Documentation/Snapshot/Developers/Overlinking Underlinking - Revision history

JChris.FillionR at 17:42, 3 March 2012

2012-03-03T17:42:08Z

JChris.FillionR: /* Should we use the --as-needed linker flags ? (see [1], [2], [3], [4]) ? */

2012-03-03T17:41:35Z

Should we use the --as-needed linker flags ? (see [1], [2], [3], [4]) ?

JChris.FillionR: /* Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ? */

2012-03-03T17:41:06Z

Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ?

JChris.FillionR: /* Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ? */

2012-03-03T17:39:37Z

Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ?

JChris.FillionR: /* Should we avoid the use of {VTK,ITK}_LIBRARIES and specify dependency explicitly when developing libraries depending on these toolkit ? */

2012-03-03T17:38:09Z

Should we avoid the use of {VTK,ITK}_LIBRARIES and specify dependency explicitly when developing libraries depending on these toolkit ?

JChris.FillionR: /* Questions */

2012-03-03T17:37:48Z

Questions

JChris.FillionR at 17:35, 3 March 2012

2012-03-03T17:35:48Z

JChris.FillionR: Created page with ' = Hypothesis = When building application on the top of our toolkits: VTK, ITK, etc .. .... we usually rely on the CMake variable named: VTK_LIBRARIES, ITK_LIBRARIES, …'

2012-03-03T17:35:37Z

Created page with ' = Hypothesis = When building application on the top of our toolkits: VTK, ITK, etc .. .... we usually rely on the CMake variable named: VTK_LIBRARIES, ITK_LIBRARIES, …'

New page

= Hypothesis =

When building application on the top of our toolkits: VTK, ITK, etc ..

.... we usually rely on the CMake variable named: VTK_LIBRARIES, ITK_LIBRARIES, ...

This implies that every targets linked using these variables will be linked against the complete list of libraries.

= Background =

* While working on issue associated with ITK_AUTOLOAD_FACTORY, I noticed that using tool like ldd was systematically listing all VTK and ITK libraries to list dependency of a custom factory. Using the "-u" flag helps to find out which library are not direct dependency ... doing so just doesn't "feel" right and make the all process tedious and time consuming.

* Then, instead of trying to work around the "issue", I decided to communicate with the rest of the team to get a better understanding of what we should be doing and, by extension, what we should be recommending to developers outside Kitware.

= Questions =

* Should we use the --as-needed linker flags ? (see [1], [2], [3], [4]) ?

* Should we avoid the use of {VTK,ITK}_LIBRARIES and specify dependency explicitly when developing libraries depending on these toolkit ?

* Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ? [Not sure if it already works that way]

* Would it speed up the "fixup" of libraries when generating packages on Mac ?

[1] http://linux.die.net/man/1/ld
[2] http://blog.flameeyes.eu/2009/07/01/does-as-needed-link-make-software-faster
[3] http://www.gentoo.org/proj/en/qa/asneeded.xml
[4] http://wiki.mandriva.com/en/Overlinking#Problems_introduced_by_--as-needed

← Older revision		Revision as of 17:42, 3 March 2012
Line 71:		Line 71:

	== Would it speed up the "fixup" of libraries when generating packages on Mac ? ==		== Would it speed up the "fixup" of libraries when generating packages on Mac ? ==
		+
		+	= Useful script =
		+
		+	I just created a small project hosting a convenient script that allow to ...
		+
		+	... discover on which toolkit (ITK, CTK or VTK) you cpp project is depending on.
		+
		+	See https://github.com/jcfr/HeaderToolkitDependencyWalker

@@ Line 19: / Line 19: @@
 * References:
-[1] http://linux.die.net/man/1/ld
+** [1] http://linux.die.net/man/1/ld
-[2] http://blog.flameeyes.eu/2009/07/01/does-as-needed-link-make-software-faster
+** [2] http://blog.flameeyes.eu/2009/07/01/does-as-needed-link-make-software-faster
-[3] http://www.gentoo.org/proj/en/qa/asneeded.xml
+** [3] http://www.gentoo.org/proj/en/qa/asneeded.xml
-[4] http://wiki.mandriva.com/en/Overlinking#Problems_introduced_by_--as-needed
+** [4] http://wiki.mandriva.com/en/Overlinking#Problems_introduced_by_--as-needed
 == Should we avoid the use of {VTK,ITK}_LIBRARIES and specify dependency explicitly when developing libraries depending on these toolkit ? ==

@@ Line 56: / Line 56: @@
 good approach, and so it may be a case of deciding on the best fit
 between these two approaches in my opinion.
 == Would it speed up the "fixup" of libraries when generating packages on Mac ? ==

← Older revision		Revision as of 17:39, 3 March 2012
Line 44:		Line 44:

	== Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ? ==		== Should we update VTK, ITK, ... build system to understand the COMPONENT parameters of find_package ? ==
		+
		+	=== Reply from Marcus D. Hanwell ===
		+	I would go with updating the build system to understand the COMPONENT
		+	parameters of find_package, and is what we plan to do with
		+	VTK_LIBRARIES at least. I would be interested in what others think
		+	here, but this seems like the best interface, and it allows the
		+	developers of these libraries some room to adjust the linked libraries
		+	if needed for certain special cases.
		+
		+	When using exported targets the use of explicit linking is also a very
		+	good approach, and so it may be a case of deciding on the best fit
		+	between these two approaches in my opinion.

	== Would it speed up the "fixup" of libraries when generating packages on Mac ? ==		== Would it speed up the "fixup" of libraries when generating packages on Mac ? ==

@@ Line 26: / Line 26: @@
 == Should we avoid the use of {VTK,ITK}_LIBRARIES and specify dependency explicitly when developing libraries depending on these toolkit ? ==
-* Reply from Ben Boeckel:
+=== Reply from Ben Boeckel ===
 This would be the way I'd go. It reduces the amount of work the linker
@@ Line 42: / Line 42: @@
 both *nix and Win32 (not that familiar with Mac) as well that dashboards
 should test.
 == Should we update VTK, ITK, ...  build system to understand the COMPONENT parameters of find_package ? ==
 == Would it speed up the "fixup" of libraries when generating packages on Mac ? ==

@@ Line 1: / Line 1: @@
 = Hypothesis =
 When building application on the top of our toolkits: VTK, ITK, etc ..
-       .... we usually rely on the CMake variable named: VTK_LIBRARIES, ITK_LIBRARIES, ...
+.... we usually rely on the CMake variable named: VTK_LIBRARIES, ITK_LIBRARIES, ...