Debugging with GDB Manual
Page
Table of Contents
Stack frames
Continuing and stepping Signals
Print settings Value history
Breakpoints
Examining the Symbol Table
Specifying a Debugging Target
Commands for heap profiling
Stop when freeing unallocated or deallocated blocks
Scramble previous memory contents at malloc/free calls
Batch Mode
Example Illustrating Execution Path Recovery
Support for the info target Command
Support for the dumpcore command
Enhancements to the dumpcore command
Detecting memory leaks using GDB under Aries
Command for evaluating the address of an expression
Support for steplast command for C and C++
Debugging the application using GDB under Aries
HP-UX Terminal User Interface
Command files 289 Commands for controlled output 290
Miscellaneous commands 265 16.3
Setting Command History Feature in GDB 281 17.4
User-defined commands 287 18.2
304
20.7 Errors 302 20.8
22.2 How to report bugs 361
20.9 Invalidation notices 303
List of Tables
List of Examples
Summary of GDB
Free Software
Contributors to GDB
Page
Contributors to GDB
Page
Let us use GDB to try to see what is going on
Sample GDB Session
Loading the Executable
Running the executable under GDB
Setting Display width
Setting Breakpoints
Here we describe how to set a breakpoint
Stepping into a subroutine
Examining the Stack
Printing Variable Values
Listing Source Code
Setting Variable Values During a Session
Gdb c Continuing Definebaz,defnQUOTEfooUNQUOTE Baz
Page
Invoking GDB
Getting In and Out of GDB
Files
Choosing files
Choosing modes
Processed. See Command files
Like two `\032 characters, followed by the file name
GNU Emacs sets this option when it runs GDB as a
Line number in a standard, recognizable fashion each
Time a stack frame is displayed which includes each
Emacs
Quitting GDB
Redirecting WDB input and output to a file
Interface
Shell commands
Page
GDB Commands
Command syntax
Command completion
GDB sounds bell press TAB again, to see
Short list of named classes of commands
Getting help
Help , h
This is intended for use by GNU Emacs
Apropos reload
Results
Complete
Getting help
Page
Arguments, so that you may use normal
Running Programs Under GDB
Compiling for debugging
Starting your program
See Arguments To Your Program
Your program. SeeProgram Environment
Directory
Arguments To Your Program
Program Environment
Program. See Program Input and Output
Do not supply varname, print the names
For example, this command
Display the list of search paths for executables
Path environment variable
Program Input and Output
Working directory
Debugging a Running Process
Killing the child process
Debugging programs with multiple threads
New process 35 thread
Display a summary of all threads currently
Here are commands to get more information about threads
Thread apply command allows you to
With the command argument threadno
Debugging programs with multiple processes
Fork. The child process runs
New process. The mode can be
Unimpeded. This is the default
Set the debugger response to a program call
Breakpoints
Stopping and Continuing
Setting breakpoints
Breakpoints
See Break conditions page 59, for more
Breakpoint is
Breakpoint
Catchpoint
Whether
Breakpoints are
When hit
Enabled
Marked to be
Setting catchpoints
Shared library, or the unloading
Call to vfork. This is currently only
Is currently only available for HP-UX
Unloading of any dynamically loaded
Deleting breakpoints
Disabling breakpoints
Selecting a frame page 73 . When
Break conditions
Use condition, GDB checks expression
Breakpoint, GDB prints an error message
No symbol foo in current context
Stops your program only if the value
Breakpoint command lists
Breakpoint menus
Cannot insert breakpoints
Conditions
Continuing and stepping
Function
Setting breakpoints page 52. This form of the command
Stops. See Automatic display
Signals
Info handle is an alias for info signals
Stopping and starting multi-thread programs
Stopping and Continuing
Stack frames
Examining the Stack
Commands for Examining the Stack
Stacks Without frames
Backtraces
Selecting a frame
Information about a frame
Have existed longer. n defaults to one
When used without any argument, this command does not
With an argument, this command is used to select a stack
Setting catchpoints
Page
Show listsize
Examining Source Files
Printing source lines
List
Searching source files
Specifying source directories
Source and machine code
Show directories
Contains
