1 <!-- ============= Debugging ====================== -->
2 <chapter id="debugging">
3 <title>Debugging</title>
5 <emphasis>To debug is human. To fix it is divine...</emphasis>
8 Well, the <emphasis>human</emphasis> part is what this section is about. The
9 <emphasis>divine</emphasis> part is up to you!
12 When a program does not behave in the way it is supposed to, we say the program
13 contains a bug or bugs. This does not refer to compilation errors — those are
14 simply errors and they are relatively easy to clear, because the compiler tells you
15 where the problems are. On the other hand, <emphasis>bugs</emphasis> are errors
16 that happen during the execution of the program and they can be hard (sometimes very hard!)
20 Any program that you think is bug-free is never completely bug-free. All we can try
21 to do is to reduce the number of bugs contained in the program. The process of removing
22 bugs is known as <emphasis>debugging</emphasis>, and the tool that is used for debugging
23 is called the <emphasis>debugger</emphasis>. <application>Anjuta</application> provides a
24 very user-friendly and powerful debugging environment (actually, a GUI wrapper over
25 <application>gdb</application>, a powerful command line debugging tool and standard on Linux).
28 A debugger tracks and traces the execution of the program and provides various
29 views of information needed to study the execution of the program.
34 The debugger has been heavily changed since anjuta 2.0.2. Some features have
35 been dropped but will be reenabled, a few have been added.
39 <!-- Debugger: Start and stop -->
41 <sect1 id="debugger-session">
42 <title>Start and stop</title>
45 There are two ways to start the debugger:
47 <listitem><para><emphasis>Running an executable</emphasis></para></listitem>
48 <listitem><para><emphasis>Attaching to a process</emphasis></para></listitem>
52 <sect2 id="debug-run">
53 <title>Running an executable</title>
56 <menuchoice><guisubmenu>Debug</guisubmenu><guimenuitem>Run Target…</guimenuitem></menuchoice>
57 to display a dialog box where you can select
58 the executable that you want to debug, the command line parameters
59 and if you want a terminal or not. The popup menu of the target combo box
60 is already filled with all executables of the current project, so you can easily
61 select one of them. But it is not mandatory, you can select any other executable.
62 The debugger accepts libtool executable, I mean script wrapping the real
63 executable generated by libtool. When you have set everything you can click on
64 <guibutton>Execute</guibutton>
65 to start the debugger, load your program and stop at its beginning.
69 In order to better user the debugger, it is recommended to debug program
70 with debugging information (-g for gcc) and no optimization (-O0 for gcc).
75 <sect2 id="debug-attach">
76 <title>Attaching to a Process</title>
78 It is also possible to attach to a running process for debugging. Choose the menu item
79 <menuchoice><guisubmenu>Debug</guisubmenu>
80 <guimenuitem>Attach to Process …</guimenuitem></menuchoice>. A list of all the
81 process running on the system will appear.
84 <title>Attach to Process dialog</title>
86 <screeninfo>Attach to Process dialog</screeninfo>
87 <graphic fileref="figures/attach.png" format="PNG" srccredit="andyp"></graphic>
91 Select the process to attach to and click <guibutton>OK</guibutton>.
95 It is currently not possible to load symbol information for the attached
101 <sect2 id="debug-restart">
102 <title>Restarting an executable</title>
104 After running a executable at least one time, you can
105 choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
106 <guimenuitem>Restart Target</guimenuitem></menuchoice> to restart your program.
107 It is just a shortcut that will stop the debugger if it is currently running
108 and restart it with the last executable.
112 <sect2 id="debug-stop">
113 <title>Stopping the Debugger</title>
115 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
116 <guimenuitem>Stop Debugger</guimenuitem></menuchoice> to stop the debugger.
117 This option will kill the program which is being debugged. If the debugger has
118 been attached to a running process, it will just detach from it without killing
119 it. You will get a confirmation box if a program is currently attached or running.
125 <!-- Debugger: Execution -->
127 <sect1 id="debugger-exec">
128 <title>Execution</title>
130 Execution of a program in the debugger can be finely controlled. The program can be
131 executed in single steps, or allowed to continue until it encounters a breakpoint.
