This chapter provides more in-depth information, and describes how such
projects can be created and maintained.
6.1. Description of the Projects
6.1.2. Contents of project files
Project files contain all the information that describe the organization of
your source files, object files and executables.
A project file can contain comments, which have the same format as in Ada, that
is they start by “–” and extend to the end of the line. You can add comments
when you edit the project file manually. GPS will attempt to preserve them when
you save the project through the menu, but this will not always be possible. It
helps if the comments are put at the end of the line, as in:
project Default is
for Source_Dirs use (); -- No source in this project
end Default;
Generally, one project file will not be enough to describe a complex
organization. In this case, you will create and use a project hierarchy, with a
root project importing other sub projects. Each of the projects and sub
projects is responsible for its own set of sources (compiling them with the
appropriate switches, put the resulting files in the right directories, ...).
Each project contains the following information (see the GNAT user’s guide for
the full list)
List of imported projects:
.. index:: project; imported project
When you are compiling sources from this project, the builder will first make
sure that all the imported projects have been correctly recompiled and are
up-to-date. This way, dependencies between source files are properly handled.
If one of the source files of project A depends on some source files from
project B, then B must be imported by A. If this isn’t the case, the compiler
will complain that some of the source files cannot be found.
One important rule is that each source file name must be unique in the
project hierarchy (i.e. a file cannot be under control of two different
projects). This ensures that the same file will be found no matter what
project is managing the source file that uses
List of source directories:
.. index:: project; source directory
All the sources managed by a project are found in one or more source
directories. Each project can have multiple source directories, and a given
source directory might be shared by multiple projects.
Object directory:
.. index:: project; object directory
When the sources of the project are compiled, the resulting object files are
put into this object directory. There exist exactly one object directory for
each project. If you need to split the object files among multiple object
directories, you need to create multiple projects importing one another as
appropriate.
When sources from imported sub-projects are recompiled, the resulting object
files are put in the sub project’s own object directory, and will never
pollute the parent’s object directory.
Exec directory:
.. index:: project; exec directory
When a set of object files is linked into an executable, this executable is
put in the exec directory of the project file. If this attribute is
unspecified, the object directory is used.
List of source files:
.. index:: project; source files
The project is responsible for managing a set of source files. These files
can be written in any programming languages. Currently, the graphical
interface supports Ada, C and C++.
The default to find this set of source files is to take all the files in the
source directories that follow the naming scheme (see below) for each
language. In addition if you edit the project file manually, it is possible
to provide an explicit list of source files.
This attribute cannot be modified graphically yet.
List of main units:
.. index:: project; main units
The main units of a project (or main files in some languages) are the units
that contain the main subprogram of the application, and that can be used to
link the rest of the application.
The name of the file is generally related to the name of the executable.
A given project file hierarchy can be used to compile and link several
executables. GPS will automatically update the Compile, Run and Debug menu
with the list of executables, based on this list.
Naming schemes:
.. index:: project; naming schemes
The naming scheme refers to the way files are named for each languages of the
project. This is used by GPS to choose the language support to use when a
source file is opened. This is also used to know what tools should be used to
compile or otherwise work with a source file.
Embedded targets and cross environments:
.. index:: project; cross environment
GPS supports cross environment software development: GPS itself can run on a
given host, such as GNU/Linux, while compilations, runs and debugging occur
on a different remote host, such as Sun/Solaris.
GPS also supports embedded targets (VxWorks, ...) by specifying alternate
names for the build and debug tools.
The project file contains the information required to log on the remote host.
Tools:
Project files provide a simple way to specify the compiler and debugger
commands to use.
Switches:
.. index:: project; switches
Each tool that is used by GPS (compiler, pretty-printer, debugger, ...) has
its own set of switches. Moreover, these switches may depend on the specific
file being processed, and the programming language it is written in.