Disassembling the program via
Set disassembly-flavor
Disassemble or x/i commands
Select the instruction set to use when
Page
To See Artificial arrays page 85, for more information
Following forms of print command are supported
Examining Data
Expressions
Normally supposed to reside at addr
Where it is defined. See Program variables
Program variables
Type addr
Artificial arrays
You can print the contents of array with
Output formats
Time you use either x or print
Machine instruction. The default is
Examining memory
Print, s null-terminated string, or
However, the count n must come first wx4 does not work
For fmt i or s, or including a unit-size or a number
Automatic display
For fmt specifying only a display format and not a size or
See Output formats
Print settings
Address
A symbol. This is the default
File name and line number of a symbol
Symbolic form of an address
Short strings. The default is off
Default is off
Strings. When GDB starts, this limit is set to
Setting number-of-elementsto zero
Default
This is the default format
Show which format GDB is using to print
Print using only seven-bit characters if this
Would print
These settings are of interest when debugging C++ programs
Default is on
Show whether C++ names in assembly listings
Value history
Convenience variables
Program being debugged terminates
Command, in which case it is a pointer to the type of $
Format in which the data was printed
$exitcode
Or add four to the stack pointer3 with3with
Registers
Info registers Info all-registers Info registers regname
Or print the instruction to be executed next with
This is what the macro produces
Printing Floating Point Values
Floating point hardware
To get the bit pattern, try the following macro
100
Cpp
Using GDB with Different Languages
Switching between source languages
List of filename extensions and languages
Files
Setting the working language
Not skip over function prologues when stepping
Having GDB infer the source language
Displaying the language
Type and range checking
An overview of type checking
An overview of range checking
Supported languages
C++
Types and pointer types
Expressions is 0 for false and non-zero for true
Non-zero for true
Left shift, and right shift. Defined on integral types
C++ constants
Class types
Double colons also represent the GDB scope operator see
Expressions page 83. Same precedence as , above
GDB expression handling can interpret most C++ expressions
1.3 C++ expressions
C++ defaults
Printing the variable or class returns
C++ type and range checks
See Breakpoint menus
GDB features for C++
GDB and C
Breakpoint menus
Fortran
Fortran types
Fortran types supported
Greater than or equal to
Less than
Less than or equal to
Greater than
Fortran special issues
Commonblockname
Block
Examining the Symbol Table
For example, for this variable declaration
Two commands give this output
As with whatis, using ptype without an
Symbols will be read when needed
Once. This is the default
Allow GDB to reload the symbols for
Replace symbol definitions
Do not replace symbol
Class, or union―for example, struct
Setting
Is in another source file. The default is on
Tell GDB to resolve opaque types. An opaque
Assignment to variables
Altering Execution
Stores the value 4 into that memory location
Continuing at a different address
Giving your program a signal
You can use the following command to return from a function
Returning from a function
Is used as the return value from the function value
Calling program functions
Patching programs
Return , return
Patching programs
124
GDB Files
Commands to specify files
See Optional warnings and messages
Map in symbol information from this auxiliary
Option with any of the commands that load
GDB has the entire symbol table available
Write the symbols for your program into a
Section
New library has been loaded, until the symbol
Symbols were loaded. Both the commands list
To display or set the threshold, use the commands
If threshold is nonzero, symbols from all
Megabytes
Names where the desired shared libraries reside. GDB
Searching the default system directories
Specifying shared library locations
Errors reading symbol files
Verbose on. See Optional warnings
Messages
Debug your program, though certain symbols
Symbol scope block as starting on the previous
Is the symbol type of the uncomprehended
GDB circumvents the error by ignoring this
Commands for managing targets
Specifying a Debugging Target
