This document provides a guide through the major capabilities of the GNAT Programming Studio by working on a code example: sdc, a simple desktop calculator.
It is important to realize that the features that you are about to experiment with are available on multiple platforms, using the same user interface and capabilities, providing a user-friendly environment with a tight integration between the tools.
Start GPS in the directory containing the tutorial files, or if the directory is read-only, copy the tutorial directory and its subdirectories in a local (writable) area, and start GPS from the tutorial directory, so that GPS will load the right context.
By default, the tutorial sources can be found under
<prefix>/share/examples/gps/tutorial
, where <prefix>
is the
prefix directory of the GPS installation.
Alternatively, if you have already started GPS in another directory, you
can load the project sdc.gpr
by using the menu Project->Open...
Having launched GPS, you should now have access to a main window composed of several areas:
In the project view, open the common
directory by clicking
on the [+]
sign (a triangle under unix systems) on the left of
common
.
This will open the directory and display a list of source files located
in this directory.
Now, double click on sdc.adb: this will open a source editor on this file. The source code is syntax-highlighted: keywords, comments, strings and characters have different colors.
As with many other properties, colors are configurable in GPS:
Select the menu Edit->Preferences
. This will open a preferences
dialog window.
Select the Editor->Fonts & Colors
page by clicking on the cross next to
the item Editor
and then selecting the Fonts & Colors
item.
As you go over the various lines and labels, you will notice that by holding the mouse over a label, a tool tip pops up displaying on-line help about the selected item.
Change the background color of the Keywords
by clicking on the last
button, at the right of the Keywords
line.
Choose a color, e.g a light green. When you’re done with the color
selection, click on OK
in the color selection dialog.
Click on the Apply
button and look at the effects in the source
editor. If you like the new display, click on OK
to confirm the
changes, otherwise clicking on Cancel
will revert to the previous
color.
Select the icon Build Main: sdc.adb
on the toolbar (third icon
from the right): this will launch
a complete build of the sdc application. Note also that you can use a
key binding directly instead of this tool bar button (F4), or use the
corresponding menu item Build->Project->sdc.adb
. If you use the menu
item, an extra intermediate dialog is displayed showing the actual command
line that will be used by GPS. Pressing Enter will launch also the build.
The build has generated a number of errors in a new window: the Locations tree, displayed in the bottom area. The errors are also highlighted in the corresponding source editor.
GPS has automatically jumped to the first error message (sdc.adb, 28:6 : (style) bad indentation), at the line (28) and column (6) of the error.
Fix the error by hand by inserting a space.
Now you can fix the next error by moving the cursor to the line 30 (press the down arrow twice), and by using Ctrl-Tab (press first the Control key, and then the Tab key on your keyboard): this key combination asks the source editor to automatically re-indent the current line.
Note that on some window managers or desktop environments,
Ctrl-Tab is already defined. If this is the case, you can change this
shortcut from the key shortcuts dialog (menu Edit->Key shortcuts
,
Menus
section, /Edit/Format Selection
item).
You can then fix all the remaining errors by selecting the whole block (from line 28 to line 40) and pressing Ctrl-Tab. To select a block, you can either click on the left mouse button and select the area while holding the button, or using the keyboard by pressing the Shift key and moving the cursor using the Up or Down keys.
Press the F4 key to build again. GPS will automatically save the modified files, and start a build. This behavior (automatic saving of files before building) can be configured in the preferences dialog.
If you look at the bottom right of the GPS window, you will notice that a progress bar has appeared, displaying the current number of files compiled, and the number of remaining files. This progress bar disappears when the build is finished.
This should now report a successful build.
Now let’s try to understand a little bit about how the program is working by looking at the sdc.adb editor: there’s a loop, the main processing is done by the functions Process and Next (at line 30).
Click around line 30, move the mouse over Process
and let a tool tip
appear (Tokens.Process global procedure declared at tokens.ads:19
): this
gives information about the kind of entity and the location (file and line) of
the declaration of this procedure, the profile of the parameters, and
documentation for this function, as extracted from the comments surrounding
the procedure declaration.
Do the same for Next
(Tokens.Next global function declared at
tokens.ads:15
).
Keeping the mouse over Next
, display the contextual menu by clicking on
the right mouse button,
then click on Goto declaration of Next
: we’re now in the package
Tokens
, in file tokens.ads; but where is this file in the project?
