ExternalProject¶
External Project Definition¶
- ExternalProject_Add¶
The
ExternalProject_Add()
function creates a custom target to drive download, update/patch, configure, build, install and test steps of an external project:ExternalProject_Add(<name> [<option>...])
The individual steps within the process can be driven independently if required (e.g. for CDash submission) and extra custom steps can be defined, along with the ability to control the step dependencies. The directory structure used for the management of the external project can also be customized. The function supports a large number of options which can be used to tailor the external project behavior.
Directory Options¶
Most of the time, the default directory layout is sufficient. It is largely
an implementation detail that the main project usually doesn't need to
change. In some circumstances, however, control over the directory layout
can be useful or necessary. The directory options are potentially more
useful from the point of view that the main build can use the
ExternalProject_Get_Property()
command to retrieve their values,
thereby allowing the main project to refer to build artifacts of the
external project.
PREFIX <dir>
Root directory for the external project. Unless otherwise noted below, all other directories associated with the external project will be created under here.
TMP_DIR <dir>
Directory in which to store temporary files.
STAMP_DIR <dir>
Directory in which to store the timestamps of each step. Log files from individual steps are also created in here unless overridden by LOG_DIR (see Logging Options below).
LOG_DIR <dir>
New in version 3.14.
Directory in which to store the logs of each step.
DOWNLOAD_DIR <dir>
Directory in which to store downloaded files before unpacking them. This directory is only used by the URL download method, all other download methods use
SOURCE_DIR
directly instead.SOURCE_DIR <dir>
Source directory into which downloaded contents will be unpacked, or for non-URL download methods, the directory in which the repository should be checked out, cloned, etc. If no download method is specified, this must point to an existing directory where the external project has already been unpacked or cloned/checked out.
Note
If a download method is specified, any existing contents of the source directory may be deleted. Only the URL download method checks whether this directory is either missing or empty before initiating the download, stopping with an error if it is not empty. All other download methods silently discard any previous contents of the source directory.
BINARY_DIR <dir>
Specify the build directory location. This option is ignored if
BUILD_IN_SOURCE
is enabled.INSTALL_DIR <dir>
Installation prefix to be placed in the
<INSTALL_DIR>
placeholder. This does not actually configure the external project to install to the given prefix. That must be done by passing appropriate arguments to the external project configuration step, e.g. using<INSTALL_DIR>
.
If any of the above ..._DIR
options are not specified, their defaults
are computed as follows. If the PREFIX
option is given or the
EP_PREFIX
directory property is set, then an external project is built
and installed under the specified prefix:
TMP_DIR = <prefix>/tmp
STAMP_DIR = <prefix>/src/<name>-stamp
DOWNLOAD_DIR = <prefix>/src
SOURCE_DIR = <prefix>/src/<name>
BINARY_DIR = <prefix>/src/<name>-build
INSTALL_DIR = <prefix>
LOG_DIR = <STAMP_DIR>
Otherwise, if the EP_BASE
directory property is set then components
of an external project are stored under the specified base:
TMP_DIR = <base>/tmp/<name>
STAMP_DIR = <base>/Stamp/<name>
DOWNLOAD_DIR = <base>/Download/<name>
SOURCE_DIR = <base>/Source/<name>
BINARY_DIR = <base>/Build/<name>
INSTALL_DIR = <base>/Install/<name>
LOG_DIR = <STAMP_DIR>
If no PREFIX
, EP_PREFIX
, or EP_BASE
is specified, then the
default is to set PREFIX
to <name>-prefix
. Relative paths are
interpreted with respect to CMAKE_CURRENT_BINARY_DIR
at the
point where ExternalProject_Add()
is called.
Download Step Options¶
A download method can be omitted if the SOURCE_DIR
option is used to
point to an existing non-empty directory. Otherwise, one of the download
methods below must be specified (multiple download methods should not be
given) or a custom DOWNLOAD_COMMAND
provided.
DOWNLOAD_COMMAND <cmd>...
Overrides the command used for the download step (
generator expressions
are supported). If this option is specified, all other download options will be ignored. Providing an empty string for<cmd>
effectively disables the download step.
URL¶
URL <url1> [<url2>...]
List of paths and/or URL(s) of the external project's source. When more than one URL is given, they are tried in turn until one succeeds. A URL may be an ordinary path in the local file system (in which case it must be the only URL provided) or any downloadable URL supported by the
file(DOWNLOAD)
command. A local filesystem path may refer to either an existing directory or to an archive file, whereas a URL is expected to point to a file which can be treated as an archive. When an archive is used, it will be unpacked automatically unless theDOWNLOAD_NO_EXTRACT
option is set to prevent it. The archive type is determined by inspecting the actual content rather than using logic based on the file extension.Changed in version 3.7: Multiple URLs are allowed.
URL_HASH <algo>=<hashValue>
Hash of the archive file to be downloaded. The argument should be of the form
<algo>=<hashValue>
wherealgo
can be any of the hashing algorithms supported by thefile()
command. Specifying this option is strongly recommended for URL downloads, as it ensures the integrity of the downloaded content. It is also used as a check for a previously downloaded file, allowing connection to the remote location to be avoided altogether if the local directory already has a file from an earlier download that matches the specified hash.URL_MD5 <md5>
Equivalent to
URL_HASH MD5=<md5>
.DOWNLOAD_NAME <fname>
File name to use for the downloaded file. If not given, the end of the URL is used to determine the file name. This option is rarely needed, the default name is generally suitable and is not normally used outside of code internal to the
ExternalProject
module.DOWNLOAD_EXTRACT_TIMESTAMP <bool>
New in version 3.24.
