Building libraries on Windows generates DLLs, but not the corresponding import libraries

[acarta]

On Windows, building a shared library from a Julia package using PackageCompiler produces a shared library, but not an associated import library. As such, shared libraries generated by PackageCompiler cannot be linked to other C/C++ code in a straightforward manner.

When using PackageCompiler to compile a package to a shared library on Windows, the output consists of DLLs corresponding to the package itself as well as the Julia-related dependencies (libjulia.dll, libamd.dll, etc.).

As a MWE, I tried compiling the Julia portion of the libcg proof-of-concept (https://github.com/simonbyrne/libcg) using the following code (run from within libcg/CG):

build_dir = "build"
target_dir = joinpath("..", "..", "target")
project_toml = realpath("Project.toml")

PackageCompiler.create_library(".", target_dir;
                            lib_name="cg",
                            precompile_execution_file=[joinpath(build_dir, "generate_precompile.jl")],
                            precompile_statements_file=[joinpath(build_dir, "additional_precompile.jl")],
                            incremental=false,
                            filter_stdlibs=true,
                            header_files = [joinpath(build_dir, "cg.h")],
                            force=true,
)

The output directory looks like this:

───bin
│       julia.exe
│       libamd.dll
│       libatomic-1.dll
│       libblastrampoline.dll
│       libbtf.dll
│       libcamd.dll
│       libccalltest.dll
│       libccolamd.dll
│       libcholmod.dll
│       libcolamd.dll
│       libcurl-4.dll
│       libdSFMT.dll
│       libgcc_s_seh-1.dll
│       libgfortran-5.dll
│       libgit2.dll
│       libgmp-10.dll
│       libgmp.dll
│       libgmpxx-4.dll
│       libgmpxx.dll
│       libgomp-1.dll
│       libjulia-internal.dll
│       libjulia.dll
│       libklu.dll
│       libldl.dll
│       libLLVM.dll
│       libllvmcalltest.dll
│       libLTO.dll
│       libmbedcrypto.dll
│       libmbedtls.dll
│       libmbedx509.dll
│       libmlir_async_runtime.dll
│       libmlir_c_runner_utils.dll
│       libmlir_runner_utils.dll
│       libmlir_test_cblas.dll
│       libmlir_test_cblas_interface.dll
│       libmpfr-6.dll
│       libmpfr.dll
│       libnghttp2-14.dll
│       libopenblas64_.dll
│       libopenlibm.dll
│       libpcre2-16-0.dll
│       libpcre2-16.dll
│       libpcre2-32-0.dll
│       libpcre2-32.dll
│       libpcre2-8-0.dll
│       libpcre2-8.dll
│       libpcre2-posix-2.dll
│       libquadmath-0.dll
│       librbio.dll
│       libRemarks.dll
│       libspqr.dll
│       libssh2.dll
│       libssp-0.dll
│       libstdc++-6.dll
│       libsuitesparseconfig.dll
│       libumfpack.dll
│       libuv-2.dll
│       libwinpthread-1.dll
│       libz.dll
│
└───include
        cg.h
        julia_init.h

However, in order for these DLLs to be implicitly linked to another library/executable (i.e. not using LoadLibrary), there should be corresponding import libraries (.lib or .dll.a); these are not generated by the compilation process initiated by PackageCompiler.

I noticed that PR #614 added tests for create_library, but examining the current state of those tests here, it looks like the test consists mainly of running create_library without checking the output.

Not sure if this is related, but I opened an issue on libcg itself related to the failing build of the C library/executable.

Version Info

julia> versioninfo()
Julia Version 1.7.2
Commit bf53498635 (2022-02-06 15:21 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, skylake-avx512)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS =

[acarta]

As an addendum, there are tools to generate import libraries from DLLs (e.g. lib.exe from MSVC, but there still seem to be problems there, as well. It seemed to me that is a separate issue, and this is the best place to start. However, I can provide more info on that here, if desired, or open a separate issue.

[islent]

I have the same problem when trying to embed julia in a VS C++ project. Without .lib files I got LNK2019 and LNK1120 errors related to unresolved external symbols. I also tried lib.exe and failed. Does anyone have a solution?

[StefanPofahl]

~~I havethe same / similar issue, the compiled project can not be started each MS Window computers.~~ ~~On the machine where I have compiled the project, I am able to run the compiled MyApp.exe,~~ ~~but on another PC, where no Julia is installed, I see:~~

ERROR: Unable to load dependent library C:\Users\joshuaeder\Desktop\Test\../bin/libopenlibm.dll
ERROR: Unable to load dependent library C:\Users\joshuaeder\Desktop\Test\../bin/libgcc_s_seh-1.dll

~~It does not make a difference, if I compile with Julia v1.8.5 or v1.9.0~~ ~~Unfortunately, both missing DLL are already in the "bin" folder ...~~ It was my fault, I had just copied the folder bin. Maybe it can be written more specifically that all three folder must be copied (yes it is written implicitly).