[BUG] CMake: cannot create ALIAS target "SUNDIALS::KLU" because target "SuiteSparse::KLU" is itself an ALIAS

[dweindl]

Current Behavior:

Configuring sundials with KLU fails with

  -- KLU version: 2.3.4
  -- KLU include: /home/dweindl/src/AMICI-devel/python/sdist/amici/include/suitesparse
  -- KLU library: /home/dweindl/src/AMICI-devel/python/sdist/amici/lib/libklu.a
  -- KLU static:  /home/dweindl/src/AMICI-devel/python/sdist/amici/lib/libklu.a
  CMake Error at cmake/tpl/FindKLU.cmake:40 (add_library):
    add_library cannot create ALIAS target "SUNDIALS::KLU" because target
    "SuiteSparse::KLU" is itself an ALIAS.
  Call Stack (most recent call first):
    cmake/tpl/SundialsKLU.cmake:48 (find_package)
    cmake/SundialsSetupTPLs.cmake:113 (include)
    CMakeLists.txt:186 (include)

Expected Behavior:

Configuring succeeds.

Steps To Reproduce:

• Build SuiteSparse 7.8.2 with BUILD_SHARED_LIBS=OFF
• Set CMAKE_PREFIX_PATH so the SuiteSparse CMake config can be found
• Configure sundials with -DENABLE_KLU=ON (and not setting any KLU_*)

Environment:

• SUNDIALS: 7.1.1
• SuiteSparse: 7.8.2
• OS: Ubuntu 24.04
• CMake: 3.30.3

Anything else:

Here, sundials tries to create an ALIAS target SUNDIALS::KLU for SuiteSparse::KLU:

sundials/cmake/tpl/FindKLU.cmake

Lines 33 to 40 in c28eaa3

	if (NOT (KLU_INCLUDE_DIR OR KLU_LIBRARY_DIR OR KLU_LIBRARY))
	# Prefer the import target from upstream SuiteSparse if it is available
	# and the user didn't point to a specific (different) version.
	find_package(KLU CONFIG)
	if(TARGET SuiteSparse::KLU)
	if(NOT TARGET SUNDIALS::KLU)
	add_library(SUNDIALS::KLU ALIAS SuiteSparse::KLU)

This works as long as SuiteSparse::KLU is not an alias target itself.

However, for a SuiteSparse static-only build, SuiteSparse::KLU is already an ALIAS of SuiteSparse::KLU_static:

https://github.com/DrTimothyAldenDavis/SuiteSparse/blob/c8c3a9de1c8eef54da5ff19fd0bcf7ca6e8bc9de/KLU/Config/KLUConfig.cmake.in#L113-L116

Proposed fix:

Replace

sundials/cmake/tpl/FindKLU.cmake

Line 40 in c28eaa3

add_library(SUNDIALS::KLU ALIAS SuiteSparse::KLU)

by

      get_target_property(klu_aliased_target SuiteSparse::KLU ALIASED_TARGET)
      if (klu_aliased_target)
          add_library(SUNDIALS::KLU ALIAS ${klu_aliased_target})
      else()
          add_library(SUNDIALS::KLU ALIAS SuiteSparse::KLU)
      endif()

[balos1]

Fixed by #582.