[TOC]
This document is intended to provide a user-level guide to GYP. The emphasis here is on how to use GYP to accomplish specific tasks, not on the complete technical language specification. (For that, see the LanguageSpecification.)
The document below starts with some overviews to provide context: an
overview of the structure of a .gyp file itself, an overview of a
typical executable-program target in a .gyp file, an an overview of a
typical library target in a .gyp file.
After the overviews, there are examples of gyp patterns for different
common use cases.
Here is the skeleton of a typical .gyp file in the Chromium tree:
{
'variables': {
.
.
.
},
'includes': [
'../build/common.gypi',
],
'target_defaults': {
.
.
.
},
'targets': [
{
'target_name': 'target_1',
.
.
.
},
{
'target_name': 'target_2',
.
.
.
},
],
'conditions': [
['OS=="linux"', {
'targets': [
{
'target_name': 'linux_target_3',
.
.
.
},
],
}],
['OS=="win"', {
'targets': [
{
'target_name': 'windows_target_4',
.
.
.
},
],
}, { # OS != "win"
'targets': [
{
'target_name': 'non_windows_target_5',
.
.
.
},
}],
],
}
The entire file just contains a Python dictionary. (It’s actually JSON,
with two small Pythonic deviations: comments are introduced with #,
and a , (comma)) is legal after the last element in a list or
dictionary.)
The top-level pieces in the .gyp file are as follows:
'variables': Definitions of variables that can be interpolated and
used in various other parts of the file.
'includes': A list of of other files that will be included in this
file. By convention, included files have the suffix .gypi (gyp
include).
'target_defaults': Settings that will apply to all of the targets
defined in this .gyp file.
'targets': The list of targets for which this .gyp file can
generate builds. Each target is a dictionary that contains settings
describing all the information necessary to build the target.
'conditions': A list of condition specifications that can modify the
contents of the items in the global dictionary defined by this .gyp
file based on the values of different variablwes. As implied by the
above example, the most common use of a conditions section in the
top-level dictionary is to add platform-specific targets to the
targets list.
The most straightforward target is probably a simple executable program.
Here is an example executable target that demonstrates the features
that should cover most simple uses of gyp:
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'msvs_guid': '5ECEC9E5-8F23-47B6-93E0-C3B328B3BE65',
'dependencies': [
'xyzzy',
'../bar/bar.gyp:bar',
],
'defines': [
'DEFINE_FOO',
'DEFINE_A_VALUE=value',
],
'include_dirs': [
'..',
],
'sources': [
'file1.cc',
'file2.cc',
],
'conditions': [
['OS=="linux"', {
'defines': [
'LINUX_DEFINE',
],
'include_dirs': [
'include/linux',
],
}],
['OS=="win"', {
'defines': [
'WINDOWS_SPECIFIC_DEFINE',
],
}, { # OS != "win",
'defines': [
'NON_WINDOWS_DEFINE',
],
}]
],
},
],
}
The top-level settings in the target include:
'target_name': The name by which the target should be known, which
should be unique across all .gyp files. This name will be used as the
project name in the generated Visual Studio solution, as the target name
in the generated XCode configuration, and as the alias for building this
target from the command line of the generated SCons configuration.
'type': Set to executable, logically enough.
'msvs_guid': THIS IS ONLY TRANSITIONAL. This is a hard-coded GUID
values that will be used in the generated Visual Studio solution
file(s). This allows us to check in a chrome.sln file that
interoperates with gyp-generated project files. Once everything in
Chromium is being generated by gyp, it will no longer be important that
the GUIDs stay constant across invocations, and we’ll likely get rid of
these settings,
'dependencies': This lists other targets that this target depends on.
The gyp-generated files will guarantee that the other targets are built
before this target. Any library targets in the dependencies list will
be linked with this target. The various settings (defines,
include_dirs, etc.) listed in the direct_dependent_settings sections
of the targets in this list will be applied to how this target is
built and linked. See the more complete discussion of
direct_dependent_settings, below.
'defines': The C preprocessor definitions that will be passed in on
compilation command lines (using -D or /D options).
'include_dirs': The directories in which included header files live.
These will be passed in on compilation command lines (using -I or /I
options).
'sources': The source files for this target.
'conditions': A block of conditions that will be evaluated to update
the different settings in the target dictionary.