6.2. Supported Languages
Another information stored in the project is the list of languages that this
project knows about. GPS support any number of language, with any name you
choose. However, advanced support is only provided by default for some
languages (Ada, C and C++), and you can specify other properties of the
languages through customization files
(Adding support for new languages).
By default, the graphical interface will only give you a choice of languages
among the ones that are known to GPS at that point, either through the default
GPS support or your customization files. But you can also edit the project
files by hand to add support for any language.
Languages are a very important part of the project definition. For each
language, you should specify a naming scheme that allows GPS to associate files
with that language. You would for instance specify that all .adb files
are Ada, all .txt files are standard text files, and so on.
Only the files that have a known language associated with them are displayed in
the Project View, or available for easy selection through the
menu. Similarly, only these files
are shown in the Version Control System interface.
It is therefore important to properly setup your project to make these files
available conveniently in GPS, although of course you can still open any file
through the menu.
If your project includes some README files, or other text files, you should add
“txt” as a language (or any other name you want), and make sure that these
files are associated with that language in the .
By default, GPS provides support for a number of languages. In most cases, this
support takes the form of syntax highlighting in the editor, and possibly the
Outline View. Other languages have advanced cross-references available.
All the supported languages can be added to the project, but you can also add
your own languages as you need (either by editing the project files by hand, or
by creating XML files to add GPS support for these languages, which will then
show in the project properties editor graphically).
6.3. Scenarios and Configuration Variables
The behavior of projects can be further tailored by the use of scenarios.
All the attributes of a project, except its list of imported projects, can be
chosen based on the value of external variables, whose value is generally
coming from the host computer environment, or directly set in GPS. The
interface to manipulate these scenarios is the scenario view, which can be
displayed by selecting the menu
(The Scenario View) It can be convenient to drag this
window with your mouse, and drop it above the project view, so that you can see
both at the same time.
This area allows you to select new values for the scenario variables defined in
your project, and thus change dynamically the view GPS has of your project and
your source files.
This facility can for instance be used to compile all the sources either in
debug mode (so that the executables can be run in the debugger), or in
optimized mode (to reduce the space and increase the speed when delivering the
software). In this configuration scenario, all the attributes (source
directories, tools, ...) remain the same, except for the compilation switches.
It would be more difficult to maintain a completely separate hierarchy of
project, and it is much more efficient to create a new configuration variable
and edit the switches for the appropriate scenario
(The Project Properties Editor).
There is one limitation in what GPS can do with scenario variables: although
gnatmake and gprbuild have no problem dealing with scenario variables whose
default value is not a static string (for instance a concatenation, or the
value of another scenario variable), GPS will not be able to edit such a
project graphically. Such projects will load fine in GPS though.
6.3.1. Creating new scenario variables
Creating a new scenario variable is done through the contextual menu
(right-click) in the Project View or the Scenario View itself. Select the menu
. This opens the
following dialog:
There are two main areas in this dialog: in the top line, you specify the name
of the variable. This name is used for two purposes:
It is displayed in the Scenario view
This is the name of the environment variable from which the initial value is
read. When GPS is started, all configuration variables are initialized from
the host computer environment, although you can of course change its value
later on inside GPS. Note that selecting a new value for the scenario
variable does not change the actual value of the environment variable, which
is only used to get the default initial value of the scenario variable.
When you spawn external tools like gnatmake for instance, you can also
specify the value they will use for the scenario variable by using a command
line switch, typically -X.
If you click on the arrow on the right of this name area, GPS will display the
list of all the environment variables that are currently defined. However, you
don’t need to pick the name of an existing variable, neither must the variable
exist when GPS is started.
The second part of this dialog is the list of authorized value for this
variable. Any other value will generate an error reported by GPS, and the
project won’t be loaded as a result.
One of these values is the default value (the one whose button in the Default
column is selected). This means that if the environment variable doesn’t exist
when GPS is started, GPS will behave as if it did exist with this default
value.
The list of possible values can be edited by right-clicking on the name of the
variable, and selecting one of Edit properties or Delete
variable.
