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C++ Driver

API and ABI Versioning

On this page

  • API Versioning
  • ABI Versioning
  • Header File Structure
  • Library Filenames
  • Shared Libraries
  • Shared Libraries (MSVC Only)
  • Static Libraries
  • Static Libraries (MSVC Only)

For brevity, this page may describe properties and features as-if they only apply to the bsoncxx library. Unless stated otherwise, one may assume the properties and features described are similarly applicable to the mongocxx library.

See API Versioning.

See ABI Versioning.

The public header files of the bsoncxx library are organized by ABI namespace:

${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}/
└── bsoncxx/
├── v_noabi/bsoncxx/
│ └── ...
├── v1/bsoncxx/
│ └── ...
├── v2/bsoncxx/
│ └── ...
└── vN/bsoncxx/
└── ...

For forward compatibility, a public header file in an ABI namespace directory vA may include a header file in a newer ABI namespace directory vB, where A < B. Such forward compatibility include directives, when supported, will be explicitly documented. For any given public API entity, we recommend including its corresponding header from the latest ABI namespace directory whenever available.

Important

For backward compatibility, the bsoncxx/v_noabi/ ABI namespace directory is added to include paths such that #include <bsoncxx/example.hpp> is equivalent to #include <bsoncxx/v_noabi/bsoncxx/example.hpp>. Relying on this behavior is discouraged: we recommend explicitly including #include <bsoncxx/v_noabi/bsoncxx/example.hpp> instead.

Note

The stability of an undocumented include directive is not supported.

Package files are installed to subdirectories in ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/. Users are strongly encouraged to use these package files to obtain bsoncxx library header (as well for linking and the setting of compile flags). Manual configuration of include paths to obtain bsoncxx header files is not recommended. Package files are described further below.

In all cases, CMake package config files are the recommended method for importing C++ driver libraries.

The filename and presence of symlinks depends on the platform and toolchain used to build the library, as well as the library type (shared vs. static).

Important

Shared libraries on Windows when configured with the MSVC toolchain on Windows are treated differently due to Windows-specific special considerations. See Shared Libraries (MSVC Only) below.

The "real name" of shared libraries use the following pattern:

lib<basename>.so.<api-version-number>

where:

  • <basename> corresponds to the BSONCXX_OUTPUT_BASENAME CMake configuration variable (MONGOCXX_OUTPUT_BASENAME for the mongocxx library). By default, this is set to bsoncxx and mongocxx. The basename of a static library is suffixed with -static.

  • <api-version-number> is the MAJOR, MINOR, and PATCH version for the given build configuration, corresponding to the BUILD_VERSION CMake configuration variable. (Note: explicitly setting this configuration variable should not be necessary in regular use of the C++ driver.)

  • API version number extensions are not included in the real name (e.g. the -alpha in 1.2.3-alpha).

Examples of expected library real names include:

libbsoncxx.so.1.0.0
libbsoncxx.so.2.3.4

CMake's SOVERSION target property and "namelink" behavior is used to also install symlinks to the library directory consistent with the Linux soname convention. These symlinks include the ABI version number as part of the library soname.

For example, the following lib directory contains the expected library files for a bsoncxx library with API version 1.2.3 and ABI version 10, where a -> b indicates a is a symlink to b:

${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/
├── libbsoncxx.so.1.2.3
├── libbsoncxx.so.10 -> libbsoncxx.so.1.2.3
├── libbsoncxx.so -> libbsoncxx.so.10
├── cmake/bsoncxx-1.2.3/
│ ├── bsoncxx-config.cmake
│ └── ...
└── pkgconfig/
└── libbsoncxx.pc

The name of the CMake package for bsoncxx libraries is controlled by BSONCXX_OUTPUT_BASENAME (MONGOCXX_OUTPUT_BASENAME for mongocxx libraries). They should be imported according to CMake's Config Mode Search Procedure. For example, assuming the C++ driver was installed to a prefix $INSTALLDIR:

# The CMake package may be imported via CMAKE_PREFIX_PATH (recommended)...
cmake -S example -B example-build -D CMAKE_PREFIX_PATH="$INSTALLDIR"
# Or via <PackageName>_ROOT (assuming BSONCXX_OUTPUT_NAME=bsoncxx)...
cmake -S example -B example-build -D bsoncxx_ROOT="$INSTALLDIR"
# Or via ``PATHS`` in the ``find_package()`` command... or etc.
# find_package(bsoncxx CONFIG REQUIRED PATHS "$INSTALLDIR")

Note

The C Driver is a required dependency for the C++ Driver. The CMake package config files for the C Driver may also need to be imported using the same (or similar) approach to satisfy this dependency.

Although the C++ Driver also provides pkg-config files, users are strongly encouraged to use CMake package config files instead.

The name of the pkg-config file for bsoncxx libraries is also controlled by BSONCXX_OUTPUT_NAME and follow the pattern lib<basename>.pc. The PKG_CONFIG_PATH environment variable may need to be used to augment pkg-config's search path, e.g.:

bsoncxx_cflags="$(PKG_CONFIG_PATH="$INSTALLDIR" pkg-config --cflags "libbsoncxx >= 1.2.3")"
bsoncxx_ldflags="$(PKG_CONFIG_PATH="$INSTALLDIR" pkg-config --libs "libbsoncxx >= 1.2.3")"
g++ $bsoncxx_cflags -c example-a.cpp
g++ $bsoncxx_cflags -c example-b.cpp
g++ $bsoncxx_ldflags -o example example-a.o example-b.o

Since version 3.10.0, the shared libraries when built with the MSVC toolchain on Windows (even when the CMake generator is not Visual Studio) use a different naming scheme from other platforms. To restore prior behavior, which is similar to other platforms, set ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES=OFF.

The name of shared libraries (aka the "output name") use the following pattern (file extension excluded):

<basename>-v<abi-version-number>-<abi-tag>

where:

  • <basename> corresponds to the BSONCXX_OUTPUT_BASENAME CMake configuration variable (MONGOCXX_OUTPUT_BASENAME for the mongocxx library). By default, this is set to bsoncxx and mongocxx. The basename of a static library is suffixed with -static.

  • <abi-version-number> corresponds to the current ABI version number.

  • <abi-tag> describes known properties that affect the binary compatibility of the shared library.

The <abi-tag> is a triplet of letters indicating:

  • Build Type

  • mongoc Link Type

  • Polyfill Library

This is followed by a suffix describing the toolset and runtime library used to build the library. The exact contents of the suffix depend on the build configuration.

Examples of expected library filenames (with a brief description of notable features) include:

  • bsoncxx-v_noabi-rhs-x64-v142-md.dll (release build configuration)

  • bsoncxx-v_noabi-dhs-x64-v142-mdd.dll (debug build configuration)

  • bsoncxx-v_noabi-rts-x64-v142-md.dll (link with mongoc static libraries)

  • bsoncxx-v_noabi-rhi-x64-v142-md.dll (bsoncxx as polyfill library)

  • bsoncxx-v_noabi-rhm-x64-v142-md.dll (mnmlstc/core as polyfill library)

  • bsoncxx-v_noabi-rhb-x64-v142-md.dll (Boost as polyfill library)

  • bsoncxx-v1-rhs-x64-v142-md.dll (ABI version number 1)

  • bsoncxx-v2-rhs-x64-v142-md.dll (ABI version number 2)

Note

This example also applies to the companion .lib file.

This naming scheme allows the bsoncxx library to be built and installed with different build configurations (e.g. Debug vs. Release) and different runtime library requirements (e.g. MultiThreadedDLL vs. MultiThreadedDebugDLL) in parallel and without conflict. See references to ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES and related code in the CMake configuration for more details.