When specified with a true value, the timestamps of the extracted files will match those in the archive. When false, the timestamps of the extracted files will reflect the time at which the extraction was performed. If the download URL changes, timestamps based off those in the archive can result in dependent targets not being rebuilt when they potentially should have been. Therefore, unless the file timestamps are significant to the project in some way, use a false value for this option. If
DOWNLOAD_EXTRACT_TIMESTAMP
is not given, the default is false. See policyCMP0135
.DOWNLOAD_NO_EXTRACT <bool>
New in version 3.6.
Allows the extraction part of the download step to be disabled by passing a boolean true value for this option. If this option is not given, the downloaded contents will be unpacked automatically if required. If extraction has been disabled, the full path to the downloaded file is available as
<DOWNLOADED_FILE>
in subsequent steps or as the propertyDOWNLOADED_FILE
with theExternalProject_Get_Property()
command.DOWNLOAD_NO_PROGRESS <bool>
Can be used to disable logging the download progress. If this option is not given, download progress messages will be logged.
TIMEOUT <seconds>
Maximum time allowed for file download operations.
INACTIVITY_TIMEOUT <seconds>
New in version 3.19.
Terminate the operation after a period of inactivity.
HTTP_USERNAME <username>
New in version 3.7.
Username for the download operation if authentication is required.
HTTP_PASSWORD <password>
New in version 3.7.
Password for the download operation if authentication is required.
HTTP_HEADER <header1> [<header2>...]
New in version 3.7.
Provides an arbitrary list of HTTP headers for the download operation. This can be useful for accessing content in systems like AWS, etc.
TLS_VERIFY <bool>
Specifies whether certificate verification should be performed for https URLs. If this option is not provided, the default behavior is determined by the
CMAKE_TLS_VERIFY
variable (seefile(DOWNLOAD)
). If that is also not set, certificate verification will not be performed. In situations whereURL_HASH
cannot be provided, this option can be an alternative verification measure.Changed in version 3.6: This option also applies to
git clone
invocations, although the default behavior is different. IfTLS_VERIFY
is not given andCMAKE_TLS_VERIFY
is not set, the behavior will be determined by git's defaults. Normally, thesslVerify
git config setting defaults to true, but the user may have overridden this at a global level.TLS_CAINFO <file>
Specify a custom certificate authority file to use if
TLS_VERIFY
is enabled. If this option is not specified, the value of theCMAKE_TLS_CAINFO
variable will be used instead (seefile(DOWNLOAD)
)NETRC <level>
New in version 3.11.
Specify whether the
.netrc
file is to be used for operation. If this option is not specified, the value of theCMAKE_NETRC
variable will be used instead (seefile(DOWNLOAD)
). Valid levels are:IGNORED
The
.netrc
file is ignored. This is the default.OPTIONAL
The
.netrc
file is optional, and information in the URL is preferred. The file will be scanned to find which ever information is not specified in the URL.REQUIRED
The
.netrc
file is required, and information in the URL is ignored.
NETRC_FILE <file>
New in version 3.11.
Specify an alternative
.netrc
file to the one in your home directory if theNETRC
level isOPTIONAL
orREQUIRED
. If this option is not specified, the value of theCMAKE_NETRC_FILE
variable will be used instead (seefile(DOWNLOAD)
)
New in version 3.1: Added support for tbz2, .tar.xz, .txz, and .7z extensions.
Git¶
NOTE: A git version of 1.6.5 or later is required if this download method is used.
GIT_REPOSITORY <url>
URL of the git repository. Any URL understood by the
git
command may be used.Changed in version 3.27: A relative URL will be resolved based on the parent project's remote, subject to
CMP0150
. See the policy documentation for how the remote is selected, including conditions where the remote selection can fail. Local filesystem remotes should always use absolute paths.GIT_TAG <tag>
Git branch name, tag or commit hash. Note that branch names and tags should generally be specified as remote names (i.e.
origin/myBranch
rather than simplymyBranch
). This ensures that if the remote end has its tag moved or branch rebased or history rewritten, the local clone will still be updated correctly. In general, however, specifying a commit hash should be preferred for a number of reasons:If the local clone already has the commit corresponding to the hash, no
git fetch
needs to be performed to check for changes each time CMake is re-run. This can result in a significant speed up if many external projects are being used.Using a specific git hash ensures that the main project's own history is fully traceable to a specific point in the external project's evolution. If a branch or tag name is used instead, then checking out a specific commit of the main project doesn't necessarily pin the whole build to a specific point in the life of the external project. The lack of such deterministic behavior makes the main project lose traceability and repeatability.
If
GIT_SHALLOW
is enabled thenGIT_TAG
works only with branch names and tags. A commit hash is not allowed.Note that if not provided,
GIT_TAG
defaults tomaster
, not the default Git branch name.GIT_REMOTE_NAME <name>
The optional name of the remote. If this option is not specified, it defaults to
origin
.GIT_SUBMODULES <module>...
