517 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 3)
47 2004564 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253
47 2004611 [main] cp 5546 lseek: 2995253 = lseek(3, 2995253, 4)
46 2004657 [main] cp 5546 fhandler_base::lseek: setting file pointer
to 2995253
Process strace killed.
file1/2 are detected as a possible sparse files but the optimized copy
algorithm does not properly handle the non-sparse case. Upstream bug?
Similar report for coreutils-9.5-1:
https://sourceware.org/pipermail/cygwin/2025-January/257082.html
--
Regards,
Christian
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