For example, the following install prefix directory contains the expected debug and release library files for a bsoncxx library with API version 1.2.3 and ABI version 10 (the bin directory is included to account for .dll files):

${CMAKE_INSTALL_PREFIX}/
├── ${CMAKE_INSTALL_BINDIR}/
│ ├── bsoncxx-v10-dhs-x64-v142-mdd.dll
│ └── bsoncxx-v10-rhs-x64-v142-md.dll
└── ${CMAKE_INSTALL_LIBDIR}/
├── bsoncxx-v10-dhs-x64-v142-mdd.lib
├── bsoncxx-v10-rhs-x64-v142-md.lib
├── cmake/bsoncxx-1.2.3/
│ ├── bsoncxx-config.cmake
│ └── ...
└── pkgconfig/
├── libbsoncxx-v10-dhs-x64-v142-mdd.pc
└── libbsoncxx-v10-rhs-x64-v142-md.pc

The CMake package config files are the same as the regular (non-MSVC) shared library behavior described above.

Note

CMake automatically handles selection of libraries according to build type, but does not enforce build type consistency when only one build type is installed. Installing both Debug and Release configurations on Windows is highly recommended for this reason. (This note only applies to the build type configuration parameter).

The name of the pkg-config file for C++ Driver libraries is the same as that for the regular (non-MSVC) shared library behavior described above. However, when ENABLE_ABI_TAG_IN_PKGCONFIG_FILENAMES=ON, the library output name is used as-if it were the basename for pkg-config files. For example, to obtain flags for the shared library bsoncxx-v_noabi-rhs-x64-v142-md.dll, the pkg-config command may look as follows when ENABLE_ABI_TAG_IN_PKGCONFIG_FILENAMES=OFF (the default):

pkg-config --cflags "libbsoncxx"

or as follows when ENABLE_ABI_TAG_IN_PKGCONFIG_FILENAMES=ON:

pkg-config --cflags "libbsoncxx-v_noabi-rhs-x64-v142-md"

Setting ENABLE_ABI_TAG_IN_PKGCONFIG_FILENAMES=ON is recommended when parallel installation of C++ Driver libraries with different build configurations (e.g. Debug vs. Release) is expected. However, using CMake package config files instead is most recommended.

Static libraries use a simple filename pattern:

lib<basename>-static.a

No API or ABI version information is included in the name of static library files. Shared vs. static library selection for CMake package config files is handled via CMake targets. Shared vs. static library selection for pkg-config files is handled by adding the -static suffix to the library basename, e.g. lib<basename>-static.pc.

For example, the following library directory contains the expected shared and static library files for a bsoncxx library:

${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/
├── libbsoncxx.so.1.2.3
├── libbsoncxx.so.10 -> libbsoncxx.so.1.2.3
├── libbsoncxx.so -> libbsoncxx.so.10
├── libbsoncxx-static.a
├── cmake/bsoncxx-1.2.3/
│ ├── bsoncxx-config.cmake
│ └── ...
└── pkgconfig/
├── libbsoncxx.pc
└── libbsoncxx-static.pc

The name of static libraries use the same pattern as MSVC shared library behavior described above, but uses static as the <abi-version-number> and the library output name as-if it were the basename.

For example, the following install prefix directory contains the expected shared and static library files for a bsoncxx library (the bin directory is included to account for .dll files):

${CMAKE_INSTALL_PREFIX}/
├── ${CMAKE_INSTALL_BINDIR}/
│ └── bsoncxx-v10-rhs-x64-v142-md.dll
└── ${CMAKE_INSTALL_LIBDIR}/
├── bsoncxx-v10-rhs-x64-v142-md.lib
├── bsoncxx-static-dhs-x64-v142-mdd.lib
├── cmake/bsoncxx-1.2.3/
│ ├── bsoncxx-config.cmake
│ └── ...
└── pkgconfig/
├── libbsoncxx-v10-rhs-x64-v142-md.pc
└── libbsoncxx-static-rhs-x64-v142-md.pc

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