Specific git submodules that should also be updated. If this option is not provided, all git submodules will be updated.
Changed in version 3.16: When
CMP0097
is set toNEW
, if this value is set to an empty string then no submodules are initialized or updated.GIT_SUBMODULES_RECURSE <bool>
New in version 3.17.
Specify whether git submodules (if any) should update recursively by passing the
--recursive
flag togit submodule update
. If not specified, the default is on.GIT_SHALLOW <bool>
New in version 3.6.
When this option is enabled, the
git clone
operation will be given the--depth 1
option. This performs a shallow clone, which avoids downloading the whole history and instead retrieves just the commit denoted by theGIT_TAG
option.GIT_PROGRESS <bool>
New in version 3.8.
When enabled, this option instructs the
git clone
operation to report its progress by passing it the--progress
option. Without this option, the clone step for large projects may appear to make the build stall, since nothing will be logged until the clone operation finishes. While this option can be used to provide progress to prevent the appearance of the build having stalled, it may also make the build overly noisy if lots of external projects are used.GIT_CONFIG <option1> [<option2>...]
New in version 3.8.
Specify a list of config options to pass to
git clone
. Each option listed will be transformed into its own--config <option>
on thegit clone
command line, with each option required to be in the formkey=value
.GIT_REMOTE_UPDATE_STRATEGY <strategy>
New in version 3.18.
When
GIT_TAG
refers to a remote branch, this option can be used to specify how the update step behaves. The<strategy>
must be one of the following:CHECKOUT
Ignore the local branch and always checkout the branch specified by
GIT_TAG
.REBASE
Try to rebase the current branch to the one specified by
GIT_TAG
. If there are local uncommitted changes, they will be stashed first and popped again after rebasing. If rebasing or popping stashed changes fail, abort the rebase and halt with an error. WhenGIT_REMOTE_UPDATE_STRATEGY
is not present, this is the default strategy unless the default has been overridden withCMAKE_EP_GIT_REMOTE_UPDATE_STRATEGY
(see below). Note that if the branch specified inGIT_TAG
is different to the upstream branch currently being tracked, it is not safe to perform a rebase. In that situation,REBASE
will silently be treated asCHECKOUT
instead.REBASE_CHECKOUT
Same as
REBASE
except if the rebase fails, an annotated tag will be created at the originalHEAD
position from before the rebase and then checkoutGIT_TAG
just like theCHECKOUT
strategy. The message stored on the annotated tag will give information about what was attempted and the tag name will include a timestamp so that each failed run will add a new tag. This strategy ensures no changes will be lost, but updates should always succeed ifGIT_TAG
refers to a valid ref unless there are uncommitted changes that cannot be popped successfully.
The variable
CMAKE_EP_GIT_REMOTE_UPDATE_STRATEGY
can be set to override the default strategy. This variable should not be set by a project, it is intended for the user to set. It is primarily intended for use in continuous integration scripts to ensure that when history is rewritten on a remote branch, the build doesn't end up with unintended changes or failed builds resulting from conflicts during rebase operations.
Subversion¶
SVN_REPOSITORY <url>
URL of the Subversion repository.
SVN_REVISION -r<rev>
Revision to checkout from the Subversion repository.
SVN_USERNAME <username>
Username for the Subversion checkout and update.
SVN_PASSWORD <password>
Password for the Subversion checkout and update.
SVN_TRUST_CERT <bool>
Specifies whether to trust the Subversion server site certificate. If enabled, the
--trust-server-cert
option is passed to thesvn
checkout and update commands.
Mercurial¶
HG_REPOSITORY <url>
URL of the mercurial repository.
HG_TAG <tag>
Mercurial branch name, tag or commit id.
CVS¶
CVS_REPOSITORY <cvsroot>
CVSROOT of the CVS repository.
CVS_MODULE <mod>
Module to checkout from the CVS repository.
CVS_TAG <tag>
Tag to checkout from the CVS repository.
Update Step Options¶
Whenever CMake is re-run, by default the external project's sources will be
updated if the download method supports updates (e.g. a git repository
would be checked if the GIT_TAG
does not refer to a specific commit).
UPDATE_COMMAND <cmd>...
Overrides the download method's update step with a custom command. The command may use
generator expressions
.UPDATE_DISCONNECTED <bool>
New in version 3.2.
When enabled, this option causes the update step to be skipped (but see below for changed behavior where this is not the case). It does not prevent the download step. The update step can still be added as a step target (see
ExternalProject_Add_StepTargets()
) and called manually. This is useful if you want to allow developers to build the project when disconnected from the network (the network may still be needed for the download step though).Changed in version 3.27: When
UPDATE_DISCONNECTED
is true, the update step will be executed if any details about the update or download step are changed. Furthermore, if using the git download/update method, the update logic will be modified to skip attempts to contact the remote. If theGIT_TAG
mentions a ref that is not known locally, the update step will halt with a fatal error.When this option is present, it is generally advisable to make the value a cache variable under the developer's control rather than hard-coding it. If this option is not present, the default value is taken from the
EP_UPDATE_DISCONNECTED
directory property. If that is also not defined, updates are performed as normal. TheEP_UPDATE_DISCONNECTED
directory property is intended as a convenience for controlling theUPDATE_DISCONNECTED
behavior for an entire section of a project's directory hierarchy and may be a more convenient method of giving developers control over whether or not to perform updates (assuming the project also provides a cache variable or some other convenient method for setting the directory property).This may cause a step target to be created automatically for the
download
step. See policyCMP0114
.