The vast majority of targets are libraries. Here is an example of a library target including the additional features that should cover most needs of libraries:
{
'targets': [
{
'target_name': 'foo',
'type': '<(library)'
'msvs_guid': '5ECEC9E5-8F23-47B6-93E0-C3B328B3BE65',
'dependencies': [
'xyzzy',
'../bar/bar.gyp:bar',
],
'defines': [
'DEFINE_FOO',
'DEFINE_A_VALUE=value',
],
'include_dirs': [
'..',
],
'direct_dependent_settings': {
'defines': [
'DEFINE_FOO',
'DEFINE_ADDITIONAL',
],
'linkflags': [
],
},
'export_dependent_settings': [
'../bar/bar.gyp:bar',
],
'sources': [
'file1.cc',
'file2.cc',
],
'conditions': [
['OS=="linux"', {
'defines': [
'LINUX_DEFINE',
],
'include_dirs': [
'include/linux',
],
],
['OS=="win"', {
'defines': [
'WINDOWS_SPECIFIC_DEFINE',
],
}, { # OS != "win",
'defines': [
'NON_WINDOWS_DEFINE',
],
}]
],
],
}
The possible entries in a library target are largely the same as those
that can be specified for an executable target (defines,
include_dirs, etc.). The differences include:
'type': This should almost always be set to ‘<(library)’, which allows
the user to define at gyp time whether libraries are to be built static
or shared. (On Linux, at least, linking with shared libraries saves
significant link time.) If it’s necessary to pin down the type of
library to be built, the type can be set explicitly to
static_library or shared_library.
'direct_dependent_settings': This defines the settings that will be
applied to other targets that directly depend on this target–that is,
that list this target in their 'dependencies' setting. This is
where you list the defines, include_dirs, cflags and linkflags
that other targets that compile or link against this target need to
build consistently.
'export_dependent_settings': This lists the targets whose
direct_dependent_settings should be “passed on” to other targets that
use (depend on) this target. TODO: expand on this description.
These use cases are intended to cover the most common actions performed by developers using GYP.
Note that these examples are not fully-functioning, self-contained examples (or else they’d be way too long). Each example mostly contains just the keywords and settings relevant to the example, with perhaps a few extra keywords for context. The intent is to try to show the specific pieces you need to pay attention to when doing something. [NOTE: if practical use shows that these examples are confusing without additional context, please add what’s necessary to clarify things.]
There are similar but slightly different patterns for adding a platform-independent source file vs. adding a source file that only builds on some of the supported platforms.
Simplest possible case: You are adding a file(s) that builds on all platforms.
Just add the file(s) to the sources list of the appropriate dictionary
in the targets list:
{
'targets': [
{
'target_name': 'my_target',
'type': 'executable',
'sources': [
'../other/file_1.cc',
'new_file.cc',
'subdir/file3.cc',
],
},
],
},
File path names are relative to the directory in which the .gyp file lives.
Keep the list sorted alphabetically (unless there’s a really, really, really good reason not to).
*_linux.{ext}, *_mac.{ext}, *_posix.{ext} or *_win.{ext}The simplest way to add a platform-specific source file, assuming you’re adding a completely new file and get to name it, is to use one of the following standard suffixes:
_linux (e.g. foo_linux.cc)_mac (e.g. foo_mac.cc)_posix (e.g. foo_posix.cc)_win (e.g. foo_win.cc)Simply add the file to the sources list of the appropriate dict within
the targets list, like you would any other source file.
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'sources': [
'independent.cc',
'specific_win.cc',
],
},
],
},
The Chromium .gyp files all have appropriate conditions entries to
filter out the files that aren’t appropriate for the current platform.
In the above example, the specific_win.cc file will be removed
automatically from the source-list on non-Windows builds.
If your platform-specific file does not contain a
*_{linux,mac,posix,win} substring (or some other pattern that’s
already in the conditions for the target), and you can’t change the
file name, there are two patterns that can be used.
Prefererred: Add the file to the sources list of the appropriate
dictionary within the targets list. Add an appropriate conditions
section to exclude the specific files name:
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'sources': [
'linux_specific.cc',
],
'conditions': [
['OS != "linux"', {
'sources!': [
# Linux-only; exclude on other platforms.
'linux_specific.cc',
]
}[,
],
},
],
},
Despite the duplicate listing, the above is generally preferred because
the sources list contains a useful global list of all sources on all
platforms with consistent sorting on all platforms.
Non-preferred: In some situations, however, it might make sense to
list a platform-specific file only in a conditions section that
specifically includes it in the sources list:
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'sources': [],
['OS == "linux"', {
'sources': [
# Only add to sources list on Linux.
'linux_specific.cc',
]
}],
},
],
},
The above two examples end up generating equivalent builds, with the
small exception that the sources lists will list the files in
different orders. (The first example defines explicitly where
linux_specific.cc appears in the list–perhaps in in the
middle–whereas the second example will always tack it on to the end of
the list.)
