In CMake, creating construct targets that do not produce a ultimate executable or library is achievable via the `add_custom_target()` command. This permits execution of specified instructions at totally different levels of the construct course of. For instance, a customized goal may be used to generate supply code, copy recordsdata, or run exterior instruments. A easy instance would contain making a goal that executes a script after compilation:
add_custom_target(run_my_script ALL COMMAND ${CMAKE_COMMAND} -E copy $ /some/vacation spot/)This performance supplies vital flexibility and management over advanced construct pipelines. Managing ancillary duties alongside core compilation and linking turns into streamlined. Traditionally, reaching comparable outcomes concerned advanced Makefile manipulations or counting on exterior scripting options. This technique supplies a extra built-in and moveable strategy. This functionality is very beneficial in initiatives involving code technology, pre- or post-processing steps, or the mixing of exterior instruments and sources instantly inside the construct system.
This text will discover the sensible utility of customized targets in CMake. Subjects lined embrace defining dependencies between targets, controlling execution timing, and integrating customized instructions seamlessly right into a challenge’s construct course of. Moreover, greatest practices and superior utilization eventualities, reminiscent of conditional execution and dealing with advanced dependencies, might be mentioned.
1. Construct course of integration
Construct course of integration lies on the coronary heart of `add_custom_target`’s utility. It allows seamless incorporation of duties circuitously associated to compilation or linking, but important for challenge completion, inside the CMake construct system. This eliminates the necessity for separate scripts or guide intervention, making certain constant and repeatable builds. By defining customized targets, builders specify instructions and dependencies, permitting CMake to orchestrate their execution inside the broader construct course of. This tight integration simplifies advanced workflows by automating ancillary duties, reminiscent of code technology, testing, packaging, and deployment. For example, producing code from an Interface Definition Language (IDL) file earlier than compilation might be built-in as a customized goal, guaranteeing the generated code is all the time present.
Take into account a challenge requiring information file preprocessing earlier than compilation. With out construct course of integration, this preprocessing step would want guide execution or a separate script. `add_custom_target` permits defining a goal particularly for this preprocessing, mechanically executed earlier than the compilation goal, making certain information recordsdata are all the time preprocessed. One other instance is post-build actions, reminiscent of packaging or deployment. A customized goal can automate these steps, triggered after profitable compilation, eliminating guide intervention and making certain constant outputs. This simplifies steady integration and supply pipelines by automating key steps inside the construct course of itself.
Efficient construct course of integration via `add_custom_target` enhances challenge maintainability, reduces errors related to guide steps, and promotes automation. Integrating important duties inside the construct system ensures constant execution throughout totally different growth environments and simplifies collaboration. Whereas managing dependencies between customized targets and different construct targets is essential for proper execution order, the power to outline pre- and post-build actions supplies fine-grained management over the whole construct course of. Understanding this integration is prime for leveraging the complete potential of CMake and streamlining advanced challenge workflows.
2. Non-executable Targets
A distinguishing function of `add_custom_target` is its capability to outline non-executable targets. Not like targets representing executable binaries or libraries, these targets function orchestrators of particular actions inside the construct course of. They don’t produce a ultimate compiled output however as a substitute execute designated instructions. This attribute is essential for integrating duties like code technology, file manipulation, or operating exterior instruments, none of which end in a standard compiled artifact. The significance of non-executable targets stems from their capability to encapsulate and handle ancillary operations inside the CMake framework. Take into account a state of affairs the place a challenge requires pre-processing of enter information recordsdata earlier than compilation. A non-executable goal might be outlined to carry out this preprocessing, making certain the duty is executed mechanically as a part of the construct course of with out producing a separate executable file.
Actual-life examples additional illustrate the sensible significance. In a challenge using protocol buffers, a non-executable goal may be outlined to generate supply code from .proto recordsdata. This goal would execute the protocol buffer compiler, making certain generated code stays in keeping with the definitions. Equally, initiatives requiring customized code technology instruments can make use of non-executable targets to execute these instruments in the course of the construct course of, integrating seamlessly with compilation and different construct steps. Moreover, non-executable targets can orchestrate duties past code technology. They can be utilized to repeat recordsdata, run testing scripts, generate documentation, or carry out another motion mandatory for challenge completion, all inside the outlined construct construction.