Patch Step Options¶
PATCH_COMMAND <cmd>...
Specifies a custom command to patch the sources after an update. By default, no patch command is defined. Note that it can be quite difficult to define an appropriate patch command that performs robustly, especially for download methods such as git where changing the
GIT_TAG
will not discard changes from a previous patch, but the patch command will be called again after updating to the new tag.
Configure Step Options¶
The configure step is run after the download and update steps. By default, the external project is assumed to be a CMake project, but this can be overridden if required.
CONFIGURE_COMMAND <cmd>...
The default configure command runs CMake with a few options based on the main project. The options added are typically only those needed to use the same generator as the main project, but the
CMAKE_GENERATOR
option can be given to override this. The project is responsible for adding any toolchain details, flags or other settings it wants to reuse from the main project or otherwise specify (seeCMAKE_ARGS
,CMAKE_CACHE_ARGS
andCMAKE_CACHE_DEFAULT_ARGS
below).For non-CMake external projects, the
CONFIGURE_COMMAND
option must be used to override the default configure command (generator expressions
are supported). For projects that require no configure step, specify this option with an empty string as the command to execute.CMAKE_COMMAND /.../cmake
Specify an alternative cmake executable for the configure step (use an absolute path). This is generally not recommended, since it is usually desirable to use the same CMake version throughout the whole build. This option is ignored if a custom configure command has been specified with
CONFIGURE_COMMAND
.CMAKE_GENERATOR <gen>
Override the CMake generator used for the configure step. Without this option, the same generator as the main build will be used. This option is ignored if a custom configure command has been specified with the
CONFIGURE_COMMAND
option.CMAKE_GENERATOR_PLATFORM <platform>
New in version 3.1.
Pass a generator-specific platform name to the CMake command (see
CMAKE_GENERATOR_PLATFORM
). It is an error to provide this option without theCMAKE_GENERATOR
option.CMAKE_GENERATOR_TOOLSET <toolset>
Pass a generator-specific toolset name to the CMake command (see
CMAKE_GENERATOR_TOOLSET
). It is an error to provide this option without theCMAKE_GENERATOR
option.CMAKE_GENERATOR_INSTANCE <instance>
New in version 3.11.
Pass a generator-specific instance selection to the CMake command (see
CMAKE_GENERATOR_INSTANCE
). It is an error to provide this option without theCMAKE_GENERATOR
option.CMAKE_ARGS <arg>...
The specified arguments are passed to the cmake command line. They can be any argument the cmake command understands, not just cache values defined by
-D...
arguments (see alsoCMake Options
).New in version 3.3: Arguments may use
generator expressions
.CMAKE_CACHE_ARGS <arg>...
This is an alternate way of specifying cache variables where command line length issues may become a problem. The arguments are expected to be in the form
-Dvar:STRING=value
, which are then transformed into CMakeset()
commands with theFORCE
option used. Theseset()
commands are written to a pre-load script which is then applied using thecmake -C
command line option.New in version 3.3: Arguments may use
generator expressions
.CMAKE_CACHE_DEFAULT_ARGS <arg>...
New in version 3.2.
This is the same as the
CMAKE_CACHE_ARGS
option except theset()
commands do not include theFORCE
keyword. This means the values act as initial defaults only and will not override any variables already set from a previous run. Use this option with care, as it can lead to different behavior depending on whether the build starts from a fresh build directory or reuses previous build contents.New in version 3.15: If the CMake generator is the
Green Hills MULTI
and not overridden, the original project's settings for the GHS toolset and target system customization cache variables are propagated into the external project.SOURCE_SUBDIR <dir>
New in version 3.7.
When no
CONFIGURE_COMMAND
option is specified, the configure step assumes the external project has aCMakeLists.txt
file at the top of its source tree (i.e. inSOURCE_DIR
). TheSOURCE_SUBDIR
option can be used to point to an alternative directory within the source tree to use as the top of the CMake source tree instead. This must be a relative path and it will be interpreted as being relative toSOURCE_DIR
.New in version 3.14: When
BUILD_IN_SOURCE
option is enabled, theBUILD_COMMAND
is used to point to an alternative directory within the source tree.CONFIGURE_HANDLED_BY_BUILD <bool>
New in version 3.20.
Enabling this option relaxes the dependencies of the configure step on other external projects to order-only. This means the configure step will be executed after its external project dependencies are built but it will not be marked dirty when one of its external project dependencies is rebuilt. This option can be enabled when the build step is smart enough to figure out if the configure step needs to be rerun. CMake and Meson are examples of build systems whose build step is smart enough to know if the configure step needs to be rerun.
Build Step Options¶
If the configure step assumed the external project uses CMake as its build
system, the build step will also. Otherwise, the build step will assume a
Makefile-based build and simply run make
with no arguments as the
default build step. This can be overridden with custom build commands if
required.
