Technical Solutions

Solution:

This Solution covers several debuggers on various Linux/UNIX/Mac plaforms. For other configurations, see the Debugging section of Tech Note 1605, MEX-files Guide:
http://www.mathworks.com/support/tech-notes/1600/1605.html

This solution discusses the general use of a UNIX debugger followed by step-by-step examples on how to use the various UNIX debuggers.

NOTE: These examples are for illustration purposes only. For complete instructions on how to use a specific debugger, please refer to the debugger's Reference Guide or help files.

The following section gives a generic description of how to debug C MEX-files. Complete instructions for each debugger follows this discussion.

1.Note: You must build your MEX-File with symbols. In order to do so, issue the following command at the MATLAB Command Prompt:
mex -g filename.c

or at the UNIX prompt:

unix> mex -g filename.c 

2.At the UNIX prompt, start up MATLAB with a particular debugger

unix> matlab -D<name_of_debugger> 

3.Once the debugger loads MATLAB into memory, continue running with the run command:

<debugger> run

Note: you may have to execute the following command to load the symbols for the MEX-file:

add-sym <filename>

If you are using MATLAB R12 or R12.1 please use the following instead:

<debugger> run -nojvm

4.MATLAB will now start up. You can enable MEX-File debugging with
dbmex on
% call the MEX-File as you normally would
(i.e. through an M-File or by its name.)

5.MATLAB will now tell you how to load the MEX-File. You can set breakpoints at this point.

<debugger> stop in mexFunction
<debugger> continue

6.Once you hit a breakpoint, you can use the debugger as you would normally.

<debugger> step
<debugger> step

7.If you are at the MATLAB prompt and want to return control to the debugger, issue the command
dbmex stop
As a rule of thumb, if you use the GCC C compiler, use the GCC debugger. If you use the native C compiler, use the native debugger.

The following is a list of available debuggers with the appropriate debugging commands noted. For a complete example on how to use these debuggers, please see below:

Alpha
G-gdb run, break, step, continue, quit, print, share, file
N-dbx run, stop, step, cont, quit, print, file

HP 700
G-gdb run, break, step, continue, quit, print, share, file
N-dde DDE does not allow breakpoints to be set.

IBM RS/6000
G-gdb run, break, step, continue, quit, print, share, file
N-dbx run, stop, step, cont, quit, print, file

Linux
G-gdb run, break, step, continue, quit, print, share, file

SGI
G-gdb run, break, step, continue, quit, print, share, file
N-dbx run, stop, step, cont, quit, print, file
N-cvd CVD is not supported on the SGI at this time.

SGI64
G-gdb GCC is not supported on the SGI64 at this time.
N-dbx run, stop, step, cont, quit, print, file
N-cvd CVD is not supported on the SGI64 at this time.

Sol2
G-gdb run, break, step, continue, quit, print, file
N-dbx run, stop, step, cont, quit, print, file

Sun4
G-gdb run, break, step, continue, quit, print, add-sym, file
N-dbx run, stop, step, cont, quit, print, file


Alpha

GDB:

The following are the steps you should take to debug using GDB on the Dec Alpha:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
      ($MATLAB is your MATLAB root directory)
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> share <full path to yprime.mexap> 
      i.e. /home/name/mex/yprime.mexap
<gdb>break mexFunction
<gdb> continue
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> continue 
(This should bring you to line 54 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit 

This will display the following:

The program is running.  
Quit anyway (and kill it)? (y or n) 

answer  y

DBX:

The following are the steps you should take to debug using DBX on the Dec Alpha:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx> quit

HP700

GDB:

The GDB debugger is currently not supported.

DDE:

It is currently not possible to set breakpoints when using the DDE debugger.

