[cmake-developers] [CMake 0015837]: cmake_symlink_library fails on shared folders in Virtualbox with linux vm and linux host

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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https://public.kitware.com/Bug/view.php?id=15837 
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Reported By:                Friedrich
Assigned To:                
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Project:                    CMake
Issue ID:                   15837
Category:                   CMake
Reproducibility:            always
Severity:                   block
Priority:                   normal
Status:                     new
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Date Submitted:             2015-11-08 11:58 EST
Last Modified:              2015-11-08 11:58 EST
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Summary:                    cmake_symlink_library fails on shared folders in
Virtualbox with linux vm and linux host
Description: 
When building on a Linux-based vm in VirtualBox, on a Linux-based host, and
having the build directory inside a shared folder (with the host), the build
process fails at the step of linking shared libs, with error:
"cmake_symlink_library: System Error: Read-only file system"

Which seems bogus, as the build otherwise creates all build artifacts without
any problem in the very same directories.

Looking where things fail with strace shows it is the call
symlink("libxxx.so.0.17.20", "libxxx.so.1"):

lstat64("/srv/mer/targets/SailfishOS-i486/usr/bin/cmake", {st_mode=S_IFREG|0755,
st_size=3679756, ...}) = 0
getcwd("/home/src1/build/marble/src/lib/astro", 2048) = 38
getcwd("/home/src1/build/marble/src/lib/astro", 4097) = 38
readlink("/home/src1/build/marble/src/lib/astro/libastro.so.1", 0x77afe80b,
4096) = -1 ENOENT (No such file or directory)
access("libastro.so.1", R_OK)           = -1 ENOENT (No such file or directory)
getcwd("/home/src1/build/marble/src/lib/astro", 4097) = 38
lstat64("libastro.so.1", 0x77b00970)    = -1 ENOENT (No such file or directory)
getcwd("/home/src1/build/marble/src/lib/astro", 4097) = 38
symlink("libastro.so.0.17.20", "libastro.so.1") = -1 EROFS (Read-only file
system)
write(2, "CMake Error: cmake_symlink_libra"..., 71CMake Error:
cmake_symlink_library: System Error: Read-only file system) = 71
write(2, "\n", 1
)                       = 1

As I learned from https://www.virtualbox.org/ticket/10085 it seems shared
folders on VirtualBox do not support shared links out of the box (pun to be
done).
Half-official workaround is to use
VBoxManage setextradata VM_NAME
VBoxInternal2/SharedFoldersEnableSymlinksCreate/SHARE_NAME 1
(worked for me with virtualbox 5.0.8 at least)

No idea if cmake should and can support the case of no symlinks available in the
filesystem used for the builddir, as in the given case.
Just reporting to the experts, as the web search engine pointed to quite some
hits where people wondered about the same problem, so seems to be a more common
use case (e.g. setup as expected by
https://sailfishos.org/develop/tutorials/building-sailfish-os-packages-manually/
, where the example code given works, because it does not include shared libs
and thus not the symlinking step).
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Issue History 
Date Modified    Username       Field                    Change               
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2015-11-08 11:58 Friedrich      New Issue                                    
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