Manpages

NAME

cmake-file-api - CMake File-Based API

INTRODUCTION

CMake provides a file-based API that clients may use to get semantic information about the buildsystems CMake generates. Clients may use the API by writing query files to a specific location in a build tree to request zero or more Object Kinds. When CMake generates the buildsystem in that build tree it will read the query files and write reply files for the client to read.

The file-based API uses a <build>/.cmake/api/ directory at the top of a build tree. The API is versioned to support changes to the layout of files within the API directory. API file layout versioning is orthogonal to the versioning of Object Kinds used in replies. This version of CMake supports only one API version, API v1.

API V1

API v1 is housed in the <build>/.cmake/api/v1/ directory. It has the following subdirectories:

Clients may look for and read a reply index file at any time. Clients may optionally create the reply/ directory at any time and monitor it for the appearance of a new reply index file.

v1 Shared Stateless Query Files
Shared stateless query files allow clients to share requests for major versions of the Object Kinds and get all requested versions recognized by the CMake that runs.

Clients may create shared requests by creating empty files in the v1/query/ directory. The form is:

<build>/.cmake/api/v1/query/<kind>-v<major>

where <kind> is one of the Object Kinds, -v is literal, and <major> is the major version number.

Files of this form are stateless shared queries not owned by any specific client. Once created they should not be removed without external client coordination or human intervention.

v1 Client Stateless Query Files
Client stateless query files allow clients to create owned requests for major versions of the Object Kinds and get all requested versions recognized by the CMake that runs.

Clients may create owned requests by creating empty files in client-specific query subdirectories. The form is:

<build>/.cmake/api/v1/query/client-<client>/<kind>-v<major>

where client- is literal, <client> is a string uniquely identifying the client, <kind> is one of the Object Kinds, -v is literal, and <major> is the major version number. Each client must choose a unique <client> identifier via its own means.

Files of this form are stateless queries owned by the client <client>. The owning client may remove them at any time.

v1 Client Stateful Query Files
Stateful query files allow clients to request a list of versions of each of the Object Kinds and get only the most recent version recognized by the CMake that runs.

Clients may create owned stateful queries by creating query.json files in client-specific query subdirectories. The form is:

<build>/.cmake/api/v1/query/client-<client>/query.json

where client- is literal, <client> is a string uniquely identifying the client, and query.json is literal. Each client must choose a unique <client> identifier via its own means.

query.json files are stateful queries owned by the client <client>. The owning client may update or remove them at any time. When a given client installation is updated it may then update the stateful query it writes to build trees to request newer object versions. This can be used to avoid asking CMake to generate multiple object versions unnecessarily.

A query.json file must contain a JSON object:

{
  "requests": [
    { "kind": "<kind>" , "version": 1 },
    { "kind": "<kind>" , "version": { "major": 1, "minor": 2 } },
    { "kind": "<kind>" , "version": [2, 1] },
    { "kind": "<kind>" , "version": [2, { "major": 1, "minor": 2 }] },
    { "kind": "<kind>" , "version": 1, "client": {} },
    { "kind": "..." }
  ],
  "client": {}
}

The members are:
requests

A JSON array containing zero or more requests. Each request is a JSON object with members:

version

Indicates the version(s) of the object kind that the client understands. Versions have major and minor components following semantic version conventions. The value must be

Optional member reserved for use by the client. This value is preserved in the reply written for the client in the v1 Reply Index File but is otherwise ignored. Clients may use this to pass custom information with a request through to its reply.

For each requested object kind CMake will choose the first version that it recognizes for that kind among those listed in the request. The response will use the selected major version with the highest minor version known to the running CMake for that major version. Therefore clients should list all supported major versions in preferred order along with the minimal minor version required for each major version.

Other query.json top-level members are reserved for future use. If present they are ignored for forward compatibility.

v1 Reply Index File
CMake writes an index-*.json file to the v1/reply/ directory whenever it runs to generate a build system. Clients must read the reply index file first and may read other v1 Reply Files only by following references. The form of the reply index file name is:

<build>/.cmake/api/v1/reply/index-<unspecified>.json

where index- is literal and <unspecified> is an unspecified name selected by CMake. Whenever a new index file is generated it is given a new name and any old one is deleted. During the short time between these steps there may be multiple index files present; the one with the largest name in lexicographic order is the current index file.