6.3.2. Editing existing scenario variables
If at least one configuration variable is defined in your project, the
Scenario view will contain something similar to:
You can easily change the current value of any of these variables by clicking
on the value. This will display a pop-up window with the list of possible
values, from which you select the one you wish to use.
As soon as a new value is selected, GPS will recompute the project view (in
case source directories, object directories or list of source files have
changed). A number of things will also be updated (like the list of executables
in the Compile, Run and Debug menus).
Currently, GPS will not recompute the contents of the various browsers (call
graph, dependencies, ...) for this updated project. This would be too expensive
to do every time the value changes, and therefore you need to explicitly
request an update.
You can change the list of possible values for a configuration variable at any
time by clicking on the edit button in the local toolbar. This will
pop up the same dialog that is used to create new variables. This dialog also
allows you to change the name of the scenario variable. This name is the same
as the environment variable that is used to set the initial value of the
scenario variable.
Removing a variable is done by clicking the remove the button in
the local toolbar, after selecting the variable. GPS will then display a
confirmation dialog.
If you confirm that you want to delete the variable, GPS will simply remove the
variable, and from now on act as if the variable always had the value it had
when it was deleted.
6.4. Extending Projects
6.4.1. Description of extending projects
The project files were designed to support big projects, with several hundreds
or thousands of source files. In such contexts, one developer will generally
work on a subset of the sources. It is also not rare for such a project to take
several hours to fully compile. Most developers therefore do not need to have
the full copy of the project compiled on their own machine or personal disk
space.
However, it is still useful to be able to access other source files of the
application, for instance to find out whether a subprogram can be changed and
where it is currently called.
Such a setup can be achieved through extending projects. These are special
types of projects that inherit most of their attributes and source files from
another project, and can have, in their source directories, some source files
that hide/replace those inherited from the original project.
When compiling such projects, the compiler will put the newly created project
files in the extending project’s directory, and will leave the original
untouched. As a result, the original project can be shared read-only among
several developers (for instance, it is usual for this original project to be
the result of a nightly build of the application).
6.4.2. Creating extending projects
This project wizard allows you to easily create extending projects. You should
select an empty directory (which will be created automatically if needed), as
well as a list of source files you want to work on initially. New files can
also be added later.
As a result, GPS will copy the selected source files to the new directory (if
you so decided), and create a number of project files there. It will then load
a new project, which has the same properties as the previous one, except that
some files are found transparently in the new directory, and object files
resulting from the compilation are create into that directory as opposed to the
object directory of the original project.
6.4.3. Adding files to extending projects
Once you have loaded an extending project in GPS, things work mostly
transparently. If you open a file through the dialog, the files found in the local directory of your extending
project will be picked up first.
The build actions will create object files in the extending project’s
directory, leaving the original project untouched.
It might happen that you want to start working on a source file that you had
not added in the extending project when it was created. You can of course edit
the file found in the original project, provided you have write access to it.
However, it is generally better to edit it in the context of the extending
project, so that the original project can be shared among developers.
This can be done by clicking on the file in the Project view, then
selecting the menu . This will popup a
dialog asking whether you want GPS to copy the file to the extending project’s
directory for you. GPS might also create some new project files in that
directory if necessary, and automatically reload the project as needed. From
then on, if you use the menu , GPS
will first see the file from the extending project.
Note that open editors will still be editing the same file they were before, so
you should open the new file if needed.
6.5. Disabling Project Edition Features
The project files should generally be considered as part of the sources, and
thus be put under control of a version control system. As such, you might want
to prevent accidental editing of the project files, either by you or some other
person using the same GPS installation.
The main thing to do to prevent such accidental edition is to change the write
permissions on the project files themselves. On Unix systems, you could also
change the owner of the file. When GPS cannot write a project file, it will
report an error to the user.
However, the above doesn’t prevent a user from trying to do some modifications
at the GUI level, since the error message only occurs when trying to save the
project (this is by design, so that temporary modification can be done in
memory).