132 Executing like this is essential for tracking program behaviour. Like a video editing
133 session, the program can be executed in <emphasis>slow motion</emphasis>
134 with the ability to go forward, pause, stop, and so on.
137 The methods that can be used to execute a program in the debugger are described in
138 the next few sections.
141 <sect2 id="dbg-step-in">
142 <title>Single stepping (step in)</title>
144 Single stepping executes only one statement of the program (from the place where it
145 has stopped) and then returns control. If the statement that is executed contains one
146 or more functions, the debugger tries to step inside the functions (in the sequence in
147 which the functions are executed). Once the statement is executed and
148 control is passed back, it is possible to study the various program parameters.
151 If the program need to been started to use single stepping.
154 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
155 <guimenuitem>Step In</guimenuitem></menuchoice>
156 or click on the <guibutton>Step In</guibutton> icon in the
157 <interface>Debug toolbar</interface> to step into a program.
161 <sect2 id="dbg-step-over">
162 <title>Single stepping (step over)</title>
164 <emphasis>Step over</emphasis> is similar to <emphasis>step in</emphasis>,
165 except that it does not step inside any function in the statement being executed.
166 The statement will be executed in one go.
169 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
170 <guimenuitem>Step Over</guimenuitem></menuchoice>
171 or click on the <guibutton>Step Over</guibutton> icon in the
172 <interface>Debug toolbar</interface> to step over statements in a program.
176 If a dynamic library is loaded during the step, the program will not
177 stop at the end of the step. But it will run until it finds a breakpoint or you
183 <sect2 id="dbg-step-out">
184 <title>Single stepping (step out)</title>
186 <emphasis>Step out</emphasis> will execute the current function until it
187 returns. The program will be stopped once it exits from the function.
188 Step out is not really single stepping, because it does not only execute
189 a single statement — it executes the whole function until that
190 function returns to the calling function.
193 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
194 <guimenuitem>Step Out</guimenuitem></menuchoice>
195 or click on the <guibutton>Step Out</guibutton> icon in the
196 <interface>Debug toolbar</interface> to step out in a program.
201 <title>Run/Continue</title>
203 This option will continue the execution of the program until a breakpoint is
204 encountered, or the program exits.
207 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
208 <guimenuitem>Run/Continue</guimenuitem></menuchoice>
209 or click on the <guibutton>Run/Continue</guibutton> icon in the
210 <interface>Debug toolbar</interface> to continue the execution of a program.
214 <sect2 id="dbg-runto">
215 <title>Run To</title>
217 This option will continue the execution of the program until the line where
218 cursor is is reached.
221 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
222 <guimenuitem>Run to Cursor</guimenuitem></menuchoice>
223 or click on the <guibutton>Run to Cursor</guibutton> icon in the
224 <interface>Debug toolbar</interface> to run until the line at cursor is reached.
228 <sect2 id="dbg-stop">
229 <title>Stop Program</title>
231 While the program is running and has control, no debugging tasks can be
232 performed. To obtain control while the program is running, choose the menu item
233 <menuchoice><guisubmenu>Debug</guisubmenu>
234 <guimenuitem>Interrupt Program</guimenuitem></menuchoice> or click on the
235 <guibutton>Stop Program</guibutton> icon in the <interface>Debug toolbar</interface>.
236 This will interrupt the program and return control to the debugger.
242 <!-- ============= Debugging: Breakpoints ====================== -->
244 <sect1 id="debugging-breaks">
245 <title>Breakpoints</title>
247 When debugging a program, it is useful to be able to stop the execution of the program at
248 a particular point, so that the state of the program can be examined at that location.
249 Breakpoints enable this to happen. Breakpoints can be set at different locations in a
250 source file, and then the program is allowed to run. When a breakpoint is encountered,
251 the execution of the program is suspended, enabling expressions to be evaluated,
252 variables to be inspected, the stack trace to be studied, and so on.
