manydeps-gmp

This is a demonstration project from the ManyDeps, for the C/C++ GMP library using package managers (vcpkg and conan) on windows/linux.

If you want to learn more about this repo, please read the Medium text Building Cross-platform C++ GMP library with VCPKG, CMake and Bazel: Lessons Learned.

This works fine on Windows Visual Studio 2022 and also Linux (including Windows WSL). For Linux, the classic gmp library is used, but for Windows, the alternative mpir is used (since gmp currently fails to build on Windows in this repo).

Notes for Windows only: Conan is much faster and requires /MD build (GMP works fine). VCPKG is much slower and requires /MT build (and only MPIR works).

Basic setup in both platforms include: CMake and Ninja. Also it is necessary to have vcpkg and conan, for the following scripts to work.

Running the example on vcpkg

Please follow the next steps carefully.

First step: get submodule dependencies

vcpkg is installed as shown in vcpkg.io website, as a git submodule.

To get submodules, please run the following commands:

git submodule update --init --recursive
git pull --recurse-submodules

Check the folder tools/vcpkg to see if vcpkg is present.

Second step: get vcpkg dependencies

On Windows

On Windows Visual Studio, open the Developer Command Prompt and execute:

.\tools\vcpkg\bootstrap-vcpkg.bat
.\script-deps.bat

On Linux (or WSL)

On Linux (or WSL), just run:

./tools/vcpkg/bootstrap-vcpkg.sh 
./script-deps.sh

Common errors

On Linux, sometimes dependencies are not fully available, so please double check:

Latest CMake on Linux

python3 -m pip install --upgrade

Ninja on Linux

apt-get install ninja-build

General build dependencies on Linux

vcpkg requires some packages, such as pkg-config and autoconf:

apt-get install autoconf automake libtool pkg-config

Using CMakePresets for IDE

Update your CMakePresets.json to include the desired toolchain.

vcpkg toolchain

"toolchainFile": "${sourceDir}/deps/vcpkg/scripts/buildsystems/vcpkg.cmake",

Read more on vcpkg integration: https://learn.microsoft.com/pt-br/vcpkg/users/buildsystems/cmake-integration

conan toolchain

Install conan with:

python3 -m pip install conan

Setup toolchain with cmake and conan:

"cacheVariables": {
    "CMAKE_BUILD_TYPE": "Release",
    "CMAKE_TOOLCHAIN_FILE": "build-conan/conan_toolchain.cmake"
},

Discussion and common errors

The vcpkg tries to create some CMake toolchain with PkgConfig, in order to get dependencies. We try to build them as STATIC libraries: libgmp.a (on linux) and gmp.lib (on windows).

This is the expected configuration after vcpkg install:

[cmake]     #  gmp
[cmake]     find_package(PkgConfig REQUIRED)
[cmake]     pkg_check_modules(gmp REQUIRED IMPORTED_TARGET gmp)
[cmake]     target_link_libraries(main PkgConfig::gmp)
[cmake] 
[cmake]     # gmpxx
[cmake]     find_package(PkgConfig REQUIRED)
[cmake]     pkg_check_modules(gmpxx REQUIRED IMPORTED_TARGET gmpxx)
[cmake]     target_link_libraries(main PkgConfig::gmpxx)

However, this failed in both Linux and Windows (in our experiments here), so we need to make some adjustments (A LOT OF ADJUSTMENTS FOR WINDOWS).

Trying to understand the errors

The idea is to load packages locally on build/vcpkg_installed/ folder (generated by vcpkg on our script-deps).

We still could not fully understand why it fails so bad in Windows, but it seems that some files such as gmp.pc are missing! For Linux they exist on build/vcpkg_installed/x64-linux/lib/pkgconfig/ folder.

If you find a better solution, please Let Us Know!

Testing with Bazel

vcpkg install
# will generate local folder vcpkg_installed

bazel run @hedron_compile_commands//:refresh_all
# will generate local compile_commands.json

bazel build ... --config linux

bazel test ... --config windows

Note some important flags on .bazelrc file. On windows, there are two types of .lib library, so we assume here that GMP/MPIR is built with /MT flag, meaning that we need to add static_link_msvcrt configuration on .bazelrc:

• build:windows --cxxopt=/std:c++17 --cxxopt=/MT --linkopt=/NODEFAULTLIB:MSVCRT --features=static_link_msvcrt

Testing with GitHub Actions

Ongoing work...

Generating SBOM with Conan and CycloneDX extension

Conan automatically generates a Software Bill of Materials (SBOM):

conan config install https://github.com/conan-io/conan-extensions.git
conan sbom:cyclonedx --format 1.4_json .

{
  "components": [
    // ...
    {
      "bom-ref": "pkg:conan/gmp@6.3.0?rref=f925bd29cb8f70972507c699d681de85",
      "description": "GMP is a free library for arbitrary precision arithmetic, operating on signed integers, rational numbers, and floating-point numbers.",
      "externalReferences": [
        {
          "type": "website",
          "url": "https://gmplib.org"
        }
      ],
      "licenses": [
        {
          "license": {
            "id": "GPL-2.0"
          }
        },
        {
          "license": {
            "id": "LGPL-3.0"
          }
        }
      ],
      "name": "gmp",
      "purl": "pkg:conan/gmp@6.3.0?rref=f925bd29cb8f70972507c699d681de85",
      "type": "library",
      "version": "6.3.0"
    }
  ],
  "dependencies": [
    // ...
  ],
  "metadata": {
    // ...
  },
  "serialNumber": "urn:uuid:42ecb73d-d67e-41e3-817f-ce68dd582711",
  "version": 1,
  "$schema": "http://cyclonedx.org/schema/bom-1.4.schema.json",
  "bomFormat": "CycloneDX",
  "specVersion": "1.4"
}

License

GPLv3+ License

(... or at your choice)

LGPLv3+ License

License is a combination of:

• GMP (GPL-2.0-or-later OR LGPL-3.0-or-later)