If both the main project and the external project use make as their build
tool, the build step of the external project is invoked as a recursive
make using $(MAKE)
. This will communicate some build tool settings
from the main project to the external project. If either the main project
or external project is not using make, no build tool settings will be
passed to the external project other than those established by the
configure step (i.e. running ninja -v
in the main project will not
pass -v
to the external project's build step, even if it also uses
ninja
as its build tool).
BUILD_COMMAND <cmd>...
Overrides the default build command (
generator expressions
are supported). If this option is not given, the default build command will be chosen to integrate with the main build in the most appropriate way (e.g. using recursivemake
for Makefile generators orcmake --build
if the project uses a CMake build). This option can be specified with an empty string as the command to make the build step do nothing.BUILD_IN_SOURCE <bool>
When this option is enabled, the build will be done directly within the external project's source tree. This should generally be avoided, the use of a separate build directory is usually preferred, but it can be useful when the external project assumes an in-source build. The
BINARY_DIR
option should not be specified if building in-source.BUILD_ALWAYS <bool>
Enabling this option forces the build step to always be run. This can be the easiest way to robustly ensure that the external project's own build dependencies are evaluated rather than relying on the default success timestamp-based method. This option is not normally needed unless developers are expected to modify something the external project's build depends on in a way that is not detectable via the step target dependencies (e.g.
SOURCE_DIR
is used without a download method and developers might modify the sources inSOURCE_DIR
).BUILD_BYPRODUCTS <file>...
New in version 3.2.
Specifies files that will be generated by the build command but which might or might not have their modification time updated by subsequent builds. This may also be required to explicitly declare dependencies when using the
Ninja
generator. These ultimately get passed through asBYPRODUCTS
to the build step's own underlying call toadd_custom_command()
, which has additional documentation.BUILD_JOB_SERVER_AWARE <bool>
New in version 3.28.
Specifies that the build step is aware of the GNU Make job server. See the
add_custom_command()
documentation of itsJOB_SERVER_AWARE
option for details. This option is relevant only when an explicitBUILD_COMMAND
is specified.
Install Step Options¶
If the configure step assumed the external project uses CMake as its build
system, the install step will also. Otherwise, the install step will assume
a Makefile-based build and simply run make install
as the default build
step. This can be overridden with custom install commands if required.
INSTALL_COMMAND <cmd>...
The external project's own install step is invoked as part of the main project's build. It is done after the external project's build step and may be before or after the external project's test step (see the
TEST_BEFORE_INSTALL
option below). The external project's install rules are not part of the main project's install rules, so if anything from the external project should be installed as part of the main build, these need to be specified in the main build as additionalinstall()
commands. The default install step builds theinstall
target of the external project, but this can be overridden with a custom command using this option (generator expressions
are supported). Passing an empty string as the<cmd>
makes the install step do nothing.INSTALL_BYPRODUCTS <file>...
New in version 3.26.
Specifies files that will be generated by the install command but which might or might not have their modification time updated by subsequent installs. This may also be required to explicitly declare dependencies when using the
Ninja
generator. These ultimately get passed through asBYPRODUCTS
to the install step's own underlying call toadd_custom_command()
, which has additional documentation.
Note
If the CMAKE_INSTALL_MODE
environment variable is set when the
main project is built, it will only have an effect if the following
conditions are met:
The main project's configure step assumed the external project uses CMake as its build system.
The external project's install command actually runs. Note that due to the way
ExternalProject
may use timestamps internally, if nothing the install step depends on needs to be re-executed, the install command might also not need to run.
Note also that ExternalProject
does not check whether the
CMAKE_INSTALL_MODE
environment variable changes from one run
to another.
Test Step Options¶
The test step is only defined if at least one of the following TEST_...
options are provided.
TEST_COMMAND <cmd>...
Overrides the default test command (
generator expressions
are supported). If this option is not given, the default behavior of the test step is to build the external project's owntest
target. This option can be specified with<cmd>
as an empty string, which allows the test step to still be defined, but it will do nothing. Do not specify any of the otherTEST_...
options if providing an empty string as the test command, but prefer to omit allTEST_...
options altogether if the test step target is not needed.TEST_BEFORE_INSTALL <bool>
When this option is enabled, the test step will be executed before the install step. The default behavior is for the test step to run after the install step.
TEST_AFTER_INSTALL <bool>
This option is mainly useful as a way to indicate that the test step is desired but all default behavior is sufficient. Specifying this option with a boolean true value ensures the test step is defined and that it comes after the install step. If both
TEST_BEFORE_INSTALL
andTEST_AFTER_INSTALL
are enabled, the latter is silently ignored.TEST_EXCLUDE_FROM_MAIN <bool>
New in version 3.2.
If enabled, the main build's default ALL target will not depend on the test step. This can be a useful way of ensuring the test step is defined but only gets invoked when manually requested. This may cause a step target to be created automatically for either the
install
orbuild
step. See policyCMP0114
.
Output Logging Options¶
Each of the following LOG_...
options can be used to wrap the relevant
step in a script to capture its output to files. The log files will be
created in LOG_DIR
if supplied or otherwise the STAMP_DIR
directory with step-specific file names.
LOG_DOWNLOAD <bool>
When enabled, the output of the download step is logged to files.
LOG_UPDATE <bool>
When enabled, the output of the update step is logged to files.