Including or excluding files using patterns: There are more
complicated ways to construct a sources list based on patterns. See
TODO below.
An executable program is probably the most straightforward type of target, since all it typically needs is a list of source files, some compiler/linker settings (probably varied by platform), and some library targets on which it depends and which must be used in the final link.
Add a dictionary defining the new executable target to the targets
list in the appropriate .gyp file. Example:
{
'targets': [
{
'target_name': 'new_unit_tests',
'type': 'executable',
'defines': [
'FOO',
],
'include_dirs': [
'..',
],
'dependencies': [
'other_target_in_this_file',
'other_gyp2:target_in_other_gyp2',
],
'sources': [
'new_additional_source.cc',
'new_unit_tests.cc',
],
},
],
}
Add a dictionary defining the new executable target to the targets
list within an appropriate conditions block for the platform. The
conditions block should be a sibling to the top-level targets list:
{
'targets': [
],
'conditions': [
['OS=="win"', {
'targets': [
{
'target_name': 'new_unit_tests',
'type': 'executable',
'defines': [
'FOO',
],
'include_dirs': [
'..',
],
'dependencies': [
'other_target_in_this_file',
'other_gyp2:target_in_other_gyp2',
],
'sources': [
'new_additional_source.cc',
'new_unit_tests.cc',
],
},
],
}],
],
}
There are several different types of settings that can be defined for any given target.
-D or /D flags)New preprocessor definitions are added by the defines setting:
{
'targets': [
{
'target_name': 'existing_target',
'defines': [
'FOO',
'BAR=some_value',
],
},
],
},
These may be specified directly in a target’s settings, as in the above
example, or in a conditions section.
-I or /I flags)New include directories are added by the include_dirs setting:
{
'targets': [
{
'target_name': 'existing_target',
'include_dirs': [
'..',
'include',
],
},
],
},
These may be specified directly in a target’s settings, as in the above
example, or in a conditions section.
Specific compiler flags can be added with the cflags setting:
{
'targets': [
{
'target_name': 'existing_target',
'conditions': [
['OS=="win"', {
'cflags': [
'/WX',
],
}, { # OS != "win"
'cflags': [
'-Werror',
],
}],
],
},
],
},
Because these flags will be specific to the actual compiler involved,
they will almost always be only set within a conditions section.
Setting linker flags is OS-specific. On linux and most non-mac posix
systems, they can be added with the ldflags setting:
{
'targets': [
{
'target_name': 'existing_target',
'conditions': [
['OS=="linux"', {
'ldflags': [
'-pthread',
],
}],
],
},
],
},
Because these flags will be specific to the actual linker involved,
they will almost always be only set within a conditions section.
On OS X, linker settings are set via xcode_settings, on Windows via
msvs_settings.
Any given settings keyword (defines, include_dirs, etc.) has a
corresponding form with a trailing ! (exclamation point) to remove
values from a setting. One useful example of this is to remove the
Linux -Werror flag from the global settings defined in
build/common.gypi:
{
'targets': [
{
'target_name': 'third_party_target',
'conditions': [
['OS=="linux"', {
'cflags!': [
'-Werror',
],
}],
],
},
],
},
GYP has some (relatively limited) support for cross-compiling.
If the variable GYP_CROSSCOMPILE or one of the toolchain-related
variables (like CC_host or CC_target) is set, GYP will think that
you wish to do a cross-compile.
When cross-compiling, each target can be part of a “host” build, a “target” build, or both. By default, the target is assumed to be (only) part of the “target” build. The ‘toolsets’ property can be set on a target to change the default.
A target’s dependencies are assumed to match the build type (so, if A depends on B, by default that means that a target build of A depends on a target build of B). You can explicitly depend on targets across toolchains by specifying “#host” or “#target” in the dependencies list. If GYP is not doing a cross-compile, the “#host” and “#target” will be stripped as needed, so nothing breaks.
TODO: write intro
Add the a dictionary defining the new library target to the targets
list in the appropriate .gyp file. Example:
{
'targets': [
{
'target_name': 'new_library',
'type': '<(library)',
'defines': [
'FOO',
'BAR=some_value',
],
'include_dirs': [
'..',
],
'dependencies': [
'other_target_in_this_file',
'other_gyp2:target_in_other_gyp2',
],
'direct_dependent_settings': {
'include_dirs': '.',
},
'export_dependent_settings': [
'other_target_in_this_file',
],
'sources': [
'new_additional_source.cc',
'new_library.cc',
],
},
],
}
The use of the <(library) variable above should be the default type
setting for most library targets, as it allows the developer to choose,
at gyp time, whether to build with static or shared libraries.