The reply index file contains a JSON object:

{
  "cmake": {
    "version": {
      "major": 3, "minor": 14, "patch": 0, "suffix": "",
      "string": "3.14.0", "isDirty": false
    },
    "paths": {
      "cmake": "/prefix/bin/cmake",
      "ctest": "/prefix/bin/ctest",
      "cpack": "/prefix/bin/cpack",
      "root": "/prefix/share/cmake-3.14"
    },
    "generator": {
      "multiConfig": false,
      "name": "Unix Makefiles"
    }
  },
  "objects": [
    { "kind": "<kind>",
      "version": { "major": 1, "minor": 0 },
      "jsonFile": "<file>" },
    { "...": "..." }
  ],
  "reply": {
    "<kind>-v<major>": { "kind": "<kind>",
                         "version": { "major": 1, "minor": 0 },
                         "jsonFile": "<file>" },
    "<unknown>": { "error": "unknown query file" },
    "...": {},
    "client-<client>": {
      "<kind>-v<major>": { "kind": "<kind>",
                           "version": { "major": 1, "minor": 0 },
                           "jsonFile": "<file>" },
      "<unknown>": { "error": "unknown query file" },
      "...": {},
      "query.json": {
        "requests": [ {}, {}, {} ],
        "responses": [
          { "kind": "<kind>",
            "version": { "major": 1, "minor": 0 },
            "jsonFile": "<file>" },
          { "error": "unknown query file" },
          { "...": {} }
        ],
        "client": {}
      }
    }
  }
}

The members are:

version

A JSON object specifying the version of CMake with members:
major, minor, patch

Integer values specifying the major, minor, and patch version components.

isDirty

A boolean indicating whether the version was built from a version controlled source tree with local modifications.

generator

A JSON object describing the CMake generator used for the build. It has members:
multiConfig

A boolean specifying whether the generator supports multiple output configurations.

platform

If the generator supports CMAKE_GENERATOR_PLATFORM, this is a string specifying the generator platform name.

objects

A JSON array listing all versions of all Object Kinds generated as part of the reply. Each array entry is a v1 Reply File Reference.

<kind>-v<major>

A member of this form appears for each of the v1 Shared Stateless Query Files that CMake recognized as a request for object kind <kind> with major version <major>. The value is a v1 Reply File Reference to the corresponding reply file for that object kind and version.

<unknown>

A member of this form appears for each of the v1 Shared Stateless Query Files that CMake did not recognize. The value is a JSON object with a single error member containing a string with an error message indicating that the query file is unknown.

client-<client>

A member of this form appears for each client-owned directory holding v1 Client Stateless Query Files. The value is a JSON object mirroring the content of the query/client-<client>/ directory. The members are of the form:
<kind>-v<major>

A member of this form appears for each of the v1 Client Stateless Query Files that CMake recognized as a request for object kind <kind> with major version <major>. The value is a v1 Reply File Reference to the corresponding reply file for that object kind and version.

<unknown>

A member of this form appears for each of the v1 Client Stateless Query Files that CMake did not recognize. The value is a JSON object with a single error member containing a string with an error message indicating that the query file is unknown.

query.json

This member appears for clients using v1 Client Stateful Query Files. If the query.json file failed to read or parse as a JSON object, this member is a JSON object with a single error member containing a string with an error message. Otherwise, this member is a JSON object mirroring the content of the query.json file. The members are:

requests

A copy of the query.json file requests member, if it exists.

responses

If the query.json file requests member is missing or invalid, this member is a JSON object with a single error member containing a string with an error message. Otherwise, this member contains a JSON array with a response for each entry of the requests array, in the same order. Each response is

After reading the reply index file, clients may read the other v1 Reply Files it references.

v1 Reply File Reference
The reply index file represents each reference to another reply file using a JSON object with members:

version

A JSON object with members major and minor specifying integer version components of the object kind.

jsonFile

A JSON string specifying a path relative to the reply index file to another JSON file containing the object.

v1 Reply Files
Reply files containing specific Object Kinds are written by CMake. The names of these files are unspecified and must not be interpreted by clients. Clients must first read the v1 Reply Index File and and follow references to the names of the desired response objects.

Reply files (including the index file) will never be replaced by files of the same name but different content. This allows a client to read the files concurrently with a running CMake that may generate a new reply. However, after generating a new reply CMake will attempt to remove reply files from previous runs that it did not just write. If a client attempts to read a reply file referenced by the index but finds the file missing, that means a concurrent CMake has generated a new reply. The client may simply start again by reading the new reply index file.