255 <sect2 id="breaks-list">
256 <title>Listing Breakpoints</title>
258 The <interface>Breakpoint list window</interface> can be opened by
259 choosing <menuchoice><guisubmenu>View</guisubmenu>
260 <guimenuitem>Breakpoints</guimenuitem></menuchoice>
264 <title>Breakpoint view</title>
266 <screeninfo>Breakpoint view</screeninfo>
267 <graphic fileref="figures/brk_dlg.png" format="PNG" srccredit="andyp"></graphic>
272 <emphasis>Location</emphasis>, refers to the location of the code in the source
273 file. <emphasis>Location</emphasis> can be specified in any of the following
278 <listitem><para>File_name:Line_number</para></listitem>
279 <listitem><para>Function_name</para></listitem>
280 <listitem><para>File:Function_name</para></listitem>
284 The first one is obvious — The location refers to the line number
285 <emphasis>Line_number</emphasis> in the source file <emphasis>File</emphasis>.
286 The second refers to the first line of the function
287 <emphasis>Function_name</emphasis>. The third is similar to the second, except that
288 this notation is used where there is more than one function with the name
289 <emphasis>Function_name</emphasis> in the program. It is possible to
290 differentiate between them by providing the <emphasis>File</emphasis>, so the
291 notation refers to the function <emphasis>Function_name</emphasis> in the
292 file <emphasis>File</emphasis>.
295 Two parameters can be associated with each breakpoint:
297 <listitem><para>Break condition</para></listitem>
298 <listitem><para>Pass count</para></listitem>
302 The <emphasis>Break condition</emphasis> is a valid C
303 expression which should evaluate to a Boolean value — that is, the
304 evaluation of the expression should result in either TRUE(1) or FALSE(0).
305 If the final evaluation value is not a Boolean value, then it will be
306 appropriately type casted to a Boolean.
309 Every time the breakpoint is encountered during the execution, the break
310 condition will be evaluated. The debugger will break the execution only if
311 the evaluation results in a TRUE value, otherwise it will continue the
312 execution as though there had been no breakpoint.
315 The default value of <emphasis>Break condition</emphasis> is always TRUE.
316 The debugger will break the execution at the breakpoint location.
319 The <emphasis>Pass count</emphasis> is an integer (unsigned) value which
320 tells the debugger to skip the breakpoint that number of times before it
321 is considered. <emphasis>Pass count</emphasis> has a higher priority than
322 the <emphasis>Break condition</emphasis>. Only when the
323 <emphasis>Pass count</emphasis> reaches zero will the debugger evaluate the
324 <emphasis>Break condition</emphasis> (if any condition is present). If there
325 is no condition, the debugger will break the execution once the
326 <emphasis>Pass count</emphasis> counts down to zero.
329 The default value of the <emphasis>Pass count</emphasis> is zero. The
330 breakpoint will be considered when it is first encountered.
334 All breakpoints are kept across anjuta session even if they correspond to
335 a non existing place. The interface try to set them each time the program
336 is started or a new dynamic library is loaded.
341 <sect2 id="breaks-set">
342 <title>Adding or Setting Breakpoints</title>
344 Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
345 <guimenuitem>Add Breakpoint…</guimenuitem></menuchoice>
346 or <menuchoice><guimenuitem>Add Breakpoint…</guimenuitem></menuchoice>
347 in the breakpoint list popup menu to open the add breakpoint dialog.
351 <title>Breakpoint add dialog</title>
353 <screeninfo>Breakpoint add dialog</screeninfo>
354 <graphic fileref="figures/brk_add.png" format="PNG" srccredit="mkv"></graphic>
359 Enter the location at which to set the breakpoint. Optionally, enter
360 the <emphasis>Break condition</emphasis> and the <emphasis>Pass count</emphasis>
361 in the appropriate entry boxes. Click <guibutton>OK</guibutton> to set the
365 A breakpoint may also be by selecting a line in the editor
366 and choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
367 <guimenuitem>Toggle Breakpoint</guimenuitem></menuchoice>, the editor popup
369 <menuchoice><guimenuitem>Toggle Breakpoint</guimenuitem></menuchoice>
370 or the <guibutton>Toggle Breakpoint</guibutton> icon in the
371 <interface>Debug toolbar</interface>.