IBM RS 6000

GDB:

The following are the steps you should take to debug using GDB on the IBM RS 6000:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
     ($MATLAB is your MATLAB root directory)
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> share <full path to yprime.mexrs6> 
      i.e. /home/name/mex/yprime.mexrs6
<gdb> break mexFunction
<gdb> continue
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> continue 
(This should bring you to line 54 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit 

It will display the following:

The program is running.  
Quit anyway (and kill it)? (y or n) 

answer  y

DBX:

The following are the steps you should take to debug using DBX on the IBM RS 6000:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

If you are using MATLAB 6.0 (R12) or R12.1, please do the following instead:

<dbx> run -nojvm

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx>quit 

Linux

GDB:

The following are the steps you should take to debug using GDB on Linux:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
      ($MATLAB is your MATLAB root directory)
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> share <full path to yprime.mexlx> 
      i.e. /home/name/mex/yprime.mexlx
<gdb> break mexFunction
<gdb> continue
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> continue 
(This should bring you to line 54 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and bring you back to MATLAB.)

dbmex stop


<gdb> quit 

It will display the following:

The program is running.  
Quit anyway (and kill it)? (y or n) 

answer  y

SGI

GDB:

The following are the steps you should take to debug using GDB on the SGI:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
      ($MATLAB is your MATLAB root directory)
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> share <full path to yprime.mexsg> 
      i.e. /home/name/mex/yprime.mexsg
<gdb> break mexFunction
<gdb> continue
<gdb> step
<gdb> break 56  
<gdb> step
<gdb> continue 
(This should bring you to line 56 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit 

It will display the following:

          
The program is running.  
Quit anyway (and kill it)? (y or n) 

answer  y

DBX:

The following are the steps you should take to debug using DBX on the SGI:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx>quit

CVD:

Building of MEX-files with CVD on the SGI is currently not supported.

SGI64

GDB:

Building of MEX-files with GDB on the SGI64 is currently not supported.

DBX:

The following are the steps you should take to debug using DBX on the SGI64:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx>quit 

CVD:

Building of MEX-files with CVD on the SGI64 is currently not supported.

Sol2

GDB:

The following are the steps you should take to debug uisng GDB on Solaris2:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
($MATLAB is your MATLAB root directory)
unix>matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> break mexFunction
<gdb> continue
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> continue 
(This should bring you to line 54 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit 

It will display the following:

The program is running.  
Quit anyway (and kill it)? (y or n) 

answer  y

DBX:

The following are the steps you should take to debug using DBX on Solaris2:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx> quit 

Sun4

GDB:

The following are the steps you should take to debug uisng GDB on the Sun4:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
($MATLAB is your MATLAB root directory)
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> add-sym <full path to yprime.mex4> address number 
i.e. (/home/name/mex/yprime.mex4)  
NOTE: The debugger will tell you what the address number 
is and what exactly you should type at this point.
<gdb> break mexFunction
<gdb> continue
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> continue 
(This should bring you to line 54 in yprime.c)
<gdb> step
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> continue 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit 

It will display the following:

The program is running. 
Exit anyway? (y or n) 
answer  y

DBX:

The following are the steps you should take to debug using DBX on Sun4:

unix> mex -g yprime.c
unix> matlab -Ddbx
<dbx> run

dbmex on
yprime(1,1:4)


<dbx> stop in mexFunction
<dbx> cont
<dbx> step
<dbx> stop at 54  
<dbx> step
<dbx> cont 
(This should bring you to line 54 in yprime.c)
<dbx> step
<dbx> print r2 
(You should see the value of r2 printed to screen.)
<dbx> step
<dbx> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<dbx> quit

Mac

GDB:

The following are the steps you should take to debug using GDB on Mac:

unix> mex -g -f $MATLAB/bin/gccopts.sh yprime.c 
unix> matlab -Dgdb
<gdb> run

dbmex on
yprime(1,1:4)


<gdb> share <full path to yprime.mexmac>
(i.e. /home/name/mex/yprime.mexmac)
<gdb> break yprime.c:mexFunction
<gdb> cont
<gdb> step
<gdb> break 54  
<gdb> step
<gdb> cont 
(This should bring you to line 54 in yprime.c)
<gdb> print r2 
(You should see the value of r2 printed to screen.)
<gdb> cont 
(Should finish running yprime and 
bring you back to MATLAB.)

dbmex stop


<gdb> quit

It will display the following:

The program is running. 
Exit anyway? (y or n) 

answer y