(Building with shared libraries saves a lot of link time on Linux.)
It may be necessary to build a specific library as a fixed type. Is so,
the type field can be hard-wired appropriately. For a static library:
'type': 'static_library',
For a shared library:
'type': 'shared_library',
Add a dictionary defining the new library target to the targets list
within a conditions block that’s a sibling to the top-level targets
list:
{
'targets': [
],
'conditions': [
['OS=="win"', {
'targets': [
{
'target_name': 'new_library',
'type': '<(library)',
'defines': [
'FOO',
'BAR=some_value',
],
'include_dirs': [
'..',
],
'dependencies': [
'other_target_in_this_file',
'other_gyp2:target_in_other_gyp2',
],
'direct_dependent_settings': {
'include_dirs': '.',
},
'export_dependent_settings': [
'other_target_in_this_file',
],
'sources': [
'new_additional_source.cc',
'new_library.cc',
],
},
],
}],
],
}
GYP provides useful primitives for establishing dependencies between targets, which need to be configured in the following situations.
{
'targets': [
{
'target_name': 'foo',
'dependencies': [
'libbar',
],
},
{
'target_name': 'libbar',
'type': '<(library)',
'sources': [
],
},
],
}
Note that if the library target is in a different .gyp file, you have
to specify the path to other .gyp file, relative to this .gyp file’s
directory:
{
'targets': [
{
'target_name': 'foo',
'dependencies': [
'../bar/bar.gyp:libbar',
],
},
],
}
Adding a library often involves updating multiple .gyp files, adding
the target to the approprate .gyp file (possibly a newly-added .gyp
file), and updating targets in the other .gyp files that depend on
(link with) the new library.
We need to build a library (often a third-party library) with specific
preprocessor definitions or command-line flags, and need to ensure that
targets that depend on the library build with the same settings. This
situation is handled by a direct_dependent_settings block:
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'dependencies': [
'libbar',
],
},
{
'target_name': 'libbar',
'type': '<(library)',
'defines': [
'LOCAL_DEFINE_FOR_LIBBAR',
'DEFINE_TO_USE_LIBBAR',
],
'include_dirs': [
'..',
'include/libbar',
],
'direct_dependent_settings': {
'defines': [
'DEFINE_TO_USE_LIBBAR',
],
'include_dirs': [
'include/libbar',
],
},
},
],
}
In the above example, the sources of the foo executable will be
compiled with the options -DDEFINE_TO_USE_LIBBAR -Iinclude/libbar,
because of those settings’ being listed in the
direct_dependent_settings block.
Note that these settings will likely need to be replicated in the
settings for the library target itsef, so that the library will build
with the same options. This does not prevent the target from defining
additional options for its “internal” use when compiling its own source
files. (In the above example, these are the LOCAL_DEFINE_FOR_LIBBAR
define, and the .. entry in the include_dirs list.)
{
'targets': [
{
'target_name': 'foo',
'type': 'executable',
'dependencies': [
'libbar',
],
},
{
'target_name': 'libbar',
'type': '<(library)',
'dependencies': [
'libother'
],
'export_dependent_settings': [
'libother'
],
},
{
'target_name': 'libother',
'type': '<(library)',
'direct_dependent_settings': {
'defines': [
'DEFINE_FOR_LIBOTHER',
],
'include_dirs': [
'include/libother',
],
},
},
],
}
gyp supports building bundles on OS X (.app, .framework, .bundle, etc). Here is an example of this:
{
'target_name': 'test_app',
'product_name': 'Test App Gyp',
'type': 'executable',
'mac_bundle': 1,
'sources': [
'main.m',
'TestAppAppDelegate.h',
'TestAppAppDelegate.m',
],
'mac_bundle_resources': [
'TestApp/English.lproj/InfoPlist.strings',
'TestApp/English.lproj/MainMenu.xib',
],
'link_settings': {
'libraries': [
'$(SDKROOT)/System/Library/Frameworks/Cocoa.framework',
],
},
'xcode_settings': {
'INFOPLIST_FILE': 'TestApp/TestApp-Info.plist',
},
},
The mac_bundle key tells gyp that this target should be a bundle.
executable targets get extension .app by default, shared_library
targets get .framework – but you can change the bundle extensions by
setting product_extension if you want. Files listed in
mac_bundle_resources will be copied to the bundle’s Resource folder
of the bundle. You can also set
process_outputs_as_mac_bundle_resources to 1 in actions and rules to
let the output of actions and rules be added to that folder (similar to
process_outputs_as_sources). If product_name is not set, the bundle
will be named after target_nameas usual.
TODO
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