Active targets
See Commands to specify files
Choosing target byte order
Display GDBs current idea of the target byte order
Instruct GDB to assume the target is big-endian
Instruct GDB to assume the target is little-endian
Executable
Summary of HP Enhancements to GDB
HP-UX Configuration-Specific Information
Support for setting breakpoints using shared library name
Implementation of ask mode for set follow-fork-mode
Command watchtarget
HP-UX dependencies
Linker Dependencies
Dependent Standard Library Routines for Run Time Checking
Getpid Close Srand Strchr
Abort Unlink Atoi
Supported Platforms and Modes
GDB location
HP-UX targets
Support for Alternate root
WDB Location
Bin $WDBROOT/bin
Specifying object file directories
Librtc.sl location $WDBROOT/bin Opt/langtools/ n/a
None
Fix and continue debugging
Fix and Continue restrictions
Fix and Continue compiler dependencies
Using Fix and Continue
Example Fix and Continue session
Compile the program
Run the program
Make the necessary changes. In this case, add return total
Gdb b main
Gdb run
Gdb edit
Inline Support
Inline Debugging in HP 9000 Systems
Gdb q
Step next list backtrace frame n info locals info args
Breakpoint info frame disassembly
Following options available for the set inline-debugcommand
Inline Debugging in Integrity Systems
Debugging Inline Functions in Integrity Systems
Limitations
Info frame disassembly
Debugging Macros
Viewing and Evaluating Macro Definitions
Compiler Options to Enable Macro Debugging
Evaluating Macros
Debug=none
Examples for Macro Debugging
HP-UX Configuration-Specific Information
Debugging Memory Problems
When to suspect a memory leak
Memory debugging restrictions
Memory Debugging Methodologies
Debugging Memory in Interactive Mode
Command discards the data existing in the file
Displays all current settings for memory
This command are ignored from report. If
Heap growth. The default value is 100. Every
Debugging Memory Problems
Such as attempting to access space that is freed
Debugging when the string option is set for
Have occurred and WDB reports the problem
Specific pattern when it is allocated or
User-specified value
Use the info command to show list of memory leaks
If the user specifies a value less than 16 for
Number of bytes, the debugger ignores it
Debugging Memory in Batch Mode
Setting Configuration Options for Batch Mode
Gdb info leak
Sets the number of frames to be printed for leak context
Framecount=noframes or set heap-check frame-count noframes
For 64-bit IPF applications
For 32 bit IPF applications
For 64 bit IPF applications
For 64 bit PA applications
Ldpreload
Environment variable setting for Batch mode debugging
Stderr error message goes to stderr
Aborts execution when heap objects
Aborts execution when out of memory
Log file for batch mode must be
Example for Batch Mode RTC
Complete one of the following steps
Rtcconfig file should contain entries such as the following
Preload the librtc library as follows
Run the program as follows
For 32 bit PA applications
Specifying minimum leak size
Configuring memory debugging settings
Run the program Start a debugging session as follows
Specifying the stack depth
Specifying minimum block size
Stop when freeing unallocated or deallocated blocks
Scenarios in memory debugging
For example, if you use
Detect dangling pointers and dangling blocks
Scramble previous memory contents at malloc/free calls
Interactive debugging mode set heap-check scramble on off
Syntax
Detect in-block corruption of freed blocks
Off
Memory Debugging Commands in Interactive and Batch Mode
As the start of the heap, end of the heap, heap
Commands for heap profiling
Point you use the info heap command
Heap Profiling
Set a breakpoint
This example shows how to use this feature on HP-UX
Changes for a given run
Commands to track the change in data segment value
Support for Enabling and Disabling Specific Threads
Thread Debugging Support
Advanced Thread Debugging Support
Backtrace Support for Thread Debugging
Pre-requisites for Advanced Thread Debugging
Enabling and Disabling Advanced Thread Debugging Features
Cv-multiple-mxs onoff The set thread-check cv-multiple-mxs
Onoff command checks if an application
Unlock-not-own onoff The set thread-check unlock-not-own
Mixed-sched-policy onoff The set thread-check
Different mutexes. The debugger transfers
This returns an Einval error to
User and prints a warning message when this