375 Breakpoints can be added even if the debugger is not started or in dynamic
376 library not loaded yet. But they cannot be added while a program is running
377 under control of the debugger.
382 <sect2 id="breaks-edit">
383 <title>Editing Breakpoints</title>
385 It is possible to change the condition of a breakpoint of the pass count by
386 selecting the breakpoint to edit in the breakpoint list and click in the
387 popup menu item <menuchoice><guimenuitem>Edit Breakpoint</guimenuitem></menuchoice>.
390 Edit the entries as required and click on <guibutton>OK</guibutton> to
395 <sect2 id="breaks-del">
396 <title>Deleting Breakpoints</title>
398 Select the breakpoint to delete in the breakpoint list view and click on
399 <menuchoice><guimenuitem>Remove Breakpoint</guimenuitem></menuchoice>.
402 A existing breakpoint may also be deleted by selecting the line in the editor
403 and choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
404 <guimenuitem>Toggle Breakpoint</guimenuitem></menuchoice>,
405 the editor popup menu item
406 <menuchoice><guimenuitem>Toggle Breakpoint</guimenuitem></menuchoice>
407 or the <guibutton>Toggle Breakpoint</guibutton> icon in the
408 <interface>Debug toolbar</interface>.
412 <sect2 id="breaks-enbdis">
413 <title>Enabling or Disabling Breakpoints</title>
415 Click on the Enable column of the <interface>Breakpoint list window</interface> or
416 in the menu item <menuchoice><guimenuitem>Enable Breakpoint</guimenuitem></menuchoice>
417 to enable or disable the selected breakpoint.
418 The breakpoint will be enabled or disabled, depending on the current state.
421 To disable all breakpoints, click on <menuchoice><guisubmenu>Debug</guisubmenu>
422 <guimenuitem>Disable All Breakpoints</guimenuitem></menuchoice> or on
423 <menuchoice><guimenuitem>Disable All Breakpoints</guimenuitem></menuchoice> in
424 the breakpoint list popup menu.
429 <!-- ============= Debugging: Expressions ====================== -->
430 <sect1 id="debugging-expr">
431 <title>Expressions</title>
433 <sect2 id="var-local">
434 <title>Listing local variable</title>
436 When a program is running under the control of the debugger, the
437 <interface>Locals list window</interface> can be opened by
438 choosing <menuchoice><guisubmenu>View</guisubmenu>
439 <guimenuitem>Locals</guimenuitem></menuchoice>
442 Local variables of the current frame (the current funtion in which the program control
443 is present) are displayed in the <interface>Locals list window</interface>.
444 During execution of the program (eg. during single stepping), local
445 variables will be updated. If any varialble value was changed in the last debugging step, its
446 value will be highlight in red. The variables are presented in a tree form for easy
449 <title>Local variables</title>
451 <screeninfo>Local variables</screeninfo>
452 <graphic fileref="figures/local_variables.png" format="PNG" srccredit="naba"></graphic>
457 The value of a local variable can be modified by selecting it and clicking in
462 Gdb is more and more often used as a back end for a graphical front end. It
463 has been improved recently in this area. It is recommanded to use the latest
464 version (6.6) of gdb. On older version, gdb can crash when the front end
465 ask for an pointer with an invalid (but not used) value.
470 <sect2 id="var-watch">
471 <title>Listing watched expressions</title>
473 Inspecting or evaluating an expression provides the result only once. To continuously
474 monitor some variables or expressions, use <emphasis>expression watch</emphasis>.
477 Choose the menu item <menuchoice><guisubmenu>View</guisubmenu><guimenuitem>Watch
478 Window</guimenuitem></menuchoice> to display the <interface>expression watch window</interface>.
482 <sect2 id="watch-add">
483 <title>Adding an expression to watch</title>
485 Right-click on the <interface>expression watch window</interface>
486 to open the <interface>Operation menu</interface>. Choose the
487 menu item <guimenuitem>Add Watch…</guimenuitem>. Alternatively, you can
488 use <menuchoice><guisubmenu>Debug</guisubmenu>
489 <guimenuitem>Add Watch…</guimenuitem></menuchoice>
490 A dialog prompting for the expression will appear. Enter the expression and
491 click <guibutton>OK</guibutton>.