Select the menu Navigate->Find or Replace...
: this will open a search
dialog.
In the Search for:
text entry type tokens.ads. Then
select Project view
in the Look in:
area. The search
area provides an easy way to search for text or regular expressions in
several contexts including the current file, the project view, …
Now click on Find
. The file tokens.ads, in directory struct
is highlighted.
Close the search dialog by clicking on the Close
button.
Note that in this specific case, a simpler way to locate a file in the
project view is to use the contextual menu from the source editor:
Locate in Project View: tokens.ads
.
Click on the [+]
sign (or triangle) to open tokens.ads entities.
When you click on a file in the project view, you get
language sensitive information about the file, such as
packages
, subprograms
, tasks
, ... for Ada
.
Open the subprogram
category, click on Process
: this
will open tokens.ads and move the cursor on the first line
corresponding to the procedure Process
.
Similarly, click on Next
, and move your mouse on Next
in the source editor.
Move the mouse over the Next
identifier in tokens.ads editor,
and then hold the Control key: while you’re holding the key, move the
mouse over entities: these entities now become clickable hyperlinks. Clicking
on the first mouse button will go to the declaration of the entity highlighted
(or the body if you are already on the declaration), and clicking on the
middle mouse button will go to the body directly: move
the mouse back to Next
and click. Alternatively, you can use the
the contextual menu and select Goto body of Next
; then
scroll through the procedure Next
, move the mouse on
Instructions.Read
at line 46, hold control again and
click with the middle mouse button (or from the contextual menu, select
Goto body of Read
).
We’ve now navigated quite a bit through the application source code, which you can verify by clicking on the left arrow in the tool bar, to go back to the previous locations visited.
Repeat the operation until you’re back in sdc.adb.
As with the undo/redo capability in the source editor, the
goto previous/next location
is infinite.
Go on the line 38 of sdc.adb. You can see that there is a null instruction for the case of Stack.Overflow. We are going to add some code here, using the code assist capabilities.
Type enter to create a new line, and then Scr
, and hit
Ctrl+Space.
A completion popup will be displayed, showing all the entities of the project
begining with Scr
. Select Screen_Output
. The code will be
automatically completed in the editor. Then add a dot in your code. The
completion popup will be automatically triggered, and will offer you to
complete your code with the entities contained in the Screen_Output
package. Select Msg
, add a space, and then an open parenthesis. Once
again, the completion windows will pop up, and show you the possible parameters
for msg. If you choose the first entry of the completion list
("params of Msg"), the call will
be automatically completed by a list of named parameters. Complete the list by
giving e.g. "The stack is full."
for S1
, ""
for S2
,
and True
for End_Line
.
Don’t forget to add a semicolon at the end of the instruction. Then hit F4 in order to rebuild the application.
It is now time to run the application: select the menu
Build->Run->sdc
, which will open a dialog window.
Type input.txt
in the text entry: this is the name of a text
file that will be passed as argument to the sdc program.
Now click on OK
: a new window titled Run: sdc input.txt
is created at the bottom of the main window where the sdc application
runs and displays an unexpected internal error: this is a good opportunity
to use the integrated debugger.
Close the execution window by clicking on the x icon on the top right corner of this window.
Open the preferences dialog (menu Edit->Preferences
) and
click on the Debugger
item on the left; set the button
Break on exceptions
to Enabled: this will enable by default a special
breakpoint every time an exception is raised. Click on OK
to confirm your
change.
Now select the menu Debug->Initialize->sdc
: a new window is
created: this is the debugger console.
You can also look at the various debug menu item and tool bar buttons which are
now activated.
Use the menu Debug->Data->Call Stack
: this opens a new window on the
right of the source editors. If you select the contextual menu in the call
stack, various pieces of information can be displayed or
removed in the call stack. From this contextual menu, add the
Frame Number
info by clicking on it.
Now select the menu Debug->Run...
. Notice that input.txt
has
been filled automatically for you since the two menus Build->Run...
and
Debug->Run...
are synchronized. Click on OK
: the debugger should
stop on an exception (Constraint_Error
in the file stack.adb, at
line 49).
Go up in the call stack by clicking on the tokens.process
line
(frame number 6 or 7, depending on your GNAT version).
If you move the mouse over the parameter T
at line 64, a tool tip is
displayed showing the value of T
. You have probably noticed that
tool tips, like menus, are contextual: depending on the current session and
on the entity selected, different information is displayed.