Command checks if any thread has terminated
Created with the detach attribute. When an
When this condition is detected. This situation
Command checks if a thread has terminated
Exception or a cancel without joining or
Rwlock-id is provided, the command displays
Provided, the command displays extended
Is provided, the command displays extended
Condvar-id is provided, the command displays
For 64-bit PA applications
Thread Debugging in Batch Mode
Pre-requisites for Batch mode of Thread Debugging
For 64 bit IPF applications, set
For 64-bit PA applications, set
Set the environment variable Batchrtc to on as
And/Or
Opt/langtools/lib/hpux64/librtc.so
Thread Debugging in +check Mode
Where Pid is the process id
Limitations in Batch mode of thread debugging
Where pid is the process identifier
Issue
Debugging MPI Programs
Debugger response to a program call to fork or vfork is ask
Ask mode for set follow-fork-mode
Serial mode for set follow-fork-mode
Support for showing unwind info
Printing CFM and PFS registers
Command to Search for a Pattern in the Memory Address Space
Within double quotes. This parameter is mandatory
Parameter is mandatory when end-addressis not
Specifies the length of the memory address range. This
String value. The character pattern must be enclosed
Example 14-1 Sample Output for the find command
Specifies the pattern expr1
Using the /max-countparameter
Using the /size-charparameter
Str0 Specifies the starting address
Generating core files with packcore /unpackcore/getcore
Debugging Core Files
Support for the info target Command
Enhancements to the dumpcore command
Support for the dumpcore command
When starting from the HP WDB command line
When starting from the shell prompt
Sample Output
When starting from shell prompt
Support for display of run time type information
Info rtti address
Info exec-path summary
Info global-exec-path summary
Exec-path updownpathindex aliased to ep
Example Illustrating Execution Path Recovery
Sample Program
Sample Debugging Session
Command to Unwind Beyond 10000 Frames
Invoking GDB Before a Program Aborts
Aborting a Command Line Call
Hardware watchpoints
Instruction Level Stepping
Enhanced support for watchpoints and breakpoints
Deferred watchpoints
Rdp
Support for procedural breakpoints
Support for template breakpoints
Rbp
Debugging support for shared libraries
Using shared library as main program
Setting Deferred Breakpoints in Shared Library
Using catch load
Privately mapping shared libraries
Opt/langtools/bin/pxdb -s on executable-name
Selectively Mapping Shared Libraries As Private
Printing Decimal Floating point data types
Setting breakpoints in shared library
Enhancement to the info shared Command
Debugging support for Decimal Floating Point data type
Evaluating Decimal Floating Point data types
Following are sample commands to print NaT registers
Printing NaT Registers
Handling Decimal Floating Point Data types
Printing type of Decimal Floating Point variable
Assignment of Decimal floating point value to variable
Arithmetic Operations
Comparison Operations
This prints the binary floating point value as double
Additional Support for binary floating point data type
Support for Binary Floating Point constants f, l
This prints the binary floating point value as oat
Java Stack Unwind Features
Language support
Enhanced Java Debugging Support
Gdb help java
Gdb Subcommands for Java VM Debugging
Stack frame
Frame command of GDB has been enhanced to interpret a Java
Java and native stack frames
Info frame
Java corefile debugging support
Java attach mode debugging support
Syntax
Enhanced support for C++ templates
Support for fpreg data type on IPF
Support for Complex variables in HP C
Support for debugging namespaces
Command for evaluating the address of an expression
Viewing Wide Character Strings
This is equivalent to executing
Support for dumping array in an Ascii file
Support for output logging
Support for debugging typedefs
Support for steplast command for C and C++
Support for Fortran array slices
Displaying enumerators
Getting information from a non-debug executable
Debugging optimized code
Break Call Clear Disassem List
Break Call Cond Jump Return Print Set var Watch Whatis
HP-UX Configuration-Specific Information
Debugging Optimized Code at Various Optimization Levels
14.29.1.1 +O0 and +O1
14.29.1.2 +O2/+O3/+O4/-ipo
Following limitations apply when debugging optimized code
Debugging with Aries
+O2 or -O
