emcmake doesn't locate installed packages - c++

Question

I'm trying to compile a simple C++ program which uses CGAL to WASM. The problem is that for some reason find_package(CGAL) fails when using emsmake cmake, though it works fine when using cmake for compiling regular executables. I'm pretty new to compiling C++ and working with Emscripten, so this is most likely a noob question.
Running emcmake (notice CGAL warning):
cgal % emcmake cmake .
configure: cmake . -DCMAKE_TOOLCHAIN_FILE=/Users/kitty/Downloads/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/Users/kitty/Downloads/emsdk/node/14.18.2_64bit/bin/node;--experimental-wasm-threads
-- This project requires the CGAL library, and will not be compiled.
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/kitty/Projects/cgal
Running regular cmake (no warning):
cgal % cmake .
-- The C compiler identification is AppleClang 13.1.6.13160021
-- The CXX compiler identification is AppleClang 13.1.6.13160021
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Warning at /usr/local/lib/cmake/CGAL/CGALConfig.cmake:92 (message):
CGAL_DATA_DIR cannot be deduced, set the variable CGAL_DATA_DIR to set the
default value of CGAL::data_file_path()
Call Stack (most recent call first):
CMakeLists.txt:10 (find_package)
-- Using header-only CGAL
-- Targetting Unix Makefiles
-- Using /Library/Developer/CommandLineTools/usr/bin/c++ compiler.
-- DARWIN_VERSION=21
-- Mac Leopard detected
-- Found GMP: /usr/local/lib/libgmp.dylib
-- Found MPFR: /usr/local/lib/libmpfr.dylib
-- Found Boost: /usr/local/lib/cmake/Boost-1.78.0/BoostConfig.cmake (found suitable version "1.78.0", minimum required is "1.48")
-- Boost include dirs: /usr/local/include
-- Boost libraries:
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- Found Boost: /usr/local/lib/cmake/Boost-1.78.0/BoostConfig.cmake (found version "1.78.0")
CMake Warning at /usr/local/lib/cmake/CGAL/CGAL_enable_end_of_configuration_hook.cmake:99 (message):
=======================================================================
CGAL performance notice:
The variable CMAKE_BUILD_TYPE is set to "". For performance reasons, you
should set CMAKE_BUILD_TYPE to "Release".
Set CGAL_DO_NOT_WARN_ABOUT_CMAKE_BUILD_TYPE to TRUE if you want to disable
this warning.
=======================================================================
Call Stack (most recent call first):
CMakeLists.txt:9223372036854775807 (CGAL_run_at_the_end_of_configuration)
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/kitty/Projects/cgal
Running make afterwards produces a working executable.
CMakeLists.txt (for the most part generated using cgal_create_CMakeLists utility):
# Created by the script cgal_create_CMakeLists
# This is the CMake script for compiling a set of CGAL applications.
cmake_minimum_required(VERSION 3.1...3.15)
project( executable )
# CGAL and its components
find_package( CGAL QUIET COMPONENTS )
if ( NOT CGAL_FOUND )
message(STATUS "This project requires the CGAL library, and will not be compiled.")
return()
endif()
# Boost and its components
find_package( Boost REQUIRED )
if ( NOT Boost_FOUND )
message(STATUS "This project requires the Boost library, and will not be compiled.")
return()
endif()
# include for local directory
# include for local package
# Creating entries for target: executable
# ############################
add_executable( executable test.cpp )
add_to_cached_list( CGAL_EXECUTABLE_TARGETS executable )
# Link the executable to CGAL and third-party libraries
target_link_libraries(executable PRIVATE CGAL::CGAL )
# Lines below are commented for now as they are not required for minimal repro
#set(CMAKE_EXECUTABLE_SUFFIX ".wasm")
#set_target_properties(executable PROPERTIES LINK_FLAGS "-s WASM=1 -s EXPORTED_FUNCTIONS='[_main]'")
test.cpp:
#include <iostream>
int main() {
std::cout << "Hello World!";
return 0;
}

Answer 1

In order for emcmake cmake .. to find the CGAL you would need to build that project for wasm and install it into the emscripten sysroot. (normally emscripten/cache/sysroot). Any libraries in /usr/lib or /usr/local/lib are most likely host libraries and therefore not compatible with wasm or emscripten.