Understanding the function of non-executable targets is crucial for harnessing the complete energy of `add_custom_target`. It permits builders to encapsulate numerous operations inside the construct system, selling maintainability and automation. Challenges related to managing exterior dependencies, customized instruments, and complicated construct steps are addressed via this mechanism. The combination of non-executable targets allows a complete and streamlined construct course of, making certain all mandatory actions, from code technology to post-build deployment, are managed effectively inside the CMake surroundings.
3. Customized instructions execution
The core performance of `add_custom_target` revolves round customized command execution. This functionality allows the mixing of just about any shell command inside the CMake construct course of. Instructions are specified instantly inside the `add_custom_target` name, offering flexibility for duties starting from easy file copies to advanced script executions. This direct integration eliminates the necessity for exterior scripting or guide intervention, making certain all build-related actions are managed constantly inside CMake. The cause-and-effect relationship is evident: defining a customized goal causes the desired instructions to be executed in the course of the construct course of, based on the desired dependencies and timing.
The significance of customized instructions as a element of `add_custom_target` can’t be overstated. It is this function that enables extending CMake past compilation and linking, enabling integration of numerous duties like code technology, testing, packaging, and deployment. Take into account a real-life instance the place a challenge makes use of a customized code generator. A customized goal might be outlined to execute this generator earlier than compilation, making certain the generated code is all the time up-to-date. One other sensible state of affairs includes post-build actions: a customized command might bundle the compiled output into an archive or deploy it to a particular location. These examples illustrate the sensible significance of understanding this connection: it empowers builders to automate advanced workflows, making certain consistency and repeatability throughout totally different growth environments.
Moreover, the power to execute customized instructions introduces flexibility in managing exterior instruments. Dependencies on exterior instruments might be explicitly outlined inside CMake, making certain they’re obtainable in the course of the construct course of. Customized instructions can then invoke these instruments, integrating them seamlessly into the workflow. This simplifies toolchain administration and promotes challenge portability by capturing these dependencies inside the CMake configuration. Nonetheless, warning is important when defining customized instructions. Platform-specific instructions can restrict portability, and complicated command constructions require cautious consideration for maintainability. By understanding the nuances of customized command execution inside `add_custom_target`, builders can harness its full potential to create strong and versatile construct processes.
4. Dependency Administration
Dependency administration is a important side of leveraging `add_custom_target` successfully. This includes specifying relationships between customized targets and different targets inside the CMake challenge. Establishing clear dependencies ensures appropriate execution order. A customized goal may rely upon the technology of particular recordsdata or the completion of different construct steps. CMake makes use of these dependencies to find out the order during which targets are constructed, guaranteeing that stipulations are glad earlier than a goal is executed. This cause-and-effect relationship is prime: defining a dependency causes CMake to execute the dependent goal solely after the dependency is met.
The significance of dependency administration as a element of `add_custom_target` lies in its capability to orchestrate advanced construct processes. Take into account a challenge involving code technology adopted by compilation. The compilation goal should rely upon the customized goal chargeable for code technology. This dependency ensures the generated code exists earlier than compilation begins, stopping construct errors and making certain appropriate outputs. A sensible instance includes producing documentation. A documentation technology goal may rely upon the profitable compilation of the challenge’s supply code. This dependency ensures that documentation is generated solely after a profitable construct, reflecting the present state of the codebase. One other state of affairs includes pre-processing information recordsdata: a customized goal performing preprocessing may very well be a dependency for the principle compilation goal, making certain information is processed earlier than compilation commences.
Sensible significance arises from the power to outline dependencies between customized targets and different construct targets, enabling advanced workflows and making certain appropriate execution sequences. Challenges related to construct order and timing are mitigated via dependency administration. Incorrect dependencies can result in construct failures or inconsistent outputs, highlighting the significance of fastidiously contemplating and defining these relationships. Understanding the function of dependency administration inside `add_custom_target` permits builders to create strong and dependable construct processes that automate advanced duties, making certain appropriate execution order and selling challenge maintainability.