Select the contextual menu Debug->Display T
: this will open a new
window: the data window, with a box displaying graphically the contents
of the different fields of T
, each clearly separated.
On T
data display, select the contextual menu
Display->Show Value + Type
: this displays for all fields both their
type and value.
Special colors are used in the data display: blue for pointers that can be
dereferenced by a double-click (double click on T.val
); red for fields
that have been modified since last step.
From the T box, right-click to display the contextual menu and
select View memory at address of T
: a memory view is opened.
Use the up
and down
arrows on the right to visit memory.
Click in the memory dump, and modify it by typing numbers. Notice the
red color for modified values;
click on Undo Changes
to cancel the modifications;
click on Close
to close the memory window.
In the call stack, go back to stack.push
frame (num 4 or 5).
Move the mouse over Last
and let the debugger display its value: 0.
From the contextual menu, select Goto declaration of Last
: this
will jump to the line 16 of stack.adb, where you can see that
Last
is a Natural
. Now click on the Goto Previous Location
button in the tool bar: we’re now back at line 49 where we can see that for a
Push
procedure, Last
should be incremented, and not decremented.
Fix the line to Last := Last + 1;
Save the file (Ctrl-S);
End the debug session: menu Debug->Terminate
;
Rebuild (press F4 key);
Rerun (menu Build->Run->sdc
, click on OK
): the program now
completes as expected. Close the execution window.
Now go back to the file sdc.adb, move the mouse over the procedure
sdc at line 8, select the contextual menu
Browsers->Sdc calls
: this will open a new window titled
Call graph browser.
Note that there is also a top level contextual menu (Sdc calls
)
which provides a tree view of the callers/callees.
In the call graph, click on the right arrow of Process
(one of the
first items on the top). Also click on the right arrow of error_msg
.
Select Orthogonal links
in the contextual menu of the graph to change the
way links are displayed in the graph.
You may then play with the zoom (= and - keys).
If you select Hide links
from error_msg
contextual menu, this
will hide all the links that are related to this item: the link between the
callers and callees of error_msg
are no longer displayed. This can
be useful when the graph becomes complex, to hide some parts. If you go back to
the contextual menu, you can now select Show links
to show the links
again.
Click on right arrow of process
((Decl) instructions.ads:12
).
The items can also be moved: move e.g msg
item around.
You can also recompute the layout of all the current items by using
the browser’s contextual menu Refresh layout
(move the mouse on the
browser’s background, with no box underneath, and right click).
Click on left arrow of msg
to display who is calling msg
. Notice that view
calls msg
.
Click on left arrow of view
: the arrow disappears, and no
new items are created, which means that view
isn’t called by anyone,
so we’re now going to remove this procedure.
From view, click on the blue link: stack.ads:32
, this will open
the file stack.ads at line 32.
Then from the source editor (file stack.ads), select the contextual
menu References->Find all references to View
: this highlights the
Locations
tree which now contains all the references for view
,
grouped by files (stack.ads and stack.adb).
The first location is highlighted automatically: this is the spec of the
procedure View
. Now click in the tree on the +
sign (or
triangle) at the left
of stack.adb: two locations are listed, at line 90 and 97.
Click on each of these locations: they correspond to the procedure body.
The Find all references
capability is another way to list all the uses of
an entity, and it confirms that View
isn’t called in our project.
Remove View body by e.g selecting it, and pressing the Delete key, then save the file (Ctrl-S).
Do the same for the spec, save the file.
Close the stack.ads and stack.adb files (menu File->Close, or using the shortcut Ctrl-W). Rebuild by pressing the F4 key.
Let’s now see how to create a project corresponding to the sdc project we’ve used in this tutorial.
Go to the menu Project->New...
: this is a standard wizard, with various
steps listed on the left area of the window.
The first page of the wizard allows you to select what kind of project you
want to build, depending on the information you have. Select the default
choice Single Project
, and press Forward
.
Type sdc2 in the project name field.
Click on Forward
: we are now on the language selection page.
It is possible to create a multi-language project by e.g. selecting the C or C++
check box.
Click on Forward
: we are now on the VCS page
. VCS stands
for Version Control System.
GPS provides a generic framework for VCS which allows it to support
new systems easily. Systems supported by default are CVS, ClearCase,
Subversion and GIT. Select Auto
, which means that GPS will automatically
detect the version control system used, if any.
