Warnings while building shared library through cmake

[anutosh491]

Using emsdk 3.1.45

I am trying to build a shared lib for a the cppinterop library.

The cmake goes like this

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

  target_link_libraries(clangCppInterOp clangInterpreter)
  )

The first 4 lines are inspired by this comment on how to build shared libs through cmake (#15276 (comment) )

Now while building it I see the following warnings/errors (the build is succesful and i can make use of it though)

(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

[anutosh491]

If I see the link.txt I see quite some things that won't be required including (-z,defs and -soname)

/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,--export=__clang_Interpreter_SetValueNoAlloc -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. two fpic's to begin with, I didn't add any.
2. Lot of warnings like -Werror=date-time which I am not sure how they are coming from, again didn't add any.
3. -Wl,-z,defs and -Wl,-soname,libclangCppInterOp.so -o ../libclangCppInterOp.so ... not sure how crucial are these and where are they coming from.

I guess I am just looking for the SIDE_MODULE=1 flag. So yeah lot of unncessary things here.

Any help to figure out how I could clean this up would be really great.

[sbc100]

I believe those flags are all coming from the llvm build system, nothing to do with emscripten per-say.

[anutosh491]

Oops okay, I didn't realize it would work that way !

So we build libclangInterpreter.a (while building llvm i.e clang and lld for wasm using emscripten) and then want to make use of it through
target_link_libraries(clangCppInterOp clangInterpreter)

Still not sure how the flags are being propagated into CppInterOp's build here but yeah I might have to educate myself here.