OBJECT KINDS

The CMake file-based API reports semantic information about the build system using the following kinds of JSON objects. Each kind of object is versioned independently using semantic versioning with major and minor components. Every kind of object has the form:

{
  "kind": "<kind>",
  "version": { "major": 1, "minor": 0 },
  "...": {}
}

The kind member is a string specifying the object kind name. The version member is a JSON object with major and minor members specifying integer components of the object kind’s version. Additional top-level members are specific to each object kind.

Object Kind “codemodel”
The codemodel object kind describes the build system structure as modeled by CMake.

There is only one codemodel object major version, version 2. Version 1 does not exist to avoid confusion with that from cmake-server(7) mode.

“codemodel” version 2
codemodel object version 2 is a JSON object:

{
  "kind": "codemodel",
  "version": { "major": 2, "minor": 1 },
  "paths": {
    "source": "/path/to/top-level-source-dir",
    "build": "/path/to/top-level-build-dir"
  },
  "configurations": [
    {
      "name": "Debug",
      "directories": [
        {
          "source": ".",
          "build": ".",
          "childIndexes": [ 1 ],
          "projectIndex": 0,
          "targetIndexes": [ 0 ],
          "hasInstallRule": true,
          "minimumCMakeVersion": {
            "string": "3.14"
          }
        },
        {
          "source": "sub",
          "build": "sub",
          "parentIndex": 0,
          "projectIndex": 0,
          "targetIndexes": [ 1 ],
          "minimumCMakeVersion": {
            "string": "3.14"
          }
        }
      ],
      "projects": [
        {
          "name": "MyProject",
          "directoryIndexes": [ 0, 1 ],
          "targetIndexes": [ 0, 1 ]
        }
      ],
      "targets": [
        {
          "name": "MyExecutable",
          "directoryIndex": 0,
          "projectIndex": 0,
          "jsonFile": "<file>"
        },
        {
          "name": "MyLibrary",
          "directoryIndex": 1,
          "projectIndex": 0,
          "jsonFile": "<file>"
        }
      ]
    }
  ]
}

The members specific to codemodel objects are:

source

configurations

A JSON array of entries corresponding to available build configurations. On single-configuration generators there is one entry for the value of the CMAKE_BUILD_TYPE variable. For multi-configuration generators there is an entry for each configuration listed in the CMAKE_CONFIGURATION_TYPES variable. Each entry is a JSON object containing members:

directories

A JSON array of entries each corresponding to a build system directory whose source directory contains a CMakeLists.txt file. The first entry corresponds to the top-level directory. Each entry is a JSON object containing members:

parentIndex

Optional member that is present when the directory is not top-level. The value is an unsigned integer 0-based index of another entry in the main directories array that corresponds to the parent directory that added this directory as a subdirectory.

childIndexes

Optional member that is present when the directory has subdirectories. The value is a JSON array of entries corresponding to child directories created by the add_subdirectory() or subdirs() command. Each entry is an unsigned integer 0-based index of another entry in the main directories array.

projectIndex

An unsigned integer 0-based index into the main projects array indicating the build system project to which the this directory belongs.

targetIndexes

Optional member that is present when the directory itself has targets, excluding those belonging to subdirectories. The value is a JSON array of entries corresponding to the targets. Each entry is an unsigned integer 0-based index into the main targets array.

minimumCMakeVersion

Optional member present when a minimum required version of CMake is known for the directory. This is the <min> version given to the most local call to the cmake_minimum_required(VERSION) command in the directory itself or one of its ancestors. The value is a JSON object with one member:

<major>.<minor>[.<patch>[.<tweak>]][<suffix>]

Each component is an unsigned integer and the suffix may be an arbitrary string.

hasInstallRule

Optional member that is present with boolean value true when the directory or one of its subdirectories contains any install() rules, i.e. whether a make install or equivalent rule is available.

projects

A JSON array of entries corresponding to the top-level project and sub-projects defined in the build system. Each (sub-)project corresponds to a source directory whose CMakeLists.txt file calls the project() command with a project name different from its parent directory. The first entry corresponds to the top-level project.