You can disable all the project editing related menus in GPS by adding special
startup switches. The recommended way is to create a small batch script that
spawns GPS with these switches. You should use the following command line:
gps --traceoff=MODULE.PROJECT_VIEWER --traceoff=MODULE.PROJECT_PROPERTIES
What these do it prevent the loading of the two GPS modules that are
responsible for project edition. However, this also has an impact on the python
functions that are exported by GPS, and thus could break some plug-ins. Another
solution which might apply is simply to hide the corresponding project-editing
menus and contextual menus. This could be done by creating a small python
plugin for GPS (Customizing through XML and Python files, which contains
the following code:
import GPS
GPS.Menu.get('/Project/Edit Project Properties').hide()
GPS.Contextual('Edit project properties').hide()
GPS.Contextual('Save project').hide()
GPS.Contextual('Add configuration variable').hide()
6.7. The Project Wizard
The project wizard allows you to create in a few steps a new project file. It
has a number of pages, each dedicated to editing a specific set of attributes
for the project.
The typical way to access this wizard is through the menu.
The project wizard is also launched when a new dependency is created between
two projects, through the contextual menu in the project view.
The wizard gives access to the following list of pages:
- Project type
- Project Naming
- Languages Selection
- Version Control System Selection
- Source Directories Selection
- Build Directory
- Main Units
- Library
- Naming Scheme
- Switches
6.7.1. Project Type
Several types of project wizards are provided in GPS. Depending on the
information you have or your current setup, you will choose one or the other.
Single Project
This is likely the wizard you will use most often. It creates a project file
from scratch, and asks you for the location of source directories, the object
directory, ...; The rest of this chapter describes this wizard in more
details
Project Tree
This wizard will attempt to create a set of one or more project files to
represent your current build environment. It will analyze what your sources
are, where the corresponding object files are, and will try and find some
possible setup for the project files (remember that a given .gpr
project file can be associated with a single object directory.
This wizard might not work in all cases, but is worth a try to get you
started if you already have an existing set of sources
Convert GLIDE Project (.adp)
This wizard will help you convert a .adp project file that is used by
the GLIDE environment. The same restrictions apply as above, except that the
list of source directories, object directories and tool switches are read
directly from that file.
Library Project
.. index:: project; library
This specialized wizard is similar to the Single Project wizard, except it
adds one extra page, the Library page. The output of the compilation of this
project is a library (shared or static), as opposed to an executable in the
case of Single Project.
Extending Project
.. index:: project; extending
This specialized wizard allows you to easily create extending projects
(Extending Projects).
6.7.2. Project Naming
This is the first page displayed by any of the wizard.
You must enter the name and location of the project to create. This name must
be a valid Ada identifier (i.e. start with a letter, optionally followed by a
series of digits, letters or underscores). Spaces are not allowed. Likewise,
reserved Ada keywords must be avoided. If the name is invalid, GPS will display
an error message when you press the Forward button.
Child projects can be created from this dialog. These are project whose name is
of the form Parent.Child. GPS will automatically generate the dependency to
the parent project so as to make the child project valid.
In this page, you should also select what languages the source files in this
project are written in. Currently supported languages are Ada, C and C++.
Multiple languages can be used for a single project.
The last part of this page is used to indicate how the path should be stored in
the generated project file. Most of the time, this setting will have no impact
on your work. However, if you wish to edit the project files by hand, or be
able to duplicate a project hierarchy to another location on your disk, it
might be useful to indicate that paths should be stored as relative paths (they
will be relative to the location of the project file).
6.7.3. Languages Selection
This page is used to select the programming languages used for the sources of
this project. By default, only Ada is selected. New languages can be added
to this list by using XML files, see the section on customizing GPS
(Adding support for new languages).
Additionally, this page allows you to select the toolchain used when working on
your project. There you can select one of the pre-defined toolchains or scan
your system for installed toolchains. You can also manually define some of the
tools in the toolchain such as the debugger to use, the gnat driver to use or
the gnatls tool to use.
