[ITK] compiling itk on freebsd, how to flag out ldl?

Tue Feb 14 16:32:42 EST 2017

Hi,

Are we sure the first case was not close to mostly working? Did other wrapped language link OK? did SimpleITK tests link OK? If ITK tests are enable with ITK_DYNAMIC_LOADING:BOOL=0 do they compile and work? We need to know if ITK is OK before moving to SimpleITK.

@Matt
I am not very familiar with CMAKE_DL_LIBS either [1]. I know Matt added the ITK_DYNAMIC_LOADING CMake variable to ITK, so he may have insight into this problem too. My guess is that CMAKE_DL_LIBS variable is not entered into the cache but CMake provides a default value for platform. I expect you can overrride it with command line values.

I hacked a patch to enable CMAKE_DL_LIBS to propgate down from the Superbuild [2]. If you checkout that path you should be able to do a supberbuild of -DCMAKE_DL_LIBS=“”. That may work, but I don’t know for sure.

HTH,
Brad

[1] https://cmake.org/cmake/help/v3.0/variable/CMAKE_DL_LIBS.html
[2] https://github.com/SimpleITK/SimpleITK/pull/104

On Feb 14, 2017, at 3:53 PM, Longzhu Shen <lqshen10 at gmail.com<mailto:lqshen10 at gmail.com>> wrote:

Hi Brad,

Many thanks for the advice.
I made an attempt to follow the first approach but it did not seem
work. Here is what I did and the errors I got.

-----------------------------------------------------
$ cmake ../SuperBuild -DITK_DYNAMIC_LOADING:BOOL=0

[ 80%] Building CXX object
Wrapping/Python/CMakeFiles/SimpleITK_PYTHON.dir/sitkPyCommand.cxx.o
[ 80%] Building CXX object
Wrapping/Python/CMakeFiles/SimpleITK_PYTHON.dir/SimpleITKPYTHON_wrap.cxx.o
[ 80%] Linking CXX executable bin/SimpleITKTclsh
/usr/bin/ld: cannot find -ldl
c++: error: linker command failed with exit code 1 (use -v to see
invocation)
--- Wrapping/Tcl/bin/SimpleITKTclsh ---
*** [Wrapping/Tcl/bin/SimpleITKTclsh] Error code 1
-----------------------------------------------------

I planned to try the 2nd approach. However, I could not find the
CMAKE_DL_LIBS easily. I checked the subfolder of Superbuild,
and SimpleITK-build/ITK-build. I did not find it in
Code/Common/src/CMakeLists.txt as well.

The only place I found "CMAKE_DL_LIBS" is in the file
CMake/sitkTargetLinkLibrariesWithDynamicLookup.cmake

279:        target_link_libraries(main \"${CMAKE_DL_LIBS}\")

I was wondering I may get further directions to modify CMAKE_DL_LIBS
variable. Many thanks.

sincerely,

Longzhu

Lowekamp @ 2017-02-14 15:36 UTC:

Hello Longzu,

You are using freebsd, that is new and exciting. I have not used that OS for developing.

There are two things in the ITK/SimpleITK build that are related to this.

First, there is an option in ITK ( which I have not used ) call ITK_DYNAMIC_LOADING. If you pass -DITK_DYNAMIC_LOADING:BOOL=0 to cmake for the Superbuild, it should propagate to the ITK project and this feature will be remove. This may solve your problem.

The second is CMake variable CMAKE_DL_LIBS. I believe it is the dl library that is causing the problem [1]. Setting it to an empty string may also remove it from the linking lines. Getting that to propagate to the ITK project will not happen automatically and would need to be done manually in the ITK build.

HTH,
Brad

[1] https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/Core/Common/src/CMakeLists.txt#L142

________________________________________
From: Longzhu Shen [lqshen10 at gmail.com<mailto:lqshen10 at gmail.com>]
Sent: Tuesday, February 14, 2017 9:11 AM
To: community at itk.org<mailto:community at itk.org>
Subject: [ITK] compiling itk on freebsd, how to flag out ldl?

Hello,

I'm trying to compile simpleitk on my freebsd system.
The issue I encountered is ldl is not found.
After some searching, I found libdl is not needed on freebsd. It is
included in libc. Wondering how I can turn it off in the make file.
I did not find  ldl in the Makefile under Simpleitk-build.

I followed the instrutions from the link below.

https://chsasank.github.io/sitk-docs/building/unix.html#obtaining-source-code

Thanks.

Longzhu

--
Longzhu Shen, Ph.D.
Postdoc Research Associate
School of Forestry and Environmental Studies
Yale University
195 Prospect Street
New Haven, CT 06511

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