LOG_PATCH <bool>
New in version 3.14.
When enabled, the output of the patch step is logged to files.
LOG_CONFIGURE <bool>
When enabled, the output of the configure step is logged to files.
LOG_BUILD <bool>
When enabled, the output of the build step is logged to files.
LOG_INSTALL <bool>
When enabled, the output of the install step is logged to files.
LOG_TEST <bool>
When enabled, the output of the test step is logged to files.
LOG_MERGED_STDOUTERR <bool>
New in version 3.14.
When enabled, stdout and stderr will be merged for any step whose output is being logged to files.
LOG_OUTPUT_ON_FAILURE <bool>
New in version 3.14.
This option only has an effect if at least one of the other
LOG_<step>
options is enabled. If an error occurs for a step which has logging to file enabled, that step's output will be printed to the console ifLOG_OUTPUT_ON_FAILURE
is set to true. For cases where a large amount of output is recorded, just the end of that output may be printed to the console.
Terminal Access Options¶
New in version 3.4.
Steps can be given direct access to the terminal in some cases. Giving a
step access to the terminal may allow it to receive terminal input if
required, such as for authentication details not provided by other options.
With the Ninja
generator, these options place the steps in the
console
job pool
. Each step can be given access
to the terminal individually via the following options:
USES_TERMINAL_DOWNLOAD <bool>
Give the download step access to the terminal.
USES_TERMINAL_UPDATE <bool>
Give the update step access to the terminal.
USES_TERMINAL_PATCH <bool>
New in version 3.23.
Give the patch step access to the terminal.
USES_TERMINAL_CONFIGURE <bool>
Give the configure step access to the terminal.
USES_TERMINAL_BUILD <bool>
Give the build step access to the terminal.
USES_TERMINAL_INSTALL <bool>
Give the install step access to the terminal.
USES_TERMINAL_TEST <bool>
Give the test step access to the terminal.
Target Options¶
DEPENDS <targets>...
Specify other targets on which the external project depends. The other targets will be brought up to date before any of the external project's steps are executed. Because the external project uses additional custom targets internally for each step, the
DEPENDS
option is the most convenient way to ensure all of those steps depend on the other targets. Simply doingadd_dependencies(<name> <targets>)
will not make any of the steps dependent on<targets>
.EXCLUDE_FROM_ALL <bool>
When enabled, this option excludes the external project from the default ALL target of the main build.
STEP_TARGETS <step-target>...
Generate custom targets for the specified steps. This is required if the steps need to be triggered manually or if they need to be used as dependencies of other targets. If this option is not specified, the default value is taken from the
EP_STEP_TARGETS
directory property. SeeExternalProject_Add_StepTargets()
below for further discussion of the effects of this option.INDEPENDENT_STEP_TARGETS <step-target>...
Deprecated since version 3.19: This is allowed only if policy
CMP0114
is not set toNEW
.Generates custom targets for the specified steps and prevent these targets from having the usual dependencies applied to them. If this option is not specified, the default value is taken from the
EP_INDEPENDENT_STEP_TARGETS
directory property. This option is mostly useful for allowing individual steps to be driven independently, such as for a CDash setup where each step should be initiated and reported individually rather than as one whole build. SeeExternalProject_Add_StepTargets()
below for further discussion of the effects of this option.
Miscellaneous Options¶
LIST_SEPARATOR <sep>
For any of the various
..._COMMAND
options, andCMAKE_ARGS
,ExternalProject
will replace<sep>
with;
in the specified command lines. This can be used to ensure a command has a literal;
in it where direct usage would otherwise be interpreted as argument separators to CMake APIs instead. Note that the separator should be chosen to avoid being confused for non-list-separator usages of the sequence. For example, usingLIST_SEPARATOR
allows for passing list values to CMake cache variables on the command line:ExternalProject_Add(example ... # Download options, etc. LIST_SEPARATOR "," CMAKE_ARGS "-DCMAKE_PREFIX_PATH:STRING=${first_prefix},${second_prefix}" )
COMMAND <cmd>...
Any of the other
..._COMMAND
options can have additional commands appended to them by following them with as manyCOMMAND ...
options as needed (generator expressions
are supported). For example:ExternalProject_Add(example ... # Download options, etc. BUILD_COMMAND ${CMAKE_COMMAND} -E echo "Starting $<CONFIG> build" COMMAND ${CMAKE_COMMAND} --build <BINARY_DIR> --config $<CONFIG> COMMAND ${CMAKE_COMMAND} -E echo "$<CONFIG> build complete" )
It should also be noted that each build step is created via a call to
ExternalProject_Add_Step()
. See that command's documentation for the
automatic substitutions that are supported for some options.
Obtaining Project Properties¶
- ExternalProject_Get_Property¶
The
ExternalProject_Get_Property()
function retrieves external project target properties:ExternalProject_Get_Property(<name> <prop1> [<prop2>...])