If you need to select a toolchain for a cross environment, you should have a
look at Working in a Cross Environment for more info on this subject.
6.7.4. VCS Selection
The second page in the project wizard allows you to select which Version
Control system is to be used for the source files of this project.
GPS doesn’t attempt to automatically guess what it should use, so you must
specify it if you want the VCS operations to be available to you.
The two actions Log checker and File checker are the
name and location of programs to be run just prior an actual commit of the
files in the Version Control System. These should be used for instance if you
wish to enforce style checks before a file is actually made available to other
developers in your team.
If left blank, no program will be run.
6.7.5. Source Directories Selection
This page lists and edits the list of source directories for the project. Any
number of source directory can be used (the default is to use the directory
which contains the project file, as specified in the first page of the wizard).
If you do not specify any source directory, no source file will be associated
with the project, since GPS wouldn’t know where to look for them.
To add source directories to the project, select a directory in the top frame,
and click on the down arrow. This will add the directory to the bottom frame,
which contains the current list of source directories.
You can also add a directory and all its subdirectories recursively by using
the contextual menu in the top frame. This contextual menu also provides an
entry to create new directories, if needed.
To remove source directories from the project, select the directory in the
bottom frame, and click on the up arrow, or use the contextual menu.
All the files in these directories that match one of the language supported by
the project are automatically associated with that project.
The relative sizes of the top and bottom frame can be changed by clicking on
the separation line between the two frames and dragging the line up or down.
6.7.6. Build Directory
The object directory is the location where the files resulting from the
compilation of sources (e.g. .o files) are placed. One object
directory is associated for each project.
The exec directory is the location where the executables are put. By default,
this is the same directory as the object directory.
6.7.7. Main Units
The main units of a project are the files that should be compiled and linked to
obtain executables.
Typically, for C applications, these are the files that contain the main()
function. For Ada applications, these are the files that contain the main
subprogram each partition in the project.
These files are treated specially by GPS. Some sub-menus of
and will have predefined entries
for the main units, which makes it more convenient to compile and link your
executables.
To add main units click on the Add button. This opens a file
selection dialog. No check is currently done that the selected file belongs to
the project, but GPS will complain later if it doesn’t.
When compiled, each main unit will generate an executable, whose name is
visible in the second column in this page. If you are using a recent enough
version of GNAT (3.16 or more recent), you can change the name of this
executable by clicking in the second column and changing the name
interactively.
6.7.8. Library
This page allows you to configure your project so that the output of its
compilation is a library (shared or static), as opposed to an executable or a
simple set of objet files. This library can then be linked with other
executables (and will be automatically if the project is imported by another
one.
You need to define the attributes in the top box to transform your project into
a library project. See the tooltips that appear when you leave your mouse on
top of the label to the left of each field.
If you define any of the attributes in the Standalone Library box, you will
compile a standalone library. This is a library that takes care of its
elaboration by itself, instead of relying on its caller to elaborate it as is
standard in Ada. You also have more control over what files make up the public
interface to the library, and what files are private to the library and
invisible from the outside.
6.7.9. GNATname
This page allows you to add Ada units stored in files with irregular or
arbitrary naming conventions into you project.
To take advantage of this ability you need to specify file name patterns.
GPS will use these patterns to search for Ada units in each of source
directories specified in Source Directories Selection page.
Then GPS utilises gnatname tool to generate the required pragmas for a set
of files. Files with arbitrary naming convention are not compatible with
naming scheme customization, so next page will be skipped.
6.7.10. Naming Scheme
A naming scheme indicates the file naming conventions used in the different
languages supported by a given project. For example, all .adb files
are Ada files, all .c files are C files.
GPS is very flexible in this respect, and allows you to specify the default
extension for the files in a given programming language. GPS makes a
distinction between spec (or header) files, which generally contain no
executable code, only declarations, and body files which contain the actual
code. For languages other than Ada, this header file is used rather than the
body file when you select in the contextual
menu of editors.
