[Bug]: Debug flags responsible for CppInterOp's emscripten build

[anutosh491]

Description of bug

Currently this is how CppInterOp's emscripten build is conducted.

  set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS TRUE)
  set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-s SIDE_MODULE=1")
  set(CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS "-s SIDE_MODULE=1")
  set(CMAKE_STRIP FALSE)

  add_llvm_library(clangCppInterOp
    SHARED

    CppInterOp.cpp
    CXCppInterOp.cpp
    DynamicLibraryManager.cpp
    DynamicLibraryManagerSymbol.cpp
    Paths.cpp

    # Additional libraries from Clang and LLD
    LINK_LIBS
    clangInterpreter
  )

The first 4 lines are necessary to build SHARED objects through cmake using emscripten. Check comment (emscripten-core/emscripten#15276 (comment)). This is followed by add_llvm_library (more like a wrapper over add_library and target_link_libraries). We could even do something as simple as

  add_library(clangCppInterOp SHARED
    CppInterOp.cpp
    CXCppInterOp.cpp
    DynamicLibraryManager.cpp
    DynamicLibraryManagerSymbol.cpp
    Paths.cpp
  )

  target_link_libraries(clangCppInterOp clangInterpreter)

What operating system was you using when the bug occured?

MacOS

What is the architechture of the cpu on your system?

ARM

What did you build CppInterOp against?

Clang-repl (LLVM19)

[anutosh491]

But the link.txt generated during the build process is somewhat weird (lot of things might be unwanted )

/Users/anutosh491/work/emsdk/upstream/emscripten/em++ -fPIC -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wcast-qual -fno-strict-aliasing -pedantic -Wno-long-long -Wall -W -Wno-unused-parameter -Wwrite-strings -O3 -DNDEBUG -Wl,-z,defs -s SIDE_MODULE=1 -Wl,-soname,libclangCppInterOp.so -o ../libclangCppInterOp.so @CMakeFiles/clangCppInterOp.dir/objects1.rsp @CMakeFiles/clangCppInterOp.dir/linkLibs.rsp

1. Not sure what adds the two -fPIC flags to begin with
2. Long list of warning related flags. Do we want everything ?

-Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough  -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wcast-qual

3. -Wl,-z,defs and -Wl,-soname

I don't think these are even recognized by Emscripten and Webassembly

I see these warnings at the end while building cppinterop

(xeus-cpp-wasm-build) anutosh491@Anutoshs-MacBook-Air build2 % emmake make -j1
make: make -j1
[ 16%] Linking CXX shared library ../libclangCppInterOp.so
em++: warning: ignoring unsupported linker flag: `-soname` [-Wlinkflags]
wasm-ld: warning: unknown -z value: defs

4. I see -Wl,-soname,libclangCppInterOp.so.19.1 -o ../libclangCppInterOp.so.19.1

Why do we need to generate libclangCppInterOp.so.19.1 along with libclangCppInterOp.so ? I guess only l ibclangCppInterOp.so would suffice.

Rest things mostly look fine but I am not sure what is responsible for these flags being added. Do they come out of Emscripten's toolchain or cmake .... I am not yet sure !

[anutosh491]

Okay I see when we switch to a combination of add_library + target_link_libraries (instead of add_llvm_library) as raised in the issue description, we stop producing the libclangCppInterOp.so.19.1 and only produce libclangCppInterOp.so.

[github-actions]

This issue is stale because it has been open for 90 days with no activity.