Generate wasm file using emscripten

Question

I want to compile SealPIR library using emscripten to generate a wasm file. When using this command: emcmake cmake .

I get this error:

CMake Error at CMakeLists.txt:19 (find_package):
  By not providing "FindSEAL.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "SEAL", but
  CMake did not find one.

  Could not find a package configuration file provided by "SEAL" (requested
  version 3.2.0) with any of the following names:

    SEALConfig.cmake
    seal-config.cmake

  Add the installation prefix of "SEAL" to CMAKE_PREFIX_PATH or set
  "SEAL_DIR" to a directory containing one of the above files.  If "SEAL"
  provides a separate development package or SDK, be sure it has been
  installed.


-- Configuring incomplete, errors occurred!
See also "/home/Zied/webassembly/SealPIR/CMakeFiles/CMakeOutput.log".
emcmake: error: 'cmake . -DCMAKE_TOOLCHAIN_FILE=/home/Zied/webassembly/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR="/home/Zied/webassembly/emsdk/node/14.15.5_64bit/bin/node"' failed (1)  

SEAL is correctly installed. when i run the same command without emcmake it works just fine. This is my CMakeList

cmake_minimum_required(VERSION 3.10)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

project(SealPIR VERSION 2.1 LANGUAGES CXX)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin)

add_executable(main 
    main.cpp
)

add_library(sealpir STATIC
  pir.cpp
  pir_client.cpp
  pir_server.cpp
)

find_package(SEAL 3.2.0 EXACT REQUIRED)

target_link_libraries(main sealpir SEAL::seal)

Answer 1

When using a toolchain file for cross compiling, CMake will by default disable system libraries. It won't search into any directory to avoid finding files that is not compatible with the target system.

You think you didn't used a toolchain file? Think again! emcmake hides that from you. Look carefully at the error output.

Here you compiled the SEAL library, but you installed it in the default path, which is /usr/local.

We can tell CMake to explicitly search there, but I wouldn't recommend, but you can try if it works:

emcmake cmake . -CMAKE_PREFIX_PATH=/usr/local

The proper solution would be to create a directory with all the emscripten libraries in it:

# In the SEAL build directory
emcmake cmake .. -DCMAKE_INSTALL_PREFIX=/home/anblic/webassembly/install

Then after installing the libraries in that directory, you can set the prefix path in the same directory as the install path:

# Assuming you're in a build/ subdirectory
emcmake cmake .. -DCMAKE_PREFIX_PATH=/home/anblic/webassembly/install