package_info()¶

The package_info() method is the one responsible of defining the information to the consumers of the package, so those consumers can easily and automatically consume this package. The generate() method of the consumers is the place where the information defined in the package_info() will be mapped to the specific build system of the consumer. Then, if we want a package to be consumed by different build systems (like it happens with ConanCenter recipes for the community), it is very important that this information is complete.

Important

This method defines information exclusively for consumers of this package, not for itself. This method executes after the binary has been built and packaged. The information that is consumed in the build should be processed in generate() method.

cpp_info: Library and build information¶

Each package has to specify certain build information for its consumers. This can be done in the cpp_info attribute.

# Binaries to link
self.cpp_info.libs = []  # The libs to link against
self.cpp_info.system_libs = []  # System libs to link against
self.cpp_info.frameworks = []  # OSX frameworks that consumers will link against
self.cpp_info.objects = []  # precompiled objects like .obj .o that consumers will link
# Directories
self.cpp_info.includedirs = ['include']  # Ordered list of include paths
self.cpp_info.libdirs = ['lib']  # Directories where libraries can be found
self.cpp_info.bindirs = ['bin']  # Directories where executables and shared libs can be found
self.cpp_info.resdirs = []  # Directories where resources, data, etc. can be found
self.cpp_info.srcdirs = []  # Directories where sources can be found (debugging, reusing sources)
self.cpp_info.builddirs = []  # Directories where build scripts for consumers can be found
self.cpp_info.frameworkdirs = []  # Directories where OSX frameworks can be found
# Flags
self.cpp_info.defines = []  # preprocessor definitions
self.cpp_info.cflags = []  # pure C flags
self.cpp_info.cxxflags = []  # C++ compilation flags
self.cpp_info.sharedlinkflags = []  # linker flags
self.cpp_info.exelinkflags = []  # linker flags
# Properties
self.cpp_info.set_property("property_name", "property_value")
# Structure
self.cpp_info.components # Dictionary-like structure to define the different components a package may have
self.cpp_info.requires # List of components from requirements that need to be propagated downstream

Binaries to link:

libs: Ordered list of compiled libraries (contained in the package) the consumers should link. Empty by default.
system_libs: Ordered list of system libs (not contained in the package) the consumers should link. Empty by default.
frameworks: Ordered list of OSX frameworks (contained or not in the package), the consumers should link. Empty by default.
objects: Ordered list of precompiled objects (.obj, .o) contained in the package the consumers should link. Empty by default

Directories:

includedirs: List of relative paths (starting from the package root) of directories where headers can be found. By default it is initialized to ['include'], and it is rarely changed.
libdirs: List of relative paths (starting from the package root) of directories in which to find library object binaries (*.lib, *.a, *.so, *.dylib). By default it is initialized to ['lib'], and it is rarely changed.
bindirs: List of relative paths (starting from the package root) of directories in which to find library runtime binaries (like executable Windows .dlls). By default it is initialized to ['bin'], and it is rarely changed.
resdirs: List of relative paths (starting from the package root) of directories in which to find resource files (images, xml, etc). By default it is empty.
srcdirs: List of relative paths (starting from the package root) of directories in which to find sources (like .c, .cpp). By default it is empty. It might be used to store sources (for later debugging of packages, or to reuse those sources building them in other packages too).
builddirs: List of relative paths (starting from package root) of directories that can contain build scripts that could be used by the consumers. Empty by default.
frameworkdirs: List of relative paths (starting from the package root), of directories containing OSX frameworks.

Flags:

defines: Ordered list of preprocessor directives. It is common that the consumers have to specify some sort of defines in some cases, so that including the library headers matches the binaries.
cflags, cxxflags, sharedlinkflags, exelinkflags: List of flags that the consumer should activate for proper behavior. Rarely used.

Properties: - set_property() allows to define some built-in and user general properties to be propagated with the cpp_info model for consumers. They might contain build-system specific information. Some built-in properties are cmake_file_name, cmake_target_name, pkg_config_name, that can define specific behavior for CMakeDeps or PkgConfigDeps generators. For more information about these, read the specific build system integration documentation.