The function stores property values in variables of the same name. Property names correspond to the keyword argument names of
ExternalProject_Add()
. For example, the source directory might be retrieved like so:ExternalProject_Get_property(myExtProj SOURCE_DIR) message("Source dir of myExtProj = ${SOURCE_DIR}")
Explicit Step Management¶
The ExternalProject_Add()
function on its own is often sufficient for
incorporating an external project into the main build. Certain scenarios
require additional work to implement desired behavior, such as adding in a
custom step or making steps available as manually triggerable targets. The
ExternalProject_Add_Step()
, ExternalProject_Add_StepTargets()
and
ExternalProject_Add_StepDependencies
functions provide the lower level
control needed to implement such step-level capabilities.
- ExternalProject_Add_Step¶
The
ExternalProject_Add_Step()
function specifies an additional custom step for an external project defined by an earlier call toExternalProject_Add()
:ExternalProject_Add_Step(<name> <step> [<option>...])
<name>
is the same as the name passed to the original call toExternalProject_Add()
. The specified<step>
must not be one of the pre-defined steps (mkdir
,download
,update
,patch
,configure
,build
,install
ortest
). The supported options are:COMMAND <cmd>...
The command line to be executed by this custom step (
generator expressions
are supported). This option can be repeated multiple times to specify multiple commands to be executed in order.COMMENT "<text>..."
Text to be printed when the custom step executes.
DEPENDEES <step>...
Other steps (custom or pre-defined) on which this step depends.
DEPENDERS <step>...
Other steps (custom or pre-defined) that depend on this new custom step.
DEPENDS <file>...
Files on which this custom step depends.
INDEPENDENT <bool>
New in version 3.19.
Specifies whether this step is independent of the external dependencies specified by the
ExternalProject_Add()
'sDEPENDS
option. The default isFALSE
. Steps marked as independent may depend only on other steps marked independent. See policyCMP0114
.Note that this use of the term "independent" refers only to independence from external targets specified by the
DEPENDS
option and is orthogonal to a step's dependencies on other steps.If a step target is created for an independent step by the
ExternalProject_Add()
STEP_TARGETS
option or by theExternalProject_Add_StepTargets()
function, it will not depend on the external targets, but may depend on targets for other steps.BYPRODUCTS <file>...
New in version 3.2.
Files that will be generated by this custom step but which might or might not have their modification time updated by subsequent builds. This may also be required to explicitly declare dependencies when using the
Ninja
generator. This list of files will ultimately be passed through as theBYPRODUCTS
option to theadd_custom_command()
used to implement the custom step internally, which has additional documentation.ALWAYS <bool>
When enabled, this option specifies that the custom step should always be run (i.e. that it is always considered out of date).
JOB_SERVER_AWARE <bool>
New in version 3.28.
Specifies that the custom step is aware of the GNU Make job server. See the
add_custom_command()
documentation of itsJOB_SERVER_AWARE
option for details.EXCLUDE_FROM_MAIN <bool>
When enabled, this option specifies that the external project's main target does not depend on the custom step. This may cause step targets to be created automatically for the steps on which this step depends. See policy
CMP0114
.WORKING_DIRECTORY <dir>
Specifies the working directory to set before running the custom step's command. If this option is not specified, the directory will be the value of the
CMAKE_CURRENT_BINARY_DIR
at the point whereExternalProject_Add_Step()
was called.LOG <bool>
If set, this causes the output from the custom step to be captured to files in the external project's
LOG_DIR
if supplied orSTAMP_DIR
.USES_TERMINAL <bool>
If enabled, this gives the custom step direct access to the terminal if possible.
The command line, comment, working directory and byproducts of every standard and custom step are processed to replace the tokens
<SOURCE_DIR>
,<SOURCE_SUBDIR>
,<BINARY_DIR>
,<INSTALL_DIR>
<TMP_DIR>
,<DOWNLOAD_DIR>
and<DOWNLOADED_FILE>
with their corresponding property values defined in the original call toExternalProject_Add()
.New in version 3.3: Token replacement is extended to byproducts.
New in version 3.11: The
<DOWNLOAD_DIR>
substitution token.
- ExternalProject_Add_StepTargets¶
The
ExternalProject_Add_StepTargets()
function generates targets for the steps listed. The name of each created target will be of the form<name>-<step>
:ExternalProject_Add_StepTargets(<name> <step1> [<step2>...])
Creating a target for a step allows it to be used as a dependency of another target or to be triggered manually. Having targets for specific steps also allows them to be driven independently of each other by specifying targets on build command lines. For example, you may be submitting to a sub-project based dashboard where you want to drive the configure portion of the build, then submit to the dashboard, followed by the build portion, followed by tests. If you invoke a custom target that depends on a step halfway through the step dependency chain, then all the previous steps will also run to ensure everything is up to date.