494 By default watch expression are updated automatically
495 each time the program is stopped. This can be changed in the add watch dialog
496 or later using the <guimenuitem>Automatic update</guimenuitem> menu item in the
497 <interface>expression watch window</interface> popup menu. A watched expression
498 can be update manually by choosing
499 <guimenuitem>Update Watch</guimenuitem> or <guimenuitem>Update All</guimenuitem> in
503 It is not necessary to have the debugger running to add a new watch expression.
504 If the debugger is not running or the corresponding expression cannot be found,
505 the front end will try to create the watch expression, each time the program
510 <sect2 id="watch-remove">
511 <title>Removing an expression from watch</title>
513 Select the watch expression that you want to remove in the <interface>expression watch
514 window</interface>, then open the <interface>Operation menu</interface>, clicking
515 with the right mouse button, and choose the
516 menu item <guimenuitem>Remove</guimenuitem> to remove it.
519 All watch can be removed by choosing <guimenuitem>Remove All</guimenuitem> in the
520 popup menu of the <interface>expression watch window</interface>.
524 <sect2 id="expr-eval">
525 <title>Evaluating expressions</title>
527 When control is returned from a program — possibly at a breakpoint —
528 it is possible to evaluate expressions or inspect the values of variables in the
529 program. Choose the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
530 <guimenuitem>Inspect/Evaluate …</guimenuitem></menuchoice>,
531 <menuchoice><guimenuitem>Inspect/Evaluate …</guimenuitem></menuchoice>
532 in the popup menu of the editor or click
533 the <guibutton>Inspect</guibutton> button on the <interface>Debug Toolbar</interface>.
536 A window will appear showing the result of the evaluation.
539 If an expression is highlighted in the editor, it is already displayed else
540 the window is empty. In both cases, you an select a new expression by clicking
541 on the name column and writing the new expression.
544 The expression can be added directly in the list of watched expressions by
545 clicking on <guibutton>Add</guibutton> button.
551 <!-- ============= Debugging: Program Stack ====================== -->
552 <sect1 id="debugging-stack">
553 <title>Stack Trace and Thread</title>
555 <sect2 id="stack-win">
556 <title>Stack Window</title>
558 The <interface>Stack trace window</interface> shows the contents of the
559 program stack. It lists all of the functions and their arguments in the
560 sequence they were called. There is also a number representing each call.
561 This number is called the <emphasis>Frame</emphasis>. Each call in the trace
562 exists in a different frame. This starts from frame 0 (the last function
563 called) and grows higher as the function nesting become deeper.
566 Choose the menu item <menuchoice><guisubmenu>View</guisubmenu><guimenuitem>Program
567 Stack</guimenuitem></menuchoice>, to open the stack trace for the program
572 <title>Stack trace window</title>
574 <screeninfo>Stack trace window</screeninfo>
575 <graphic fileref="figures/stack.png" format="PNG" srccredit="andyp"></graphic>
580 A small arrow points to the currently selected frame in the stack trace. By
581 default, this will be frame 0, the last function called. All of the evaluation
582 and inspection of expressions or variables will be with reference to this selected
583 frame. The scope of the variables or expressions being evaluated will be limited
584 to the selected frame only. The same applies for new expressions only in the watch.
588 <sect2 id="stack-frame">
589 <title>Setting the current frame</title>
591 Double-clicking on any frame in the stack trace will set that frame as the
592 currently selected frame (the arrow will point to the frame, indicating that it
593 has been selected as the current frame). Alternatively, open the
594 <interface>Operation menu</interface> by right-clicking on the
595 <interface>Stack trace window</interface>, and choose the menu item
596 <guimenuitem>Set frame</guimenuitem> to set the frame.