Limitations of GDB Support under Aries
Debugging the application using GDB under Aries
Attaching GDB to an already running emulated process
Detecting memory leaks using GDB under Aries
Starting and stopping Visual Interface for WDB
Visual Interface for WDB
Visual Interface for WDB GUI display
Navigating the Visual Interface for WDB display
Specifying foreground and background colors
Using the X-window graphical interface
Using the TUI mode
Changing the size of the source or debugger pane
For dterm, use the following
Loading source files
Using commands to browse through source files
Editing the command line and command-line history
Saving the contents of a debugging session to a file
Stop in/at dbx commands
Support for XDB commands
GNU GDB Logging Commands
Support for command line calls in a stripped executable
For 32-bit applications
Execute the chatr -B immediate executable command
Printing of locals and globals in a stripped module
Command line calls to non-stripped library
Support for debugging stripped binaries
For 64-bit applications
Displaying the current block scope information
Linux support
Syntax
242
Main
Invoke the debugger using a command like the following
HP-UX Terminal User Interface
Starting the TUI
Screen Layouts
Automatically running a program at startup
Pane looks like this
Disassembly pane
Disassembly pane appears when you issue the command
Source pane
Source/Disassembly pane
Disassembly/Register pane
Source/Disassembly pane appears when you issue the command
Source/Register pane
Source/Register pane appears when you issue the command
Changing pane focus
Use the commands
Toggle split-screen mode
Cycling through the panes
Fs regs Foc next
Changing the register display
Scrolling panes
Changing the pane size
Refreshing and updating the window
XDB to WDB Transition Guide
By-function lists of XDB commands and HP WDB equivalents
Window mode commands
Invocation commands
Window mode commands
Invocation commands
File viewing commands
File viewing commands
Data Viewing and modification commands
Source directory mapping commands
Ll string Lm string
Data viewing and modification commands
Stack viewing commands
Stack viewing commands
Job control commands
Status-viewing command
Job control commands
Status viewing commands
Overall breakpoint commands
Auxiliary breakpoint commands
Overall breakpoint commands
Breakpoint creation commands
Auxillary breakpoint commands
10 Breakpoint creation commands
11 Overall breakpoint commands
Breakpoint status commands
Bp bpt bpx dp Dpt Dpx
All-procedures breakpoint commands
Global breakpoint commands
12 Global breakpoint commands
Assertion control commands
Record and playback commands
Macro facility commands
14 Signal control commands
Signal control commands
Miscellaneous commands
13 Macro facility commands
Format of the print command is different in XDB and GDB
16 Data format commands
XDB data formats and HP WDB equivalents
Decimal integer
17 Macro facility commands
XDB location syntax and HP WDB equivalents
XDB special language operators and HP WDB equivalents
XDB special variables and HP WDB equivalents
18 Special language operators
19 Special variables
20 Variable Identifiers
Alphabetical lists of XDB commands and HP WDB equivalents
XDB variable identifiers and HP WDB equivalents
16.8.1 a
22 B
16.8.2 B
23 C through D
Through D
25 L
Through K
16.8.5 L
24 F through K
26 M through P
Through P
28 T
Through S
16.8.8 T
27 Q through S
29 U through Z
Through Z
30 Symbols
Symbols
Any string
Control-C # text
280
Controlling GDB
Setting the GDB Prompt
Setting Command Editing Options in GDB
Setting Command History Feature in GDB
Expansion or through the history command
Control the settings
To fname. This is the file where GDB reads an
Exits. You can access this list through history
Supported Number Formats
Setting the GDB Screen Size
Optional warnings and messages
Optional messages about internal happenings
Set confirm on
Show confirm Displays state of confirmation requests
Object debugging info
Show debug varobj
User-defined commands
Canned Sequences of Commands
User-defined command hooks
To add source directories or
Command files
Commands for controlled output
Output formats
Expressions
292
Using GDB under gnu Emacs
GDB up command
Calls, like the GDB next command. Then update the display
Execute to next instruction, using the GDB nexti command
Update display window accordingly
295
296
What is an annotation?