5. Pre-build actions
Pre-build actions, facilitated by `add_custom_target`, characterize a vital mechanism for executing duties earlier than the first construct steps start. Defining a goal with the `PRE_BUILD` possibility ensures specified instructions run earlier than the compilation or linking of dependent targets. This cause-and-effect relationship is crucial: specifying `PRE_BUILD` causes designated instructions to execute earlier than subsequent construct levels. This functionality is prime for duties that generate supply code, put together information recordsdata, or configure the construct surroundings previous to compilation. Pre-build actions function integral parts of `add_custom_target`, extending CMake’s capabilities past conventional construct operations.
Actual-life examples illustrate the sensible worth of pre-build actions. Take into account a challenge utilizing a code generator. A customized goal with the `PRE_BUILD` possibility can execute the code generator earlier than compilation, guaranteeing the generated code is all the time present. One other state of affairs includes information file preprocessing. A pre-build motion might carry out transformations or validations on enter information, making certain the compiler receives appropriately formatted information. Moreover, configuring the construct surroundings, reminiscent of setting surroundings variables or producing configuration recordsdata, might be effectively dealt with via pre-build actions. These examples exhibit how pre-build actions facilitate advanced construct workflows by making certain mandatory stipulations are met earlier than core construct steps start.
The sensible significance of understanding pre-build actions inside the context of `add_custom_target` lies within the capability to streamline and automate advanced construct procedures. Duties that beforehand required guide intervention or separate scripting might be seamlessly built-in into the CMake construct course of. This integration improves construct reliability, reduces guide errors, and simplifies the administration of advanced initiatives. Nonetheless, cautious consideration of dependencies and execution order stays essential. Incorrectly configured pre-build actions can result in construct failures or surprising habits. Correctly carried out pre-build actions, nevertheless, are instrumental in creating strong, automated, and maintainable construct programs.
6. Submit-build actions
Submit-build actions, enabled via `add_custom_target`, present a mechanism for executing instructions after a goal has been efficiently constructed. This functionality is crucial for automating duties that rely upon the finished construct output, reminiscent of putting in recordsdata, producing documentation, or operating exams. Defining a goal with the `POST_BUILD` possibility ensures specified instructions execute solely after the profitable completion of the goal’s major construct course of. This cause-and-effect relationship is essential: the `POST_BUILD` specification causes the related instructions to run after the goal construct completes. Understanding post-build actions is crucial for leveraging the complete potential of `add_custom_target` and automating advanced construct workflows.
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Set up
A typical use case for post-build actions is putting in constructed artifacts to designated places. This could contain copying executables, libraries, or information recordsdata to particular directories. For instance, a post-build motion might copy a newly compiled executable to a system listing, making it readily accessible. Automating set up simplifies deployment and ensures constant outcomes throughout totally different environments.
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Packaging
Creating distributable packages is one other frequent utility of post-build actions. A customized goal might be outlined to bundle compiled outputs, documentation, and different mandatory recordsdata into an archive format, reminiscent of a zipper or tarball. This automates the creation of distributable packages, streamlining launch processes and making certain constant bundle contents.
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Testing
Submit-build actions can set off automated exams after a profitable construct. A customized goal might execute check scripts or invoke testing frameworks, offering quick suggestions on code modifications. This integration of testing inside the construct course of facilitates steady integration and ensures constant check execution.
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Documentation Era
Producing documentation after a profitable construct is one other beneficial utility. Submit-build actions can execute documentation mills, reminiscent of Doxygen, to create up-to-date documentation reflecting the present state of the codebase. This automation ensures documentation stays synchronized with the code and simplifies the documentation course of.
These examples spotlight the flexibility of post-build actions inside the `add_custom_target` framework. They illustrate how duties depending on profitable construct completion might be seamlessly built-in into the construct course of, selling automation, consistency, and effectivity. By understanding and using post-build actions successfully, builders can create strong and streamlined construct programs that deal with advanced workflows with ease, enhancing total challenge maintainability and decreasing the danger of guide errors.