599 Changing the stack frame will change the <interface>Locals list window</interface>
600 content, but not the <interface>expression watch window</interface> as each
601 expression is evaluated in the frame used when it was defined.
605 <sect2 id="thread-win">
606 <title>Thread Window</title>
608 The <interface>Thread window</interface> show all threads used by the program
609 and display the current thread. Choose the menu item <menuchoice><guisubmenu>View</guisubmenu>
610 <guimenuitem>Thread</guimenuitem></menuchoice>, to open this window.
613 A small arrow points to the current thread. When the
614 programm is stopped, it correspond to the thread which has been interrupted.
615 Each thread has its own stack frame,so changing the current thread will change
616 the current stack frame.
620 <sect2 id="set-thread">
621 <title>Setting the current thread</title>
623 Double-clicking on any thread in the thread list will set that thread as the
624 currently selected thread (the arrow will point to the thread, indicating that it
625 has been selected as the current thread). Alternatively, open the
626 <interface>Operation menu</interface> by right-clicking on the
627 <interface>Thread list window</interface>, and choose the menu item
628 <guimenuitem>Set thread</guimenuitem> to set the thread.
631 Changing the thread will change the value of CPU registers and the current
632 stack frame, so the <interface>Locals list window</interface> will change too.
637 <!-- ============= Debugging: CPU ====================== -->
638 <sect1 id="debugging-cpu">
641 <sect2 id="cpu-regs">
642 <title>Register window</title>
644 It is possible to examine the contents of the internal registers of the
645 CPU (microprocessor). Choose the menu item <menuchoice><guisubmenu>View</guisubmenu>
646 <guimenuitem>Registers</guimenuitem></menuchoice>. A window listing all
647 of the available registers in the microprocessor and their corresponding contents
651 If any register value was changed in the last debugging step, its
652 value will be highlight in red. It is possible to change one register value
653 by selecting it and clicking in the value column.
657 <sect2 id="cpu-memory">
658 <title>Memory window</title>
660 Choose the menu item <menuchoice><guisubmenu>View</guisubmenu><guimenuitem>Memory
661 </guimenuitem></menuchoice>, to open the <interface>memory window</interface>
662 for the program being debugged. This window shows the contents of all memory.
665 The first is the memory address in hexadecimal, the second is the memory content
666 in hexadecimal too and the last column is the memory content in ascii.
669 The addressing space of even a 32 bits microprocessor is quite big(4 Giga bytes),
670 so it is very difficult to go to a particular address with the scrollbar. But
671 you can click on the right mouse button, get a new menu and select
672 <menuchoice><guimenuitem>Goto address</guimenuitem></menuchoice> to get
673 a small edit box where you can enter an address in hexadecimal.
677 <sect2 id="cpu-disassembly">
678 <title>Disassembly window</title>
680 Choose the menu item <menuchoice><guisubmenu>View</guisubmenu><guimenuitem>Disassembly
681 </guimenuitem></menuchoice>, to open the <interface>disassembly window</interface>
682 for the program being debugged.
686 The first column is the address in hexadecimal. In the second column, you can
687 have a label starting at the beginning of the line and ended with a colon or
688 a assembler instruction starting after 4 space characters.
691 Again, as the addressing space is very big, the scrollbar is quite useless.
692 You can click on the right mouse button, get a new menu and select
693 <menuchoice><guimenuitem>Goto address</guimenuitem></menuchoice> to get
694 a small edit box where you can enter an address in hexadecimal. The position
695 in the disassembly window will be changed to the program counter value when
696 the program is stopped.
701 <!-- Debugger: Others-->
702 <sect1 id="debugger-others">
703 <title>Others</title>
706 There are a number of other debugger features used less frequently and not
707 very well integrated in the new front end but which are still working.
710 <sect2 id="dbg-dyna-libs">
711 <title>Dynamically loaded Libraries</title>
713 To obtain a list of the dynamic libraries used by the program, choose the
714 menu item <menuchoice><guisubmenu>Debug</guisubmenu><guisubmenu>Info</guisubmenu>
715 <guimenuitem>Shared Libraries</guimenuitem></menuchoice>. This will bring
716 open a window which will list all the shared libraries the program has loaded
717 and their locations in the memory. It also shows whether the symbol table is
718 loaded or not (Yes/No).
