Eigen3 fails to find standard math library on MacOS

[rlorigro]

What version of OR-Tools and what language are you using?
Version: https://github.com/google/or-tools/archive/refs/tags/v9.10.tar.gz
Language: C++

Which solver are you using (e.g. CP-SAT, Routing Solver, GLOP, BOP, Gurobi)
Any

What operating system (Linux, Windows, ...) and version?

-- CMAKE_CXX_COMPILER_ID: AppleClang
-- CMAKE_CXX_COMPILER_VERSION: 16.0.0.16000026
-- CMAKE_SYSTEM: Darwin-23.6.0

Apple M1
14.7.2 (23H311)

What did you do?
Steps to reproduce the behavior:
Attempt to build on my system using FetchContent:

    include(FetchContent)
    FetchContent_Declare(
            ortools
            URL https://github.com/google/or-tools/archive/refs/tags/v9.10.tar.gz
    )

    set(BUILD_DEPS ON)
    set(BUILD_DOC OFF)
    set(BUILD_SAMPLES OFF)
    set(BUILD_EXAMPLES OFF)
    set(USE_COINOR OFF)
    set(USE_HIGHS OFF)
    FetchContent_MakeAvailable(ortools)

    include_directories(
            ${ortools_SOURCE_DIR}
            ${ortools_BINARY_DIR}
            ${absl_SOURCE_DIR}
            ${protobuf_SOURCE_DIR}/src
    )

    add_dependencies(sv_merge ortools)

What did you expect to see
No CMake errors

What did you see instead?
Cmake Errors:

CMake Error at build/_deps/eigen3-src/CMakeLists.txt:114 (message):
  Can't link to the standard math library.  Please report to the Eigen
  developers, telling them about your platform.

this is the code that fails:

find_package(StandardMathLibrary)


set(EIGEN_TEST_CUSTOM_LINKER_FLAGS  "" CACHE STRING "Additional linker flags when linking unit tests.")
set(EIGEN_TEST_CUSTOM_CXX_FLAGS     "" CACHE STRING "Additional compiler flags when compiling unit tests.")

set(EIGEN_STANDARD_LIBRARIES_TO_LINK_TO "")

if(NOT STANDARD_MATH_LIBRARY_FOUND)

  message(FATAL_ERROR
    "Can't link to the standard math library. Please report to the Eigen developers, telling them about your platform.")

else()

  if(EIGEN_STANDARD_LIBRARIES_TO_LINK_TO)
    set(EIGEN_STANDARD_LIBRARIES_TO_LINK_TO "${EIGEN_STANDARD_LIBRARIES_TO_LINK_TO} ${STANDARD_MATH_LIBRARY}")
  else()
    set(EIGEN_STANDARD_LIBRARIES_TO_LINK_TO "${STANDARD_MATH_LIBRARY}")
  endif()

endif()

despite CMake finding the library, when prompted manually:

find_library(MATH_LIBRARY m)
if(MATH_LIBRARY)
    message(STATUS "Found math library: ${MATH_LIBRARY}")
else()
    message(FATAL_ERROR "Math library not found")
endif()

yields:

-- Found math library: /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk/usr/lib/libm.tbd

Anything else we should know about your project / environment

I had a long convo with ChatGPT about this and was not able to resolve it, but it gave me this feedback, which may be useful:

Based on the output, we can see the following:

CMake is finding the math library (libm) at the location /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk/usr/lib/libm.tbd, which is a text-based stub (.tbd), a common way that macOS packages system libraries, especially for SDKs.

This libm.tbd is a stub library rather than a fully linked dynamic library (.dylib), and this could explain the confusion or linking issues you're experiencing.

What is a .tbd file?

.tbd (text-based stub) files in macOS are metadata files that tell the linker where to find the actual dynamic libraries (.dylib) at runtime. The fact that it’s a .tbd file indicates that macOS is providing the math library as a stub, which should be resolved at link time, but it may not be resolving correctly in this case.

I also tried a variety of other solutions, like finding the library and then setting some env variables that Eigen CMake uses, to no avail.

[rlorigro]

Nevermind, it seems my cpp libraries are broken after an update