7. File technology duties
`add_custom_target` in CMake performs a pivotal function in automating file technology duties, which are sometimes important steps in advanced construct processes. These duties may contain producing supply code from templates, configuration recordsdata from consumer enter, or information recordsdata via preprocessing. Integrating file technology seamlessly inside the construct system ensures these recordsdata are all the time up-to-date and constantly produced, eliminating guide intervention and decreasing potential errors.
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Supply Code Era
Producing supply code from higher-level definitions or templates is a standard use case. Take into account a challenge utilizing protocol buffers or different Interface Definition Languages (IDLs). Customized targets can execute instruments that course of these definitions, producing the mandatory supply code recordsdata earlier than compilation. This ensures code consistency and simplifies the administration of evolving interfaces. For instance, a goal might automate the execution of a protocol buffer compiler to generate C++ code from
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Configuration File Era
Construct processes usually require configuration recordsdata tailor-made to particular construct environments or consumer preferences. Customized targets can automate the technology of those recordsdata primarily based on enter parameters, templates, or different information sources. This dynamic technology ensures configuration recordsdata mirror the present construct settings and eliminates the necessity for guide updates. A sensible instance might contain producing platform-specific configuration recordsdata primarily based on CMake variables.
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Preprocessing Information Recordsdata
Remodeling or validating information recordsdata earlier than compilation or different processing steps is one other essential utility. Customized targets can execute scripts or instruments that preprocess enter information, making certain it meets particular formatting or validation necessities. This preprocessing step ensures information integrity and simplifies subsequent construct levels. An actual-world state of affairs might contain changing information recordsdata from one format to a different or validating information in opposition to a schema earlier than it is utilized by the principle utility.
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Construct Artifact Administration
Past producing supply code or configuration recordsdata, customized targets also can handle different build-related artifacts. This may contain producing model data recordsdata, timestamps, or construct manifests. Automating these duties ensures consistency and simplifies monitoring construct outputs. For example, a customized goal might generate a file containing the present construct date and time, embedding this data inside the ultimate utility.
These numerous functions spotlight the significance of file technology duties inside the context of `add_custom_target`. By automating these duties inside the construct system, CMake ensures constant and repeatable builds, simplifying advanced workflows and decreasing the danger of errors related to guide processes. The combination of file technology capabilities inside CMake empowers builders to handle advanced initiatives effectively and reliably, selling maintainability and code high quality.
8. Code technology steps
Code technology performs a important function in lots of software program initiatives, automating the creation of supply code from templates, domain-specific languages (DSLs), or different enter codecs. `add_custom_target` in CMake supplies a robust mechanism for integrating these code technology steps instantly into the construct course of. This integration ensures generated code is all the time up-to-date and in keeping with the challenge’s construct configuration, eliminating guide code technology processes and decreasing potential errors. Defining a customized goal for code technology establishes a transparent cause-and-effect relationship: invoking the goal causes the desired code technology instruments or scripts to execute, producing the required supply recordsdata. The significance of this integration as a element of `add_custom_target` lies in its capability to automate a important, usually advanced, a part of the construct workflow.
Actual-world examples illustrate the sensible significance. Take into account a challenge utilizing protocol buffers. A customized goal might be outlined to execute the protocol buffer compiler, producing C++ or different language bindings from .proto recordsdata. This ensures generated code stays synchronized with the interface definitions. One other widespread state of affairs includes consumer interface frameworks that generate code from UI descriptions. A customized goal can automate this course of, conserving the generated code aligned with the UI design. Additional functions embrace producing information entry code from database schemas or creating platform-specific code from a standard template. These examples exhibit how `add_custom_target` streamlines code technology, decreasing guide effort and making certain code consistency.
The sensible significance of understanding this connection is substantial. Automating code technology inside the CMake construct course of improves construct reliability, reduces guide errors, and simplifies the administration of advanced initiatives. It additionally facilitates constant code technology throughout totally different growth environments. Nonetheless, potential challenges exist. Managing dependencies between generated code and different supply recordsdata requires cautious consideration. Round dependencies or incorrect construct order can result in construct failures. Efficiently integrating code technology steps inside CMake empowers builders to automate essential duties, improve construct consistency, and streamline growth workflows. This integration in the end contributes to improved challenge maintainability and lowered growth time by automating a key side of the software program growth lifecycle.