GDB Annotations
Server prefix
Values
When printing a structure, GDB annotates it as follows
When printing an array, GDB annotates it as follows
Frames
Frame annotation begins with
Then comes
Annotation for GDB input
Displays
Information on breakpoints
Errors
Running the program
Invalidation notices
Displaying source
Target-invalid
Annotations We Might Want in the Future
306
GDB/MI Interface
21.1 GDB/MI Command Syntax
Done running connected error exit
21.1.2 GDB/MI Output syntax
Pragmatics
Value Const tuple list String Tuple →
Here is an example to evaluate an expression
Here is what happens if you pass a bad command
21.2 GDB/MI compatibility with CLI
Simple examples of GDB/MI interaction
21.3.2 GDB/MI stream records
21.4 GDB/MI command description format
21.3 GDB/MI output records
21.3.1 GDB/MI result records
-break-after Command
21.5 GDB/MI breakpoint table commands
Corresponding GDB command is condition
-break-condition command
Corresponding GDB command is disable
-break-delete command
-break-disable command
Corresponding GDB command is delete
-break-info Command
-break-enable command
Result
-break-insert command
-break-list command
-break-watch command
Corresponding GDB commands are watch, awatch, and rwatch
Setting a watchpoint on a variable in the main function
Exec-continue running gdb
21.6 GDB/MI Data manipulation
-data-disassemble command
There is no direct mapping from this command to the CLI
Disassemble from the current value of $pc to $pc +
Disassemble 3 instructions from the start of main
-data-evaluate-expression command
On a PPC MBX board
-data-list-changed-registers Command
-data-list-register-names command
Display a list of the registers that have changed
-data-list-register-values command
-data-read-memory command
Space should be quoted using the C convention
To be read. Complex expressions containing embedded white
Word-format Word-sizenr-rowsnr-cols aschar
-display-disable Command
-display-delete command
-environment-cd command
-display-enable command
-display-insert Command
-display-list command
-environment-path command
-environment-directory command
Show the current working directory
-environment-pwd command
Corresponding GDB command is pwd
21.7 GDB/MI program control
-exec-abort command
-exec-arguments command
-exec-continue command
Corresponding GDB command is interrupt
-exec-finish command
-exec-interrupt command
Corresponding GDB command is finish
Corresponding GDB command is nexti
-exec-nextcommand Synopsis
-exec-next-instruction command
Corresponding GDB command is next
Corresponding GDB command is run
-exec-return command
-exec-runcommand Synopsis
Corresponding GDB command is return
Example -exec-stepCommand Synopsis
-exec-show-arguments command
Regular stepping
-exec-step-instruction command
-exec-until command
Corresponding GDB command is stepi
Corresponding GDB command is file
-file-exec-and-symbols command
-file-exec-file command
Corresponding GDB command is until
-file-list-exec-sections command
-file-list-exec-source-files command
-file-list-shared-libraries command
-gdb-exitcommand Synopsis
Miscellaneous GDB commands in GDB/MI
-file-list-symbol-files command
-file-symbol-file command
-gdb-setcommand Synopsis
-gdb-showcommand Synopsis
-gdb-version command
21.9 GDB/MI Stack Manipulation Commands
-stack-info-frame command
-stack-info-depth command
For a stack with frame levels 0 through
-stack-list-arguments command Synopsis
-stack-list-frames command
Show a single frame
Corresponding GDB commands are backtrace and where
Full stack backtrace
Show frames between lowframe and highframe
-stack-list-locals command
-stack-select-frame command
Info locals in GDB, gdbgetlocals in gdbtk
-symbol-info-function command
21.10 GDB/MI Symbol query commands
-symbol-info-address command
-symbol-info-file command
-symbol-list-types command
-symbol-info-line command
-symbol-info-symbol command
-symbol-list-functions command
-symbol-list-variables command
-symbol-locate command
-symbol-type command
-target-detach command
21.11 GDB/MI Target Manipulation Commands
-target-attach command
-target-compare-sections command
At the end, a summary is printed
-target-download command
Corresponding GDB command is load
Name of the section
-target-exec-status command
-target-list-available-targets command
-target-list-current-targets command
-target-list-parameters command
-thread-list-all-threads command
21.12 GDB/MI thread commands
-target-select command
-thread-info command
-thread-select command
-thread-list-ids command
21.13 GDB/MI tracepoint commands
Tracepoint commands are not yet implemented
21.14 GDB/MI variable objects
-var-create command
GDB/MI Operations
Description and use of operations on variable objects
-var-info-num-children command
-var-delete command
-var-set-format command
-var-show-format command
-var-show-attributes command
-var-list-children command
-var-info-type command
-var-info-expression command
-var-update command
-var-assign command
360
How to report bugs
Reporting Bugs in GDB
Have you found a bug?
Reporting Bugs in GDB
How to report bugs
364
Installing GDB
Compiling GDB in another directory
Gdb-gdb-199991101/mmalloc
Package
Specifying names for hosts and targets
Srcdir= dirname
Configure options
Separate directories. configure writes configuration
To use the source in the directory dirname. configure
All available targets
Target=target