Remove local source copied zlib files

[larshg]

External zlib has been default and is the preferred usage.

Makes #6396 obsolete.

[mvieth]

I think I would keep the HAVE_ZLIB preprocessor-define and the WITH_SYSTEM_ZLIB option, and either warn or error-out if WITH_SYSTEM_ZLIB is FALSE. That's a smoother transition for people who use one or the other. And zlib.cmake can probably be removed now?

[larshg]

Have updated accordingly.

[Copilot]

Pull request overview

This pull request removes locally bundled zlib source files from the PCL codebase and transitions to using external system zlib exclusively. The PR description states "External zlib has been default and is the preferred usage."

Changes:

• Removes all local zlib source and header files from surface/src/3rdparty/opennurbs/ and surface/include/pcl/surface/3rdparty/opennurbs/
• Removes zlib.cmake build configuration file
• Updates CMakeLists.txt files to require external ZLIB package and use the modern ZLIB::ZLIB target
• Simplifies header files to always use external zlib instead of conditionally using bundled zlib
• Adds deprecation warning for WITH_SYSTEM_ZLIB option

Reviewed changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
surface/src/on_nurbs/fitting_curve_2d_asdm.cpp	UNRELATED: Removes m_data->interior_normals.clear() call - appears to be an accidental inclusion
surface/src/3rdparty/opennurbs/*.c	Removes all bundled zlib C source files (zutil, uncompr, trees, inftrees, inflate, inffast, infback, crc32, compress, adler32)
surface/src/3rdparty/opennurbs/zlib.cmake	Removes zlib CMake configuration file
surface/src/3rdparty/opennurbs/opennurbs_zlib.cpp	Removes conditional compilation blocks for bundled zlib, adds include for pcl_config.h
surface/include/pcl/surface/3rdparty/opennurbs/*.h	Removes all bundled zlib header files (zutil, zconf, trees, opennurbs_zlib, inftrees, inflate, inffixed, inffast, examples_linking_pragmas, deflate)
surface/CMakeLists.txt	Replaces conditional zlib logic with required find_package(ZLIB) and uses modern ZLIB::ZLIB target
io/CMakeLists.txt	Adds ZLIB to optional dependencies and links ZLIB::ZLIB when PNG is found
CMakeLists.txt	Deprecates WITH_SYSTEM_ZLIB option and always searches for system ZLIB

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[Copilot]

This line deletion appears to be unrelated to the purpose of this PR which is to remove local zlib files. The removal of m_data->interior_normals.clear() is a functional change to the code logic. Looking at the rest of the function, interior_normals is still being used at lines 275, 331, and 341, so this deletion may cause inconsistent state. This change should either be removed from this PR or explained in the PR description if it's intentional.

[mvieth]

Why did you remove examples_linking_pragmas.h? That belongs to opennurbs, not zlib

[mvieth]

Suggested change

	message(WARNING "WITH_SYSTEM_ZLIB option is deprecated, has no effect and will be removed in 1.18.")
	if(NOT WITH_SYSTEM_ZLIB)
	message(WARNING "WITH_SYSTEM_ZLIB option is deprecated, has no effect and will be removed in 1.18.")
	endif()

Maybe like this, so that the warning is not always displayed, only when someone chooses the deprecated behaviour?

[larshg]

Yeah, I guess when we remove it, people will just see a warning if the supply the argument on cmake call, that it won't be used. Thats why I went with showing always. Maybe it can be checked if the variable is defined or not and if defined, then we print the message.

[larshg]

Ahh, maybe I was too quick - I probably removed since I saw zlib in there: https://github.com/PointCloudLibrary/pcl/pull/6399/changes#diff-a4d0602f96c844e85341ecf937a6d4d39aeb46a4c8acbc51fda8ee7a67033450L62

But we can keep it.

[mvieth]

Okay sure, the CMake default not-used warning is fine, too.