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zLib Nuget Package

This project builds a zLib Nuget package with static zLib libraries and header files for Win32/x64 platforms.

Visit zLib website for additional information about the zLib project and library documentation:

https://zlib.net/

Package Configuration

This package contains only static libraries for all platforms listed above. There are no dynamic libraries included.

The zLib static libraries from this package will appear within the installation target project after the package is installed. The solution may need to be reloaded to make libraries visible. Both, debug and release libraries will be listed in the project, but only the one appropriate for the currently selected configuration will be included in the build. These libraries may be moved into solution folders after the installation (e.g. lib/Debug and lib/Release).

Note that the zLib library path in this package will be selected as Debug or Release based on whether the selected configuration is designated as a development or as a release configuration via the standard Visual Studio property called UseDebugLibraries. Additional configurations copied from the standard ones will inherit this property.

Do not install this package if your projects use debug configurations without UseDebugLibraries. Note that CMake-generated Visual Studio projects will not emit this property.

See StoneSteps.zLib.VS2022.Static.props and StoneSteps.zLib.VS2022.Static.targets for specific package configuration details and file locations.

The static library is built with the stdcall calling convention.

The non-debug versions of the library are built with NDEBUG defined, so assert calls work as intended for Debug and Release configurations.

Building a Nuget Package

This project can build a Nuget package for zLib either locally or via a GitHub workflow. In each case, following steps are taken.

  • zLib source archive is downloaded from zLib's website and its SHA-256 signature is verified.

  • zLib's Makefile.msc is patched up to build debug libraries using the debug CRT. See the What's Debug CRT section for more details.

  • VS2022 Community Edition is used to build zLib libraries locally and Enterprise Edition to build libraries on GitHub.

  • Build artifacts for all platforms and configurations are collected in staging directories under nuget/build/native/lib.

  • nuget.exe is used to package staged files with the first three version components used as a zLib version and the last version component used as a package revision. See Package Version section for more details.

  • The Nuget package built on GitHub is uploaded to nuget.org. The package built locally is saved in the root project directory.

Package Version

Package Revision

Nuget packages lack package revision and in order to repackage the same upstream software version, such as zLib v1.2.11, the 4th component of the Nuget version is used to track the Nuget package revision.

Nuget package revision is injected outside of the Nuget package configuration, during the package build process, and is not present in the package specification file.

Specifically, nuget.exe is invoked with -Version=1.2.11.123 to build a package with the revision 123.

In cases when the upstream version lacks the patch level version component, .0 is injected to keep the version consistent with the version pattern sequence (e.g. v1.3 is listed in Nuget as v1.3.0).

Version Locations

zLib version is located in a few places in this repository and needs to be changed in all of them for a new version of zLib.

  • nuget/StoneSteps.zLib.VS2022.Static.nuspec (version)
  • devops/make-package.bat (PKG_VER, PKG_REV, ZLIB_FNAME, ZLIB_SHA256, PKG_VER_PATCH)
  • .github/workflows/build-nuget-package.yml (name, PKG_VER, PKG_REV, ZLIB_FNAME, ZLIB_SHA256, PKG_VER_PATCH)

ZLIB_SHA256 ia a SHA-256 checksum of the zLib package file and needs to be changed when a new version of zLib is released.

Verify that the new zLib archive follows the directory name pattern used in the ZLIB_DNAME variable.

In the GitHub workflow YAML, PKG_REV must be reset to 1 (one) every time zLib version is changed. The workflow file must be renamed with the new version in the name. This is necessary because GitHub maintains build numbers per workflow file name.

For local builds package revision is supplied on the command line and should be specified as 1 (one) for a new version of zLib.

When the upstream version lacks the patch component, PKG_VER_PATCH should be uncommented in all locations listed above to construct a full Nuget version. Otherwise it should be commented out.

GitHub Build Number

Build number within the GitHub workflow YAML is maintained in an unconventional way because of the lack of build maturity management between GitHub and Nuget.

For example, using build management systems, such as Artifactory, every build would generate a Nuget package with the same version and package revision for the upcoming release and build numbers would be tracked within the build management system. A build that was successfully tested would be promoted to the production Nuget repository without generating a new build.

Without a build management system, the GitHub workflow in this repository uses the pre-release version as a surrogate build number for builds that do not publish packages to nuget.org, so these builds can be downloaded and tested before the final build is made and published to nuget.org. This approach is not recommended for robust production environments because even though the final published package is built from the exact same source, the build process may still potentially introduce some unknowns into the final package (e.g. build VM was updated).

CMake vs. nmake

zLib may be built with CMake, but it is configured such that using --prefix with cmake --install fails to copy build artifacts into the specified location and instead forces the protected C:\Program Files\ directory to be used. In addition to this, release builds are not configured to generate debug symbols.

Because of the issues above, nmake is used to build zLib libraries, as it is simpler to maintain, compared to patching CMake files. If you would like to build zLib via CMake, following commands may be used to build all configurations.

cd zlib-1.3

cmake -S . -B build\Win32 -A Win32
cmake -S . -B build\x64 -A x64

cmake --build build\Win32 --config Debug
cmake --build build\Win32 --config Release

cmake --build build\x64 --config Debug
cmake --build build\x64 --config Release

The cmake --install command will attempt to install build artifacts into C:\Program Files\, which is not a good place for libraries, even though it is used by CMake as such.

One work-around for this is to use --install-prefix with the initial cmake -S ... commands, but then you need to change build directories to include configuration names because build files generated this way are not configuration-aware when running cmake --install.

Note that CMake builds static libraries with different names, compared to those within this package. If you switch to using libraries built with CMake, you will need to change references to zlib.lib generated by this project to zlibstatic.lib and zlibstaticd.lib, which are generated by CMake.

Building Package Locally

You can build a Nuget package locally with make-package.bat located in devops. This script expects VS2019 Community Edition installed in the default location. If you have other edition of Visual Studio, edit the file to use the correct path to the vcvarsall.bat file.

Run make-package.bat from the repository root directory with a package revision as the first argument. There is no provision to manage build numbers from the command line and other tools should be used for this.

Sample Application (zPipe)

A Visual Studio project is included in this repository under sample-zpipe to test the Nuget package built by this project. This application is copied from zlib-1.2.11/examples and adapted to build as a C++ project.

The original C source of this sample application is subject to zLib's copyright and terms of use.

In order to build zpipe.exe, open Nuget Package manager in the solution and install either the locally-built Nuget package or the one from nuget.org.

zpipe.exe compresses/decompresses standard input/output and can be tested with this pipe:

echo ABC | zpipe | zpipe -d

The output will be ABC in this example, which will be compressed by the first invocation of zpipe.exe and decompressed by the second one.

What's Debug CRT?

Visual C/C++ provides C runtime library (CRT), which comes in several flavors designed for specific purposes. The debug CRT is intended to help identifying various runtime issues early in the development process, such as memory corruption.

Mixing different flavors of the CRT within one application will yield undesired side effects ranging from compiler errors to application crashes.

The patched version of Makefile.msc in this project builds zLib debug and release versions using multi-threaded debug DLL CRT (/MDd) and multi-threaded non-debug DLL CRT (/MD). See this page for additional information about the CRT.

https://docs.microsoft.com/en-us/cpp/c-runtime-library/crt-library-features?view=msvc-160

See Makefile.msc.patch in patches for changes against the zLib source.