SDB User’s Guide

Version 1.0

Feb. 17, 1999

The Spruce Fir Moss Spider Debugger (SDB) is a debugger for programs developed with the Titanium reference compiler (tc/tcbuild). Based upon gdb v4.17, this debugger retains all of the original’s functionality in debugging various languages, platforms, and thread packages. Additional support was added to simplify debugging Titanium programs, such as accessing Java and Titanium arrays as well as displaying Domains, RectDomains, and Points.

Currently some features of Titanium cannot be debugged with this implementation. These will be addressed soon. They include debugging wide pointers (NOW, smp-wide), modifying variables on the fly, calling functions in the executable from the command line, and runtime type casting when printing variables.

Gdb supports cross language debugging though language commands and vaious language specifications built into it. A new gdb language type called titanium has been added. When Titanium programs are debugged, the debugger language is automatically set to this value. Once the debugger language is set for Titanium, the command line behaves like a mini-interpreter. So, a subset of the commands in the Titanium language is available. One can access arrays and variables (formals, automatics, and object fields) in the same format as in the Titanium language itself. Additionally, the command line supports creating Titanium Point<N> classes in the debugger to more easily access arrays.

The debugger currently works with the uniproc (the default), smp-narrow, and pthread backends of the Titanium compiler’s runtime systems. Sdb will debug the latter two only if gdb 4.17 supports the debugging of threads—currently includes Sparc Solaris. A version for Linux threads is forthcoming.

No additional commands have been added. Multi-programming is supported through gdb’s thread commands. Some Titanium specific commands, however, will be added to better support multiprogramming.

Titanium processes on the supported backends use thread libraries. So, debugging multiple processes is available only if debugging threads is available on your platform. Sdb is based upon a version of Gdb 4.17 that supports debugging threads on (at least) Solaris and Linux platforms. On Linux platforms, please consult the URL:

to verify that you have the supported library versions.

First, you need to build your Titanium program with the –g option to turn on support for debugging and also (recommended) turn off optimizations with "dash Oh-Zero".

$ tcbuild --tc-flags "-O0" –g myProgram.ti

$ gdb myProgram

SPRUCE-FIR MOSS SPIDER Debugger sdb 0.01

[ … ]

(sdb)

(sdb) show language

The current source language is "auto; currently titanium".

(sdb) set language titanium

(sdb)

(sdb) break main

Breakpoint 1 at 0x338b4: file myProgram.ti, line 16.

(sdb) run

Starting program: myProgram

Breakpoint 1, Main.main (args=0x197f80) at myProgram.ti:16

16. int aNumber;

(sdb)

Set a breakpoint based on the file name and line number and continue to skip over the initializations

(sdb) break myProgram.ti:33

Breakpoint 2 at 0x33dd0: file myProgram.ti, line 33.

(sdb) continue

Continuing.

Breakpoint 2, Main.main (args=0x197f80) at myProgram.ti:33

33. aPoint = [2];

(sdb)

Display some program values.

(sdb) print aNumber

$1 = 5

(sdb) print object

$2 = (MyClass) 0x1a16a8 (java.lang.Object.PrivateInfo = 0,

MyClass.x = 1, MyClass.y = 2)

(sdb) print object.x

$3 = 1

(sdb)

Look at the Java array created and index its values.

(sdb) print java_array

$4 = (int []) 0x19dd98 int[5]

(sdb) print java_array[2]

$5 = 2

(sdb)

Do the same for the Titanium array.

(sdb) print ti_array

$6 = (MyClass [1d]) 0xeffff8a8 MyClass[[[1]:[5]:[1]]]

(sdb) print ti_array[[5]]

$7 = (MyClass) 0x1a1600 (java.lang.Object.PrivateInfo = 0,

MyClass.x = 1, MyClass.y = 2)

(sdb)

Notice that if you give an out-of-bounds access, the debugger will catch it.

(sdb) print java_array[200]

Index value of 200 is out of bounds while accessing a Java array of size 5

(sdb)

(sdb) step

35 System.out.println("Done.");

(sdb) print ti_array[aPoint]

$8 = (MyClass) 0x1a1648 (java.lang.Object.PrivateInfo = 0,

MyClass.x = 1, MyClass.y = 2)

(sdb)

Finally, complete the execution and quit.

(sdb) continue

Continuing.

Done.

Program exited normally.

(sdb) quit

Currently, the smp-narrow (and likely the pthread) backends of the Titanium compiler are supported by Sdb for multiprogramming. These backends use either the Solaris or pthread packages for Titanium processes. Information about the threads can be gotten from the info command.

If, for example, a program had two processes, you may see (from a Solaris OS using the smp-narrow backend):

(sdb) info threads

12 Thread 5 (LWP 4) Main.main (args=0x1caf00) at myProgram.ti:16

11 Thread 4 0xef77759c in _swtch ()

10 Thread 3 (LWP 2) 0xef6b9838 in _signotifywait()

9 Thread 2 0xef77759c in _swtch ()

8 Thread 1 0xef6b96f0 in _lwp_sema_wait ()

* 7 Thread 6 (LWP 5) Main.main (args=0x1caf10) at myProgram.ti:16

[ … stuff about LWPs … ]

(sdb)

This shows the two Titanium process threads—Thread 5 and Thread 6. The other entries can be ignored. Because the threads are created in order of process numbers, Thread 5 is Titanium process 0, while Thread 6 is process 1. The * next to the 7 indicates that Thread 6 (Titanium process 1) is the current thread being viewed.

To see what is happening with Titanium process 0, switch the current thread using the thread command.

(sdb) thread 12

[Switching to Thread 5 (LWP 4)]

#0 Main.main (args=0x1caf00) at myProgram.ti:16

16 int aNumber;

(sdb)

Future versions of Sdb will have specific command to help in this process.