Internally,
ExternalProject_Add()
callsExternalProject_Add_Step()
to create each step. If anySTEP_TARGETS
were specified, thenExternalProject_Add_StepTargets()
will also be called afterExternalProject_Add_Step()
. Even if a step is not mentioned in theSTEP_TARGETS
option,ExternalProject_Add_StepTargets()
can still be called later to manually define a target for the step.The
STEP_TARGETS
option forExternalProject_Add()
is generally the easiest way to ensure targets are created for specific steps of interest. For custom steps,ExternalProject_Add_StepTargets()
must be called explicitly if a target should also be created for that custom step. An alternative to these two options is to populate theEP_STEP_TARGETS
directory property. It acts as a default for the step target options and can save having to repeatedly specify the same set of step targets when multiple external projects are being defined.New in version 3.19: If
CMP0114
is set toNEW
, step targets are fully responsible for holding the custom commands implementing their steps. The primary target created byExternalProject_Add
depends on the step targets, and the step targets depend on each other. The target-level dependencies match the file-level dependencies used by the custom commands for each step. The targets for steps created withExternalProject_Add_Step()
'sINDEPENDENT
option do not depend on the external targets specified byExternalProject_Add()
'sDEPENDS
option. The predefined stepsmkdir
,download
,update
, andpatch
are independent.If
CMP0114
is notNEW
, the following deprecated behavior is available:A deprecated
NO_DEPENDS
option may be specified immediately after the<name>
and before the first step. If theNO_DEPENDS
option is specified, the step target will not depend on the dependencies of the external project (i.e. on any dependencies of the<name>
custom target created byExternalProject_Add()
). This is usually safe for thedownload
,update
andpatch
steps, since they do not typically require that the dependencies are updated and built. UsingNO_DEPENDS
for any of the other pre-defined steps, however, may break parallel builds. Only useNO_DEPENDS
where it is certain that the named steps genuinely do not have dependencies. For custom steps, consider whether or not the custom commands require the dependencies to be configured, built and installed.The
INDEPENDENT_STEP_TARGETS
option forExternalProject_Add()
, or theEP_INDEPENDENT_STEP_TARGETS
directory property, tells the function to callExternalProject_Add_StepTargets()
internally using theNO_DEPENDS
option for the specified steps.
- ExternalProject_Add_StepDependencies¶
New in version 3.2.
The
ExternalProject_Add_StepDependencies()
function can be used to add dependencies to a step. The dependencies added must be targets CMake already knows about (these can be ordinary executable or library targets, custom targets or even step targets of another external project):ExternalProject_Add_StepDependencies(<name> <step> <target1> [<target2>...])
This function takes care to set both target and file level dependencies and will ensure that parallel builds will not break. It should be used instead of
add_dependencies()
whenever adding a dependency for some of the step targets generated by theExternalProject
module.
Examples¶
The following example shows how to download and build a hypothetical project called FooBar from github:
include(ExternalProject)
ExternalProject_Add(foobar
GIT_REPOSITORY git@github.com:FooCo/FooBar.git
GIT_TAG origin/release/1.2.3
)
For the sake of the example, also define a second hypothetical external project
called SecretSauce, which is downloaded from a web server. Two URLs are given
to take advantage of a faster internal network if available, with a fallback to
a slower external server. The project is a typical Makefile
project with no
configure step, so some of the default commands are overridden. The build is
only required to build the sauce target:
find_program(MAKE_EXE NAMES gmake nmake make)
ExternalProject_Add(secretsauce
URL http://intranet.somecompany.com/artifacts/sauce-2.7.tgz
https://www.somecompany.com/downloads/sauce-2.7.zip
URL_HASH MD5=d41d8cd98f00b204e9800998ecf8427e
CONFIGURE_COMMAND ""
BUILD_COMMAND ${MAKE_EXE} sauce
)
Suppose the build step of secretsauce
requires that foobar
must already
be built. This could be enforced like so:
ExternalProject_Add_StepDependencies(secretsauce build foobar)
Another alternative would be to create a custom target for foobar
's build
step and make secretsauce
depend on that rather than the whole foobar
project. This would mean foobar
only needs to be built, it doesn't need to
run its install or test steps before secretsauce
can be built. The
dependency can also be defined along with the secretsauce
project:
ExternalProject_Add_StepTargets(foobar build)
ExternalProject_Add(secretsauce
URL http://intranet.somecompany.com/artifacts/sauce-2.7.tgz
https://www.somecompany.com/downloads/sauce-2.7.zip
URL_HASH MD5=d41d8cd98f00b204e9800998ecf8427e
CONFIGURE_COMMAND ""
BUILD_COMMAND ${MAKE_EXE} sauce
DEPENDS foobar-build
)
Instead of calling ExternalProject_Add_StepTargets()
, the target could
be defined along with the foobar
project itself:
ExternalProject_Add(foobar
GIT_REPOSITORY git@github.com:FooCo/FooBar.git
GIT_TAG origin/release/1.2.3
STEP_TARGETS build
)
If many external projects should have the same set of step targets, setting a
directory property may be more convenient. The build
step target could be
created automatically by setting the EP_STEP_TARGETS
directory property
before creating the external projects with ExternalProject_Add()
:
set_property(DIRECTORY PROPERTY EP_STEP_TARGETS build)
Lastly, suppose that secretsauce
provides a script called makedoc
which
can be used to generate its own documentation. Further suppose that the script
expects the output directory to be provided as the only parameter and that it
should be run from the secretsauce
source directory. A custom step and a
custom target to trigger the script can be defined like so:
ExternalProject_Add_Step(secretsauce docs
COMMAND <SOURCE_DIR>/makedoc <BINARY_DIR>
WORKING_DIRECTORY <SOURCE_DIR>
COMMENT "Building secretsauce docs"
ALWAYS TRUE
EXCLUDE_FROM_MAIN TRUE
)
ExternalProject_Add_StepTargets(secretsauce docs)
The custom step could then be triggered from the main build like so:
cmake --build . --target secretsauce-docs