9. Exterior instrument invocation
The power to invoke exterior instruments kinds a cornerstone of `add_custom_target`’s versatility inside CMake. This performance permits integrating pre-existing instruments or utilities seamlessly into the construct course of, extending CMake’s capabilities past compilation and linking. Defining a customized goal to invoke an exterior instrument establishes a transparent cause-and-effect relationship: executing the goal causes the desired instrument to be invoked with designated parameters. The significance of exterior instrument invocation as a element of `add_custom_target` lies in its capability to leverage current instruments inside a unified construct surroundings, automating advanced workflows and decreasing guide intervention.
Sensible functions are quite a few. Take into account a challenge requiring code technology from a specialised instrument. A customized goal might be outlined to invoke this instrument, producing the mandatory supply code earlier than compilation. Equally, initiatives using exterior testing frameworks can make use of customized targets to automate check execution as a part of the construct course of. Different examples embrace invoking static evaluation instruments, pre-processing information recordsdata with devoted utilities, or producing documentation with exterior documentation mills. These real-life eventualities exhibit how exterior instrument invocation empowers builders to combine a various array of instruments seamlessly inside the CMake construct system, simplifying advanced workflows and selling automation.
Moreover, the sensible significance of understanding this connection extends past easy instrument execution. Managing dependencies on exterior instruments turns into essential. CMake supplies mechanisms for finding and verifying the presence of required instruments, making certain they’re obtainable in the course of the construct course of. This facilitates challenge portability by explicitly defining instrument dependencies inside the CMake configuration. Nonetheless, platform-specific instrument dependencies can current challenges. Abstraction layers or conditional logic may be required to deal with platform variations and guarantee construct consistency throughout totally different environments. Efficiently integrating exterior instrument invocation inside CMake enhances construct flexibility, enabling environment friendly automation and integration of numerous instruments. This functionality unlocks alternatives for streamlining advanced construct pipelines, decreasing guide effort, and selling constant, dependable builds throughout varied platforms.
Steadily Requested Questions on Customized Targets in CMake
This part addresses widespread questions and potential factors of confusion relating to the usage of add_custom_target inside CMake initiatives. A transparent understanding of those continuously requested questions will support in successfully leveraging this highly effective function.
Query 1: How does a customized goal differ from an everyday construct goal?
Customized targets don’t produce construct artifacts like executables or libraries. They execute specified instructions, enabling integration of duties like code technology, testing, or file manipulation inside the construct course of.
Query 2: How is the execution order of customized targets decided?
Execution order is ruled by dependencies. Specifying dependencies between targets ensures stipulations are met earlier than a goal executes. The ALL key phrase can be utilized to schedule execution for each construct.
Query 3: Can customized targets have dependencies on recordsdata?
Sure, dependencies on recordsdata are attainable. This ensures the goal executes provided that the desired recordsdata exist or have been modified because the final construct. That is essential for duties like code technology depending on enter recordsdata.
Query 4: How are customized targets used for pre- and post-build actions?
The PRE_BUILD and POST_BUILD arguments specify when a customized goal’s instructions ought to execute relative to the dependent goal. PRE_BUILD instructions execute earlier than, and POST_BUILD instructions execute after the dependent goal’s construct course of.
Query 5: What are the portability implications of utilizing platform-specific instructions in customized targets?
Platform-specific instructions can restrict cross-platform compatibility. Utilizing CMake’s built-in instructions or offering platform-specific implementations via generator expressions enhances portability.
Query 6: How can advanced command sequences be managed inside customized targets?
Complicated sequences might be managed by encapsulating them inside scripts invoked by the customized goal. This improves maintainability and readability of the CMakeLists.txt file.
Understanding these widespread questions and issues helps builders make the most of add_custom_target successfully, making certain strong and maintainable CMake initiatives.