722 <title>Shared Libraries window</title>
724 <screeninfo>Shared Libraries window</screeninfo>
725 <graphic fileref="figures/sharedlibs.png" format="PNG" srccredit="andyp"></graphic>
731 <sect2 id="dbg-signal">
732 <title>Kernel Signals</title>
734 Kernel signals are a way of signaling between processes in Linux. The list
735 of signals available for a program can be displayed by choosing the menu item
736 <menuchoice><guisubmenu>Debug</guisubmenu><guisubmenu>Info</guisubmenu><guimenuitem>Kernel Signals</guimenuitem></menuchoice>.
737 A window will open which lists all of the signals available in the system along with
738 a brief description of each signal.
742 <title>Kernel Signals window</title>
744 <screeninfo>Kernel Signals window</screeninfo>
745 <graphic fileref="figures/signals.png" format="PNG" srccredit="andyp"></graphic>
750 There are three columns which specify what to do when the signal is received:
755 <para><emphasis>Stop</emphasis> — this tells the debugger whether to
756 stop the program execution (and return control) when the program receives
761 <para><emphasis>Print</emphasis> — this tells the debugger whether to
762 display the received signal.
766 <para><emphasis>Pass</emphasis> — this tells the debugger whether to pass
767 the signal to the program.
773 The popup menu that is displayed when you click on the right mouse button has
774 all its item disabled because the corresponding functions are not implemented
780 <sect2 id="dbg-files">
781 <title>Information about used files</title>
783 It is possible to get some information about the files used by the debugged program.
784 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
785 <guisubmenu>Information</guisubmenu><guimenuitem>Target files</guimenuitem></menuchoice>.
786 A window will open displaying all informations.
790 <sect2 id="dbg-program">
791 <title>Information about debugged program</title>
793 It is possible to get some information about the debugged program
794 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
795 <guisubmenu>Information</guisubmenu><guimenuitem>Program</guimenuitem></menuchoice>.
796 A window will open displaying all informations.
800 <sect2 id="dbg-kernel">
801 <title>Information about kernel structure</title>
803 It is possible to get some information kernel data on the current process
804 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
805 <guisubmenu>Information</guisubmenu><guimenuitem>Kernel user struct</guimenuitem></menuchoice>.
806 A window will open displaying all informations.
810 <sect2 id="var-global">
811 <title>Information about global variables</title>
813 It is possible to list all global variables
814 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
815 <guisubmenu>Information</guisubmenu><guimenuitem>Info Global Variable</guimenuitem></menuchoice>.
816 A window will open listing all global variables.
820 <sect2 id="stack-frame-info">
821 <title>Information about the current frame</title>
823 It is possible to obtain information about the currently selected frame
824 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
825 <guisubmenu>Information</guisubmenu><guimenuitem>Info Current Frame</guimenuitem></menuchoice>.
826 A window will open describing the current frame.
830 <sect2 id="stack-arg-info">
831 <title>Information about the current function arguments</title>
833 It is possible to obtain information about the arguments of the current function
834 by choosing the menu item <menuchoice><guisubmenu>Debug</guisubmenu>
835 <guisubmenu>Information</guisubmenu><guimenuitem>Arguments</guimenuitem></menuchoice>.
836 A window will open describing the arguments.
840 <sect2 id="dbg-command">
841 <title>User command</title>
843 To send directly a command to the back end choose the
844 menu item <menuchoice><guimenu>Debug</guimenu>
845 <guimenuitem>Debugger command</guimenuitem></menuchoice>. This will bring
846 a small dialog where you can enter commands that will be send to the debugger
847 when you press <keycap>Return</keycap>.
851 The front end sends this command directly to the back end without doing any check.
852 By example if you set a breakpoint like this, it will not appear in the
853 <interface>breakpoint list window</interface>. It is better to avoid using this
854 command unless you know exactly what you are doing.