COMP: Repair DCMTK build-tree export references for external consumers

[hjmjohnson]

Repair DCMTK's build-tree export after find_package(DCMTK) import — strip the DCMTK:: prefix from any link-interface reference that is not an existing target (all genuine DCMTK:: targets exist once DCMTKTargets.cmake is included) — so external consumers of an ITK build tree (e.g. an ANTs SuperBuild) survive CMake generate. Split out of #6543 at @blowekamp's request; the repair loop is line-for-line the fix proposed upstream in DCMTK/dcmtk#150, so it can be deleted verbatim when ITK's DCMTK pin includes that fix.

Merge-ordering note: once #6543's namespaced linking is in, an external build-tree consumer fails at generate without this repair (repro below); on pre-#6543 main the same consumer already fails, but later, at link (bare dcmdata names resolving against the system DCMTK). Install-tree consumers are unaffected either way.

Root cause

DCMTK's build-tree DCMTKTargets.cmake is written by the legacy export(TARGETS ... NAMESPACE DCMTK::), which prefixes DCMTK:: onto ITK's imported codec targets and records the nonexistent DCMTK::ITK::ITKZLIBModule (and TIFF/JPEG/PNG). An external consumer of an ITK build tree that resolves the DCMTK targets (where ITK_BINARY_DIR is unset in the find_package(ITK) scope) fails at generate. The install-tree export, written by install(EXPORT), resolves the same dependencies to their real ITK::* names and is unaffected.

Patching after import (in ITKDCMTK_EXPORT_CODE_BUILD) preserves the DCMTK_DIR seeding and every DCMTKConfig side effect, and corrects the targets regardless of import order. The "normal" fix is proposed upstream as DCMTK/dcmtk#150 (identical repair, shipped in DCMTKConfig.cmake itself); this in-ITK patch is the contained workaround until ITK's DCMTK pin includes it. The existence-checked form (rather than a DCMTK::ITK:: string replace) also covers the second defect shape found while building the upstream minimal repro: ALIAS targets are recorded de-aliased (e.g. DCMTK::super_zlibwrap), with no :: in the stripped name.

Minimal reproduction (verified)

1. Configure and build ITK at COMP: Link namespaced DCMTK targets in the DCMTK IO modules #6543's head (0a0a06c700a) with the vendored DCMTK:

cmake -S ITK -B ITK-build -G Ninja -DModule_ITKIODCMTK:BOOL=ON -DITK_USE_SYSTEM_DCMTK:BOOL=OFF
ninja -C ITK-build ITKIODCMTK
grep 'DCMTK::ITK::' ITK-build/DCMTKTargets.cmake   # the mis-prefixed entries

2. Configure a minimal external consumer against the build tree (use the same compiler as the ITK build):

# CMakeLists.txt
cmake_minimum_required(VERSION 3.22)
project(consumer CXX C)
find_package(ITK REQUIRED COMPONENTS ITKIODCMTK)
include(${ITK_USE_FILE})
add_executable(t main.cxx)
target_link_libraries(t ${ITK_LIBRARIES})

// main.cxx
#include "itkDCMTKImageIO.h"
int main() { auto io = itk::DCMTKImageIO::New(); return io.IsNull() ? 1 : 0; }

cmake -S consumer -B consumer-build -G Ninja -DITK_DIR=$PWD/ITK-build

3. Without this PR, generate fails:

CMake Error at .../ITK-build/DCMTKTargets.cmake:83 (set_target_properties):
  The link interface of target "DCMTK::dcmdata" contains:

    DCMTK::ITK::ITKZLIBModule

  but the target was not found.

4. With this PR applied on top of COMP: Link namespaced DCMTK targets in the DCMTK IO modules #6543, the consumer configures, generates, links, and runs (./consumer-build/t; echo $? → 0).

Testing performed

• Defect confirmed live: ITK-build/DCMTKTargets.cmake records DCMTK::ITK::ITK{ZLIB,TIFF,JPEG,PNG}Module; the generated build-tree Modules/ITKDCMTK.cmake contains the rewrite loop.
• Negative control on plain main: consumer generate passes (bare-name linking never resolves the broken DCMTK:: targets) but the final link fails against system DCMTK — the pre-existing breakage COMP: Link namespaced DCMTK targets in the DCMTK IO modules #6543 + this PR together eliminate.
• Positive control on COMP: Link namespaced DCMTK targets in the DCMTK IO modules #6543-only: consumer generate fails with the error above.
• Combined (COMP: Link namespaced DCMTK targets in the DCMTK IO modules #6543 head + this commit): consumer generate + link + run all succeed; 46/46 DCMTK tests pass.

Composes with #6543 (kept independent: applies and configures standalone on main).

[greptile-apps]

Greptile Summary

This PR repairs DCMTK build-tree exports for external ITK consumers. The main changes are:

• Re-imports DCMTK from the ITK build root for build-tree consumers.
• Rewrites missing DCMTK:: link-interface references after find_package(DCMTK).
• Leaves install-tree DCMTK lookup unchanged.