In a language like Ada, the distinction between spec and body is part of the
definition of the language itself, and you should be sure to specify the
appropriate extensions.
The default naming scheme for Ada is GNAT’s naming scheme (.ads for
specs and .adb for bodies). In addition, a number of predefined naming
schemes for other compilers are available in the first combo box on the page.
You can also create your own customized scheme by entering a free text in the
text entries.
For all languages, GPS accepts exceptions to this standard naming scheme. For
instance, this let you specify that in addition to using .adb for Ada
body files, the file foo.ada should also be considered as an Ada file.
The list of exceptions is displayed in the bottom list of the naming scheme
editor. To remove entries from this list, select the line you want to remove,
and then press the Del key. The contents of the lines can be edited
interactively, by double-clicking on the line and column you want to edit.
To add new entries to this list, use the fields at the bottom of the window,
and press the update button.
GNAT and GPS both support Ada source files that contain multiple Ada units
(typically a single file would contain both the spec and the body of the unit
for instance). This is not a recommend approach if you can avoid it, since that
might trigger unnecessary recompilation of your source files. Such source files
are always handled as naming scheme exceptions, and you can specify those in
the editor by adding at 1, at 2,... after the file name for either the
spec, the body or both. The digit after at is the index (starting at 1) of
the unit in the source file.
For instance, specifying file.ada at 1 for the spec and file.ada at 2 for
the body of the unit “unit” indicates that the two components of the unit are
in the same file, first the spec, followed by the body.
6.7.11. Switches
The last page of the project wizard is used to select the default switches to
be used by the various tools that GPS calls (compiler, linker, binder, pretty
printer, ...).
This page appears as a notebook, where each page is associated with a specific
tool. All these pages have the same structure:
- Graphical selection of switches
- The top part of each page contains a set of buttons, combo boxes,
entry fields, ... which give fast and intuitive access to the most
commonly used switches for that tool.
- Textual selection of switches
- The bottom part is an editable entry field, where you can directly
type the switches. This makes it easier to move from
an older setup (e.g. Makefile, script) to GPS, by copy-pasting switches.
The two parts of the pages are kept synchronized at any time: clicking on a
button will edit the entry field to show the new switch; adding a new switch by
hand in the entry field will activate the corresponding button if there is one.
Any switch can be added to the entry field, even if there is no corresponding
button. In this case, GPS will simply forward it to the tool when it is called,
without trying to represent it graphically.
6.8. The Project Dependencies Editor
You can edit the dependencies between projects through the contextual menu
in the Project View.
This view makes it easy to indicate that your project depends on external
libraries, or other modules in your source code. For instance, you can give
access to the GtkAda graphical library in your project by adding a project
dependency to gtkada.gpr, assuming GtkAda has been installed in your system.
The dependencies also determine in what order your application is built. When
you compile a project, the builder will first make sure that the projects it
depends on are up-to-date, and otherwise recompile them.
When you select that contextual menu, GPS will open a dialog that allows you to
add or remove dependencies to your project. New dependencies are added by
selecting a project file name from one of several sources:
One of the loaded project from the current project tree
One of the predefined projects
These are the projects that are found in one of the directories referenced in
the ADA_PROJECT_PATH environment variable. Typically, these include third
party libraries, such as GtkAda, win32ada, ...
A new project created through the project wizard
Any project file located on the disk
In all these cases, you will generally be able to choose whether this should be
a simple dependency, or a limited dependency. The latter allows you to have
mutually dependent projects (A depends on B, which in turns depends on A even
indirectly), although you cannot reference the attribute of such a project in
the current project (for instance to indicate that the compiler switches to use
for A are the same as for B – you need to duplicate that information).
In some cases, GPS will force a limited dependency on you to avoid loops in the
dependencies that would make the project tree illegal.