Click on Forward
: this is the source directories selection,
used to specify the project’s sources. Click on the Add
button,
and select the struct
directory, then click on OK
to validate.
Click on Forward
: this is the Build
and Exec
directory
selection, used to store object, ali files, ...
Click on the first Browse
button, then click on
obj
, and finally click on OK
.
Click on Forward
: this is the main units selection, used mainly for
building executables and debugging.
Click on Add
, open the common
directory and select
sdc.adb
.
Click on Forward
: this is the naming scheme editor.
GNAT is very flexible and can use any kind of naming scheme for Ada files.
In particular, you can easily set the default file
extensions (e.g by using one of the predefined schemes) and you
can also specify exceptions that use non standard file names.
Click on Forward
: we’re now in the switch selector.
Select Recompile if switches changed
.
Click on Ada
page.
Select Full errors
and Overflow checking
.
The boxes and the command line (the text entry at the
bottom of the page) are fully synchronized, e.g if you click on the
command line, and change -gnatf
to -gnat
, the
Full errors
check box is unselected; now type a
to get
-gnata
, and notice that Enable assertions
is now selected.
We’ve now created a project similar to the one used in this tutorial.
Click on Cancel
to close the wizard.
Clicking on Apply
instead would have created the project file
and loaded it in GPS.
In the project view, on the project sdc, use the contextual menu
Project->Properties
.
All the properties set in the project wizard can be found here as well.
You can switch between pages by clicking on the tabs located along the
left side of the window.
Once you’re done exploring the property pages, click on the Cancel
button to close the properties window.
Select the window titled "Scenario". If not available, you can open it
using the menu Tools->Views->Scenario
.
This window contains a Build
label.
This is a configuration variable. With GPS and the GNAT project facility, you can define as many configuration variables as you want, and modify any project settings (e.g. switches, sources, ...) based on the values of configuration variables. These variables can also take any number of different values.
The Build
variable demonstrates a typical Debug/Production
configuration where we’ve set different switches for the two modes.
Click on the button at the left (Edit variable properties
): this
is the variable editor, where values can be added or renamed.
Close the variable editor by clicking on the Cancel
button.
Now, let’s take a look at the switches set in the project.
Select the menu item Project->Edit File Switches
: a global
switch editor is displayed in the working area, showing the
switches associated with each file in the sdc
project.
The editor lists the switches associated with each file in the project. Gray entries indicate default (global) switches. Notice that screen_output.adb has specific switches, which are highlighted using a different font.
Switch between Debug
and Production
mode in the Build
combo box: the switches are updated automatically.
Back to our project, let’s now examine the dependencies between sources.
Select sdc.adb in the Project View
and then the contextual menu
item Show dependencies for sdc.adb
: this will open a new graph showing
the dependencies between sources of the project.
Click on the right arrow of tokens.ads to display the files that tokens.ads depends on. Similarly, click on the right arrow of stack.ads.
Back in the project view, on the Sdc project, select the contextual
menu Project->Dependencies
, then on the Add From File
,
then open the tutorial
directory and click on the projects
subdirectory. Select the file
prj1.gpr
. Click on Apply
to validate the change.
You can see the new dependency added in the project view, as a tree of
projects. In particular, project dependencies are duplicated: if you open
the prj1
icon by clicking on the [+]
sign (or triangle), and then
similarly open the prj2
icon, you will notice that the project
prj4
is displayed twice: once as a dependency of prj2
, and
once as a dependency of prj1
.
GPS can also display the graph of dependencies between projects: on Sdc
project, use the contextual menu
Show projects imported by Sdc
: this will open a project hierarchy
browser.
On the Sdc.gpr
project, select the contextual menu
Show projects imported by Sdc recursively
.
In the browser, you can move the project items, and select them to highlight the dependencies.
This terminates our tour of GPS, the GNAT Programming Studio. We hope this tutorial gave you a good overview of the general capabilities available with GPS. A non exhaustive list of the features not mentioned in this document includes:
For more information, please look at the User’s Guide (gps.html),
and also look at the Tools
menu which gives access to most of these
capabilities.
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If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances. It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice. This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. 8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS How to Apply These Terms to Your New Programs If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. <one line to give the program's name and a brief idea of what it does.> Copyright (C) 19yy <name of author> This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. <signature of Ty Coon>, 1 April 1989 Ty Coon, President of Vice This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.