Confidence Score: 4/5

Safe after the suffixed-target case is handled.

The change is narrow, but the repair loop skips the actual exported target names when DCMTK_LIBRARY_SUFFIX is set.

Modules/ThirdParty/DCMTK/CMakeLists.txt

T-Rex Logs

What T-Rex did

• The suffixed-target repair scenario was reproduced using a deterministic harness that loads the repository CMakeLists.txt and models the suffixed DCMTK target.
• The run demonstrated that the build-tree repair loop iterates unsuffixed names, checks DCMTK::dcmdata, skips the repair, and leaves the suffixed target's final INTERFACE_LINK_LIBRARIES containing the ITKZLIBModule entry.
• Because CMake and Ninja were not available in PATH, the reproduction used a deterministic fallback script rather than a native CMake harness.
• Environment checks showed cmake, ninja, and pixi were not found while gcc/g++ were available, and the end-to-end runtime path could not be executed, so no runtime finding was reported.

_{Ran code and verified through T-Rex}

Important Files Changed

Filename	Overview
Modules/ThirdParty/DCMTK/CMakeLists.txt	Adds a build-tree DCMTK target link-interface repair loop, but it misses configurations using DCMTK_LIBRARY_SUFFIX.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
  participant Consumer as External build-tree consumer
  participant ITK as ITKConfig / module export code
  participant DCMTK as DCMTKConfig + DCMTKTargets
  Consumer->>ITK: find_package(ITK COMPONENTS ITKIODCMTK)
  ITK->>DCMTK: find_package(DCMTK) with build-tree DCMTK_DIR
  DCMTK-->>ITK: imports DCMTK:: targets
  ITK->>ITK: rewrite missing DCMTK:: link-interface entries
  ITK-->>Consumer: exposes corrected ITKIODCMTK dependencies

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%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
  participant Consumer as External build-tree consumer
  participant ITK as ITKConfig / module export code
  participant DCMTK as DCMTKConfig + DCMTKTargets
  Consumer->>ITK: find_package(ITK COMPONENTS ITKIODCMTK)
  ITK->>DCMTK: find_package(DCMTK) with build-tree DCMTK_DIR
  DCMTK-->>ITK: imports DCMTK:: targets
  ITK->>ITK: rewrite missing DCMTK:: link-interface entries
  ITK-->>Consumer: exposes corrected ITKIODCMTK dependencies

Loading

_{Reviews (1): Last reviewed commit: "COMP: Repair DCMTK build-tree export ref..." | Re-trigger Greptile}

[greptile-apps]

Include suffixed targets
The repair loop uses the unsuffixed _ITKDCMTK_LIB_NAMES, but this file creates and links DCMTK::${_dcmtk_lib}${DCMTK_LIBRARY_SUFFIX} targets at lines 151-161. When DCMTK_LIBRARY_SUFFIX is non-empty, no DCMTK::dcmdata target exists, so the loop skips every exported DCMTK target and leaves the broken DCMTK::ITK::* references in the build-tree export.

Artifacts

Repro: deterministic suffixed DCMTK repair harness

• Contains supporting evidence from the run (text/x-python; charset=utf-8).

Repro: harness execution log showing skipped repair and remaining broken entry

• Keeps the command output available without making the summary code-heavy.

Repro: command-v output showing CMake and Ninja unavailable

• Keeps the command output available without making the summary code-heavy.

_{Ran code and verified through T-Rex}

[blowekamp]

This solution does not seem quite right to me.

If DCMTK saw ITK's provided libraries as "imported" targets it would not alter the namespace. I tries one way to modify the ITK's third party libraries to be imported target to DCMTK but it did not work. I may look into modifying how DCMTK does the exports.

I have not found this type of issue in searches. I may create a minimal reproducible example and seek some advice on it.

[hjmjohnson]

I may create a minimal reproducible example and seek some advice on it.

@blowekamp See DCMTK/dcmtk#150 for a minimal reproducible example. I am trying to build a forest of tools (ANTs, BRAINSTools, Slicer, SlicerExtensions, ITK-SNAP, .... and may others, and keep running into DCMTK build failures downstream.

[blowekamp]

I may create a minimal reproducible example and seek some advice on it.

@blowekamp See DCMTK/dcmtk#150 for a minimal reproducible example. I am trying to build a forest of tools (ANTs, BRAINSTools, Slicer, SlicerExtensions, ITK-SNAP, .... and may others, and keep running into DCMTK build failures downstream.

That is a good start to the MRE I was thinking. But I was going also going to create a minimal sub-project to replace DCMTK's library and export.

On thing that is atypical in ITK is that the export name space is set as a property:

ITK/CMake/ITKModuleMacros.cmake

Lines 789 to 794 in a66345a

	set_target_properties(
	${_name}
	PROPERTIES
	EXPORT_NAME
	${_export_namespace}${_name}
	)

I am currently looking at example cmake code which export multiple namespace to see how things can be done.

[hjmjohnson]

@blowekamp Thank you for looking into this. If you find a workable solution, please just push over top of this PR, or close this and open a new PR.