Structure:

components: Dictionary with names as keys and a component object as value to model the different components a package may have: libraries, executables…
requires: Experimental List of components from the requirements this package (and its consumers) should link with. It will be used by generators that add support for components features.

It is common that different configurations will produce different package_info, for example, the library names might change in different OSs, or different system_libs will be used depending on the compiler and OS:

settings = "os", "compiler", "arch", "build_type"
options = {"shared": [True, False]}

def package_info(self):
    if not self.settings.os == "Windows":
        self.cpp_info.libs = ["zmq-static"] if not self.options.shared else ["zmq"]
    else:
        ...

    if not self.options.shared:
        self.cpp_info.defines = ["ZMQ_STATIC"]
    if self.settings.os == "Windows" and self.settings.compiler == "msvc":
        self.cpp_info.system_libs.append("ws2_32")

Properties¶

Any CppInfo object can declare “properties” that can be read by the generators. The value of a property can be of any type. Check each generator reference to see the properties used on it.

def set_property(self, property_name, value)
def get_property(self, property_name):

Example:

def package_info(self):
    self.cpp_info.set_property("cmake_find_mode", "both")

Components¶

If your package is composed by more than one library, it is possible to declare components that allow to define a CppInfo object per each of those libraries and also requirements between them and to components of other packages (the following case is not a real example):

def package_info(self):
    self.cpp_info.components["crypto"].set_property("cmake_file_name", "Crypto")
    self.cpp_info.components["crypto"].libs = ["libcrypto"]
    self.cpp_info.components["crypto"].defines = ["DEFINE_CRYPTO=1"]
    self.cpp_info.components["crypto"].requires = ["zlib::zlib"]  # Depends on all components in zlib package

    self.cpp_info.components["ssl"].set_property("cmake_file_name", "SSL")
    self.cpp_info.components["ssl"].includedirs = ["include/headers_ssl"]
    self.cpp_info.components["ssl"].libs = ["libssl"]
    self.cpp_info.components["ssl"].requires = ["crypto",
                                                "boost::headers"]  # Depends on headers component in boost package

    obj_ext = "obj" if platform.system() == "Windows" else "o"
    self.cpp_info.components["ssl-objs"].objects = [os.path.join("lib", "ssl-object.{}".format(obj_ext))]

Dependencies among components and to components of other requirements can be defined using the requires attribute and the name of the component. The dependency graph for components will be calculated and values will be aggregated in the correct order for each field.

buildenv_info, runenv_info¶

The buildenv_info and runenv_info attributes are Environment objects that allow to define information for the consumers in the form of environment variables. They can use any of the Environment methods to define such information:

settings = "os", "compiler", "arch", "build_type"

def package_info(self):
    self.buildenv_info.define("MYVAR", "1")
    self.buildenv_info.prepend_path("MYPATH", "my/path")
    if self.settings.os == "Android":
        arch = "myarmarch" if self.settings.arch=="armv8" else "otherarch"
        self.buildenv_info.append("MY_ANDROID_ARCH", f"android-{arch})

    self.runenv_info.append_path("MYRUNPATH", "my/run/path")
    if self.settins.os == "Windows":
        self.runenv_info.define_path("MYPKGHOME", "my/home")

Note that these objects are not tied to either regular requires or tool_requires, any package recipe can use both. The difference between buildenv_info and runenv_info is that the former is applied when Conan is building something from source, like in the build() method, while the later would be used when executing something in the “host” context that would need the runtime activated.

Conan VirtualBuildEnv generator will be used by default in consumers, collecting the information from buildenv_info (and some runenv_info from the “build” context) to create the conanbuild environment script, which runs by default in all self.run(cmd, env="conanbuild") calls. The VirtualRunEnv generator will also be used by default in consumers collecting the runenv_info from the “host” context creating the conanrun environment script, which can be explicitly used with self.run(<cmd>, env="conanrun").

Note

Best practices

It is not necessary to add bindirs to the PATH environment variable, this will be automatically done by the consumer VirtualBuildEnv and VirtualRunEnv generators. Likewise, it is not necessary to add includedirs, libdirs or any other dirs to environment variables, as this information will be typically managed by other generators.

conf_info¶

tool_requires packages in the “build” context can transmit some conf configuration to its immediate consumers, with the conf_info attribute. For example, one Conan package packaging the AndroidNDK could do:

def package_info(self):
    self.conf_info.define_path("tools.android:ndk_path", "path/to/ndk/in/package")

conf_info from packages can still be overwritten from profiles values, because user profiles will have higher priority.