The next part delves into superior utilization eventualities and sensible examples, additional illustrating the capabilities and suppleness of customized targets in CMake.
Suggestions for Efficient Use of Customized Targets
This part affords sensible steering on leveraging customized targets successfully inside CMake initiatives. The following tips handle widespread eventualities and greatest practices to make sure strong and maintainable construct processes.
Tip 1: Clearly Outline Dependencies
Explicitly specify dependencies between customized targets and different targets or recordsdata. This ensures appropriate execution order and prevents surprising construct habits. Make the most of DEPENDS argument inside add_custom_target to ascertain dependencies on recordsdata or different targets.
add_custom_target(generate_code DEPENDS enter.txt)Tip 2: Make the most of Generator Expressions for Portability
Make use of generator expressions for platform-specific logic inside customized instructions. This enhances cross-platform compatibility and avoids hardcoding platform-specific paths or instructions. Generator expressions permit conditional logic primarily based on the goal platform or different construct configurations.
add_custom_command(TARGET my_target POST_BUILD COMMAND ${CMAKE_COMMAND} -E copy $ $/bin) Tip 3: Encapsulate Complicated Instructions in Scripts
For intricate command sequences, create devoted scripts and invoke them via customized targets. This improves readability and maintainability of CMakeLists.txt recordsdata. Scripts can include advanced logic or platform-specific instructions, simplifying administration inside CMake.
add_custom_target(run_script COMMAND ./my_script.sh)
Tip 4: Leverage the ALL Key phrase Judiciously
Use the ALL key phrase with warning. Including a customized goal to ALL ensures its execution with each construct, which may be pointless for sure duties. Take into account dependencies fastidiously earlier than including customized targets to ALL to keep away from pointless construct overhead.
add_custom_target(my_target ALL COMMAND my_command)
Tip 5: Make use of COMMENT for Readability
Doc customized targets with descriptive feedback. This clarifies their objective and aids in understanding the construct course of. Feedback present context and facilitate upkeep of advanced construct configurations.
add_custom_target(generate_docs ALL COMMENT "Producing documentation")
Tip 6: Take into account BYPRODUCTS for Generated Recordsdata
When a customized goal generates recordsdata, declare them as BYPRODUCTS. This informs CMake concerning the generated recordsdata, enhancing dependency monitoring and construct effectivity.
add_custom_command(OUTPUT generated.h COMMAND generate_header.sh BYPRODUCTS generated.h)
Tip 7: Make the most of WORKING_DIRECTORY for Particular Paths
Use the WORKING_DIRECTORY argument to specify the listing the place customized instructions ought to execute. That is essential when instructions depend on relative paths or particular surroundings settings.
add_custom_command(TARGET my_target POST_BUILD COMMAND my_script.sh WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/scripts) By adhering to those ideas, builders can harness the complete potential of customized targets, creating well-structured, maintainable, and environment friendly construct processes inside CMake.
The following tips spotlight key concerns for efficient customized goal implementation, paving the way in which for a sturdy and streamlined construct course of. The next conclusion summarizes the important thing benefits and potential of customized targets inside CMake initiatives.
Conclusion
This exploration of CMake’s add_custom_target performance has illuminated its significance in managing advanced construct processes. From automating code technology and exterior instrument invocation to orchestrating pre- and post-build actions, customized targets provide a robust mechanism for extending CMake’s capabilities past conventional compilation and linking. Dependency administration, coupled with choices like PRE_BUILD, POST_BUILD, and BYPRODUCTS, supplies fine-grained management over construct execution, making certain seamless integration of numerous duties inside a unified construct system. Understanding the nuances of customized targets, together with their non-executable nature and their function in managing dependencies, is essential for harnessing their full potential.
Efficient utilization of add_custom_target empowers builders to create strong, automated, and maintainable construct processes. By embracing the flexibleness provided by customized targets, initiatives can streamline workflows, scale back guide intervention, and guarantee construct consistency throughout numerous platforms. As initiatives develop in complexity, the strategic utility of this performance turns into more and more important for managing the intricacies of recent software program growth, paving the way in which for environment friendly, dependable, and scalable construct programs.