Each entry is a JSON object containing members:

parentIndex

Optional member that is present when the project is not top-level. The value is an unsigned integer 0-based index of another entry in the main projects array that corresponds to the parent project that added this project as a sub-project.

childIndexes

Optional member that is present when the project has sub-projects. The value is a JSON array of entries corresponding to the sub-projects. Each entry is an unsigned integer 0-based index of another entry in the main projects array.

directoryIndexes

A JSON array of entries corresponding to build system directories that are part of the project. The first entry corresponds to the top-level directory of the project. Each entry is an unsigned integer 0-based index into the main directories array.

targetIndexes

Optional member that is present when the project itself has targets, excluding those belonging to sub-projects. The value is a JSON array of entries corresponding to the targets. Each entry is an unsigned integer 0-based index into the main targets array.

targets

A JSON array of entries corresponding to the build system targets. Such targets are created by calls to add_executable(), add_library(), and add_custom_target(), excluding imported targets and interface libraries (which do not generate any build rules). Each entry is a JSON object containing members:

directoryIndex

An unsigned integer 0-based index into the main directories array indicating the build system directory in which the target is defined.

projectIndex

An unsigned integer 0-based index into the main projects array indicating the build system project in which the target is defined.

jsonFile

A JSON string specifying a path relative to the codemodel file to another JSON file containing a “codemodel” version 2 “target” object.

“codemodel” version 2 “target” object
A codemodel “target” object is referenced by a “codemodel” version 2 object’s targets array. Each “target” object is a JSON object with members:

backtrace

Optional member that is present when a CMake language backtrace to the command in the source code that created the target is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

name

source

nameOnDisk

Optional member that is present for executable and library targets that are linked or archived into a single primary artifact. The value is a string specifying the file name of that artifact on disk.

artifacts

Optional member that is present for executable and library targets that produce artifacts on disk meant for consumption by dependents. The value is a JSON array of entries corresponding to the artifacts. Each entry is a JSON object containing one member:

isGeneratorProvided

Optional member that is present with boolean value true if the target is provided by CMake’s build system generator rather than by a command in the source code.

install

Optional member that is present when the target has an install() rule. The value is a JSON object with members:

path

destinations

A JSON array of entries specifying an install destination path. Each entry is a JSON object with members:

backtrace

Optional member that is present when a CMake language backtrace to the install() command invocation that specified this destination is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

language

A string specifying the language (e.g. C, CXX, Fortran) of the toolchain is used to invoke the linker.

commandFragments

Optional member that is present when fragments of the link command line invocation are available. The value is a JSON array of entries specifying ordered fragments. Each entry is a JSON object with members:
fragment

A string specifying a fragment of the link command line invocation. The value is encoded in the build system’s native shell format.

•

Optional member that is present with boolean value true when link-time optimization (a.k.a. interprocedural optimization or link-time code generation) is enabled.

sysroot

Optional member that is present when the CMAKE_SYSROOT_LINK or CMAKE_SYSROOT variable is defined. The value is a JSON object with one member:

archive

Optional member that is present for static library targets. The value is a JSON object with members describing the archive step:
commandFragments

Optional member that is present when fragments of the archiver command line invocation are available. The value is a JSON array of entries specifying the fragments. Each entry is a JSON object with members:
fragment

A string specifying a fragment of the archiver command line invocation. The value is encoded in the build system’s native shell format.

•

dependencies

Optional member that is present when the target depends on other targets. The value is a JSON array of entries corresponding to the dependencies. Each entry is a JSON object with members:

backtrace

Optional member that is present when a CMake language backtrace to the add_dependencies(), target_link_libraries(), or other command invocation that created this dependency is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

sources

A JSON array of entries corresponding to the target’s source files. Each entry is a JSON object with members:

compileGroupIndex

Optional member that is present when the source is compiled. The value is an unsigned integer 0-based index into the compileGroups array.

sourceGroupIndex

Optional member that is present when the source is part of a source group either via the source_group() command or by default. The value is an unsigned integer 0-based index into the sourceGroups array.

isGenerated

Optional member that is present with boolean value true if the source is GENERATED.

backtrace

Optional member that is present when a CMake language backtrace to the target_sources(), add_executable(), add_library(), add_custom_target(), or other command invocation that added this source to the target is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

sourceGroups

Optional member that is present when sources are grouped together by the source_group() command or by default. The value is a JSON array of entries corresponding to the groups. Each entry is a JSON object with members:

sourceIndexes

A JSON array listing the sources belonging to the group. Each entry is an unsigned integer 0-based index into the main sources array for the target.

compileGroups

Optional member that is present when the target has sources that compile. The value is a JSON array of entries corresponding to groups of sources that all compile with the same settings. Each entry is a JSON object with members:
sourceIndexes

A JSON array listing the sources belonging to the group. Each entry is an unsigned integer 0-based index into the main sources array for the target.

language

A string specifying the language (e.g. C, CXX, Fortran) of the toolchain is used to compile the source file.

