Debug Menu
The Debug menu provides an interface to the graphical M-file Debugger. These topics contain instructions for debugging in MATLAB:
About the Debugger
The MATLAB Debugger helps you identify programming errors in your MATLAB code. Using the Debugger, you can:
MATLAB's Debugger has a graphical user interface and provides a command line interface as well.
About Breakpoints
The Debugger allows you to set and clear breakpoints, specific lines in an M-file at which execution halts. It also lets you change workspace contexts, view the function call stack, and execute the lines in an M-file one by one.
Note
The M-file breakpoint information is closely associated with the copy of the M-file that MATLAB holds in memory. If you clear the M-file by editing or by issuing clear Mfile, all of Mfile's breakpoints are also cleared.
Starting Debugging
To start debugging:
Note
When you run the Editor/Debugger without MATLAB open, it becomes a pure text editor; you cannot use it as a debugger.
Debugger Toolbar Buttons
Toolbar Button
|
Purpose
|
Description
|
Equivalent Command
|
|
Set/Clear Breakpoint
|
Set or clear a breakpoint at the line containing the cursor.
|
dbstop/dbclear
|
|
Clear All Breakpoints
|
Clear all breakpoints that are currently set.
|
dbclear all
|
|
Step In
|
Execute the current line of the M-file and, if the line is a call to another function, step into that function.
|
dbstep in
|
|
Single Step
|
Execute the current line of the M-file.
|
dbstep
|
|
Continue
|
Continue execution of M-file until completion or until another breakpoint is encountered.
|
dbcont
|
|
Quit Debugging
|
Exit the debugging state.
|
dbquit
|
Right-click in the Editor window to see a pop-up menu of some of the options.
Note
The Debugger's Breakpoints menu also lets you halt M-file execution if your code generates a warning, error, or NaN or Inf value.
Debugger Notations
(
) indicates that a breakpoint is set at that line. If the line selected for a breakpoint is not a valid executable line, then the breakpoint is set at the next executable line.
(
) shows the next line to execute when execution of an M-file pauses at a breakpoint.
(
) indicates a pause at the end of the script or function so you can examine variables before returning to the calling function.
Evaluating Variables
You can check values of variables from the Debugger. Highlight the text of each variable and right-click to bring up the context menu and choose Evaluate Selection. Or, alternatively, choose Evaluate Selection from the View menu. Both the selection and the result are displayed in the Command Window.
Changing Workspace Context
Use the Stack pull-down menu in the upper-right corner of the Debugger window to change workspace contexts:
Check the workspace context using whos or the graphical Workspace Browser. The variables you have created show up in the listing.
Select Continue from the Debug menu to continue executing the M-file.
Ending a Debug Session
Select the Exit Editor/Debugger from the File menu to end the debugging session.
Debugging from the Command Line
The MATLAB debugging commands are a set of tools that allow you to debug your M-files from the command line. The most general form for each debugging command is shown below.
Description
|
Syntax
|
Set breakpoint.
|
dbstop at line_num in file_name
|
Remove breakpoint.
|
dbclear at line_num in file_name
|
Stop on warning, error, or NaN/Inf generation.
|
dbstop if warning
error
naninf
infnan
|
Resume execution.
|
dbcont
|
List function call stack.
|
dbstack
|
List all breakpoints.
|
dbstatus file_name
|
Execute one or more lines.
|
dbstep nlines
|
List M-file with line numbers.
|
dbtype file_name
|
Change local workspace context (down).
|
dbdown
|
Change local workspace context (up).
|
dbup
|
Quit debug mode.
|
dbquit
|
K>> prompt. At this prompt, you can type standard MATLAB commands. When you're finished, type dbcont to resume execution.
Note
On some platforms, a debugging window may automatically appear when a function stops at a breakpoint.
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