Fix MQLib_jll shared library recipe (#7)

Author: bernalde

c_api/README.md

@@ -39,10 +39,26 @@ containing MQLib's random-forest model files, usually the upstream `hhdata`
 directory. If no model files are found, `mqlib_solve_qubo` returns
 `MQLIB_STATUS_HYPERHEURISTIC_DATA_NOT_FOUND`.
 
-## Build Sketch
+## BinaryBuilder Recipe
 
-The exact build recipe belongs in `MQLib_jll`, but a local syntax check against
-an upstream MQLib checkout looks like:
+The `MQLib_jll` build recipe in `jll/build_tarballs.jl` builds the existing
+`MQLib` executable product and a shared library product named
+`libmqlib_c_api`. The library compiles `c_api/src/mqlib_c_api.cpp` with the
+upstream MQLib implementation sources, excluding the upstream executable entry
+point (`src/main.cpp`), and installs this header as `mqlib_c_api.h`.
+
+Downstream Julia code should call the library product exported by `MQLib_jll`,
+for example:
+
+```julia
+ccall((:mqlib_c_abi_version, libmqlib_c_api), Cint, ())
+```
+
+The public ABI is versioned by `MQLIB_C_ABI_VERSION`. Any incompatible change
+to the structs, status codes, or exported functions must bump that value and be
+released through a new `MQLib_jll` build.
+
+A local syntax check against an upstream MQLib checkout looks like:
 
 ```sh
 c++ -std=c++11 \
@@ -52,11 +68,6 @@ c++ -std=c++11 \
   c_api/src/mqlib_c_api.cpp
 ```
 
-When building the shared library, compile `c_api/src/mqlib_c_api.cpp` together
-with the upstream MQLib implementation sources needed by the heuristics. The
-upstream executable entry point (`src/main.cpp`) should not be part of the
-shared-library target.
-
 The small native example in `c_api/examples/solve_qubo.c` demonstrates both an
 explicit QUBO heuristic and the hyperheuristic call shape:
 

jll/build_tarballs.jl

@@ -0,0 +1,100 @@
+# Note that this script can accept some limited command-line arguments. Run
+# `julia build_tarballs.jl --help` to see a usage message.
+using BinaryBuilder, Pkg
+
+name = "MQLib"
+version = v"0.1.1"
+
+# Collection of sources required to complete build.
+sources = [
+    GitSource(
+        "https://github.com/MQLib/MQLib.git",
+        "585496274af5abb0849d0d47e135496b4688680b",
+    ),
+    # Provides the C ABI wrapper that is packaged as libmqlib_c_api.
+    GitSource(
+        "https://github.com/JuliaQUBO/MQLib.jl.git",
+        "8b491876ef44b663e8fd04a48d262d72e73faff7",
+    ),
+]
+
+# Bash recipe for building across all platforms.
+script = raw"""
+cd "${WORKSPACE}/srcdir"
+
+MQLIB_SRC="${WORKSPACE}/srcdir/MQLib"
+MQLIB_C_HEADER="$(find "${WORKSPACE}/srcdir" -path '*/c_api/include/mqlib_c_api.h' -print -quit)"
+MQLIB_JL_SRC="${MQLIB_C_HEADER%/c_api/include/mqlib_c_api.h}"
+
+if [[ ! -f "${MQLIB_JL_SRC}/c_api/src/mqlib_c_api.cpp" ]]; then
+    echo "Could not find MQLib.jl C ABI sources" >&2
+    exit 1
+fi
+
+cd "${MQLIB_SRC}"
+make -j${nproc}
+install -Dvm 0755 bin/MQLib "${bindir}/MQLib${exeext}"
+install -Dvm 0644 \
+    "${MQLIB_JL_SRC}/c_api/include/mqlib_c_api.h" \
+    "${includedir}/mqlib_c_api.h"
+
+mapfile -t MQLIB_LIBRARY_SOURCES < <(find src -name '*.cpp' ! -name main.cpp | sort)
+
+if [[ "${target}" == *-mingw* ]]; then
+    MQLIB_C_API_LIBRARY="${bindir}/libmqlib_c_api.${dlext}"
+    MQLIB_C_API_SHARED_FLAGS=(
+        -shared
+        -Wl,--out-implib,"${libdir}/libmqlib_c_api.dll.a"
+    )
+elif [[ "${target}" == *-apple-darwin* ]]; then
+    MQLIB_C_API_LIBRARY="${libdir}/libmqlib_c_api.${dlext}"
+    MQLIB_C_API_SHARED_FLAGS=(
+        -dynamiclib
+        -Wl,-install_name,@rpath/libmqlib_c_api.${dlext}
+    )
+else
+    MQLIB_C_API_LIBRARY="${libdir}/libmqlib_c_api.${dlext}"
+    MQLIB_C_API_SHARED_FLAGS=(-shared)
+fi
+
+"${CXX}" \
+    -std=c++11 \
+    -O2 \
+    -fPIC \
+    -DMQLIB_C_BUILD_SHARED \
+    -Iinclude \
+    -I"${MQLIB_JL_SRC}/c_api/include" \
+    "${MQLIB_LIBRARY_SOURCES[@]}" \
+    "${MQLIB_JL_SRC}/c_api/src/mqlib_c_api.cpp" \
+    "${MQLIB_C_API_SHARED_FLAGS[@]}" \
+    -o "${MQLIB_C_API_LIBRARY}" \
+    -lm
+"""
+
+# These are the platforms we will build for by default, unless further
+# platforms are passed in on the command line.
+platforms = expand_cxxstring_abis(supported_platforms())
+
+# The products that we will ensure are always built.
+products = [
+    ExecutableProduct("MQLib", :MQLib),
+    LibraryProduct("libmqlib_c_api", :libmqlib_c_api),
+]
+
+# Dependencies that must be installed before this package can be built.
+dependencies = [
+    Dependency("CompilerSupportLibraries_jll"; platforms = filter(!Sys.isapple, platforms)),
+]
+
+# Build the tarballs, and possibly a `build.jl` as well.
+build_tarballs(
+    ARGS,
+    name,
+    version,
+    sources,
+    script,
+    platforms,
+    products,
+    dependencies;
+    julia_compat = "1.6",
+)

test/runtests.jl

@@ -44,6 +44,9 @@ Test.@testset "C ABI contract" begin
     Test.@test isfile(header)
     Test.@test isfile(source)
 
+    recipe = joinpath(root, "jll", "build_tarballs.jl")
+    Test.@test isfile(recipe)
+
     header_text = read(header, String)
     for symbol in (
         "MQLIB_C_ABI_VERSION",
@@ -80,6 +83,18 @@ Test.@testset "C ABI contract" begin
         end
     end
 
+    recipe_text = read(recipe, String)
+    for snippet in (
+        "ExecutableProduct(\"MQLib\", :MQLib)",
+        "LibraryProduct(\"libmqlib_c_api\", :libmqlib_c_api)",
+        "c_api/include/mqlib_c_api.h",
+        "c_api/src/mqlib_c_api.cpp",
+        "! -name main.cpp",
+        "-DMQLIB_C_BUILD_SHARED",
+    )
+        Test.@test occursin(snippet, recipe_text)
+    end
+
     upstream_dir = get(ENV, "MQLIB_UPSTREAM_DIR", "")
     cxx = first_available_tool(["c++", "g++", "clang++"])
     if isempty(upstream_dir) || !isdir(joinpath(upstream_dir, "include"))