compileCommandFragments

Optional member that is present when fragments of the compiler command line invocation are available. The value is a JSON array of entries specifying ordered fragments. Each entry is a JSON object with one member:
fragment

A string specifying a fragment of the compile command line invocation. The value is encoded in the build system’s native shell format.

includes

Optional member that is present when there are include directories. The value is a JSON array with an entry for each directory. Each entry is a JSON object with members:

isSystem

Optional member that is present with boolean value true if the include directory is marked as a system include directory.

backtrace

Optional member that is present when a CMake language backtrace to the target_include_directories() or other command invocation that added this include directory is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

precompileHeaders

Optional member that is present when target_precompile_headers() or other command invocations set PRECOMPILE_HEADERS on the target. The value is a JSON array with an entry for each header. Each entry is a JSON object with members:

backtrace

Optional member that is present when a CMake language backtrace to the target_precompile_headers() or other command invocation that added this precompiled header is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

This field was added in codemodel version 2.1.

defines

Optional member that is present when there are preprocessor definitions. The value is a JSON array with an entry for each definition. Each entry is a JSON object with members:

backtrace

Optional member that is present when a CMake language backtrace to the target_compile_definitions() or other command invocation that added this preprocessor definition is available. The value is an unsigned integer 0-based index into the backtraceGraph member’s nodes array.

sysroot

Optional member that is present when the CMAKE_SYSROOT_COMPILE or CMAKE_SYSROOT variable is defined. The value is a JSON object with one member:

backtraceGraph

A JSON object describing the graph of backtraces whose nodes are referenced from backtrace members elsewhere. The members are:

file

command

An optional member present when the node represents a command invocation within the file. The value is an unsigned integer 0-based index into the backtrace commands array.

commands

A JSON array listing command names referenced by backtrace nodes. Each entry is a string specifying a command name.

Object Kind “cache”
The cache object kind lists cache entries. These are the CMake Language Variables stored in the persistent cache (CMakeCache.txt) for the build tree.

There is only one cache object major version, version 2. Version 1 does not exist to avoid confusion with that from cmake-server(7) mode.

“cache” version 2
cache object version 2 is a JSON object:

{
  "kind": "cache",
  "version": { "major": 2, "minor": 0 },
  "entries": [
    {
      "name": "BUILD_SHARED_LIBS",
      "value": "ON",
      "type": "BOOL",
      "properties": [
        {
          "name": "HELPSTRING",
          "value": "Build shared libraries"
        }
      ]
    },
    {
      "name": "CMAKE_GENERATOR",
      "value": "Unix Makefiles",
      "type": "INTERNAL",
      "properties": [
        {
          "name": "HELPSTRING",
          "value": "Name of generator."
        }
      ]
    }
  ]
}

The members specific to cache objects are:
entries

A JSON array whose entries are each a JSON object specifying a cache entry. The members of each entry are:

properties

A JSON array of entries specifying associated cache entry properties. Each entry is a JSON object containing members:

Object Kind “cmakeFiles”
The cmakeFiles object kind lists files used by CMake while configuring and generating the build system. These include the CMakeLists.txt files as well as included .cmake files.

There is only one cmakeFiles object major version, version 1.

“cmakeFiles” version 1
cmakeFiles object version 1 is a JSON object:

{
  "kind": "cmakeFiles",
  "version": { "major": 1, "minor": 0 },
  "paths": {
    "build": "/path/to/top-level-build-dir",
    "source": "/path/to/top-level-source-dir"
  },
  "inputs": [
    {
      "path": "CMakeLists.txt"
    },
    {
      "isGenerated": true,
      "path": "/path/to/top-level-build-dir/.../CMakeSystem.cmake"
    },
    {
      "isExternal": true,
      "path": "/path/to/external/third-party/module.cmake"
    },
    {
      "isCMake": true,
      "isExternal": true,
      "path": "/path/to/cmake/Modules/CMakeGenericSystem.cmake"
    }
  ]
}

The members specific to cmakeFiles objects are:

source

A JSON array whose entries are each a JSON object specifying an input file used by CMake when configuring and generating the build system. The members of each entry are:

isGenerated

Optional member that is present with boolean value true if the path specifies a file that is under the top-level build directory and the build is out-of-source. This member is not available on in-source builds.

isExternal

Optional member that is present with boolean value true if the path specifies a file that is not under the top-level source or build directories.

isCMake

Optional member that is present with boolean value true if the path specifies a file in the CMake installation.

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