Conf.define(name, value)¶

Define a value for the given configuration name.

Parameters:

name – Name of the configuration.
value – Value of the configuration.

def package_info(self):
    # Setting values
    self.conf_info.define("tools.build:verbosity", "verbose")
    self.conf_info.define("tools.system.package_manager:sudo", True)
    self.conf_info.define("tools.microsoft.msbuild:max_cpu_count", 2)
    self.conf_info.define("user.myconf.build:ldflags", ["--flag1", "--flag2"])
    self.conf_info.define("tools.microsoft.msbuildtoolchain:compile_options", {"ExceptionHandling": "Async"})

Conf.append(name, value)¶

Append a value to the given configuration name.

Parameters:

name – Name of the configuration.
value – Value to append.

def package_info(self):
    # Modifying configuration list-like values
    self.conf_info.append("user.myconf.build:ldflags", "--flag3")  # == ["--flag1", "--flag2", "--flag3"]

Conf.prepend(name, value)¶

Prepend a value to the given configuration name.

Parameters:

name – Name of the configuration.
value – Value to prepend.

def package_info(self):
    self.conf_info.prepend("user.myconf.build:ldflags", "--flag0")  # == ["--flag0", "--flag1", "--flag2", "--flag3"]

Conf.update(name, value)¶

Update the value to the given configuration name.

Parameters:

name – Name of the configuration.
value – Value of the configuration.

def package_info(self):
    # Modifying configuration dict-like values
    self.conf_info.update("tools.microsoft.msbuildtoolchain:compile_options", {"ExpandAttributedSource": "false"})

Conf.remove(name, value)¶

Remove a value from the given configuration name.

Parameters:

name – Name of the configuration.
value – Value to remove.

def package_info(self):
    # Remove
    self.conf_info.remove("user.myconf.build:ldflags", "--flag1")  # == ["--flag0", "--flag2", "--flag3"]

Conf.unset(name)¶

Clears the variable, equivalent to a unset or set XXX=

Parameters:: name – Name of the configuration.

def package_info(self):
    # Unset any value
    self.conf_info.unset("tools.microsoft.msbuildtoolchain:compile_options")

It is possible to define configuration in packages that are tool_requires. For example, assuming there is a package that bundles the AndroidNDK, it could define the location of such NDK to the tools.android:ndk_path configuration as:

import os
from conan import ConanFile

class Pkg(ConanFile):
    name = "android_ndk"

    def package_info(self):
        self.conf_info.define("tools.android:ndk_path", os.path.join(self.package_folder, "ndk"))

Note that this only propagates from the immediate, direct tool_requires of a recipe.

Note

Best practices

The package_info() method is not strictly necessary if you have other means of propagating information for consumers. For example, if your package creates xxx-config.cmake files at build time, and they are put in the final package, it might not be necessary to define package_info() at all, and in the consumer side the CMakeDeps would not be necessary either, as CMakeToolchain is able to inject the paths to locate the xxx-config.cmake files inside the packages. This approach can be good for private usage of Conan, albeit some limitations of CMake, like not being able to manage multi-configuration projects (like Visual Studio switching Debug/Release in the IDE, that CMakeDeps can provide), limitations in some cross-build scenarios using packages that are both libraries and build tools (like protobuf, that also CMakeDeps can handle).
Providing a package_info() is very necessary if consumers can use different build systems, like in ConanCenter. In this case, it is necessary a bit of repetition, and coding the package_info() might feel duplicating the package xxx-config.cmake, but automatically extracting the info from CMake is not feasible at this moment.
If you plan to use editables or the local development flow, there’s a need to check the layout() and define the information for self.cpp.build and self.cpp.source.
It is not necessary to add bindirs to the PATH environment variable, this will be automatically done by the consumer VirtualBuildEnv and VirtualRunEnv generators.
The paths defined in package_info() shouldn’t be converted to any specific format (like the one required by Windows subsystems). Instead, it is the responsibility of the consumer to translate these paths to the adequate format.