Debugging with GDB Manual (5900-1473; WDB 6.2; January 2011)

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Table Of Contents

Debugging with GDB Manual
Contents
Summary of GDB
- Free Software
- Contributors to GDB
1 A Sample GDB Session
- 1.1 Loading the Executable
- 1.2 Setting Display width
- 1.3 Setting Breakpoints
- 1.4 Running the executable under GDB
- 1.5 Stepping to the next line in the source program
- 1.6 Stepping into a subroutine
- 1.7 Examining the Stack
- 1.8 Printing Variable Values
- 1.9 Listing Source Code
- 1.10 Setting Variable Values During a Session
2 Getting In and Out of GDB
- 2.1 Invoking GDB
- 2.2 Quitting GDB
- 2.3 Shell commands
3 GDB Commands
- 3.1 Command syntax
- 3.2 Command completion
- 3.3 Getting help
4 Running Programs Under GDB
- 4.1 Compiling for debugging
- 4.2 Starting your program
- 4.3 Arguments To Your Program
- 4.4 Program Environment
- 4.5 Working directory
- 4.6 Program Input and Output
- 4.7 Debugging a Running Process
- 4.8 Killing the child process
- 4.9 Debugging programs with multiple threads
- 4.10 Debugging programs with multiple processes
5 Stopping and Continuing
- 5.1 Breakpoints
- 5.2 Continuing and stepping
- 5.3 Signals
- 5.4 Stopping and starting multi-thread programs
6 Examining the Stack
- 6.1 Stack frames
- 6.2 Stacks Without frames
- 6.3 Commands for Examining the Stack
- 6.4 Backtraces
- 6.5 Selecting a frame
- 6.6 Information about a frame
7 Examining Source Files
- 7.1 Printing source lines
- 7.2 Searching source files
- 7.3 Specifying source directories
- 7.4 Source and machine code
8 Examining Data
- 8.1 Expressions
- 8.2 Program variables
- 8.3 Artificial arrays
- 8.4 Output formats
- 8.5 Examining memory
- 8.6 Automatic display
- 8.7 Print settings
- 8.8 Value history
- 8.9 Convenience variables
- 8.10 Registers
- 8.11 Printing Floating Point Values
- 8.12 Floating point hardware
- 8.13 Functions
9 Using GDB with Different Languages
- 9.1 Switching between source languages
- 9.2 Displaying the language
- 9.3 Type and range checking
  - 9.3.1 An overview of type checking
  - 9.3.2 An overview of range checking
- 9.4 Supported languages
  - 9.4.1 C and C++
  - 9.4.2 Fortran
10 Examining the Symbol Table
11 Altering Execution
- 11.1 Assignment to variables
- 11.2 Continuing at a different address
- 11.3 Giving your program a signal
- 11.4 Returning from a function
- 11.5 Calling program functions
- 11.6 Patching programs
12 GDB Files
- 12.1 Commands to specify files
- 12.2 Specifying shared library locations
- 12.3 Errors reading symbol files
13 Specifying a Debugging Target
- 13.1 Active targets
- 13.2 Commands for managing targets
- 13.3 Choosing target byte order
14 HP-UX Configuration-Specific Information
- 14.1 Summary of HP Enhancements to GDB
- 14.2 HP-UX dependencies
  - 14.2.1 Linker Dependencies
  - 14.2.2 Dependent Standard Library Routines for Run Time Checking
- 14.3 Supported Platforms and Modes
- 14.4 HP-UX targets
- 14.5 Support for Alternate root
- 14.6 Specifying object file directories
- 14.7 Fix and continue debugging
  - 14.7.1 Fix and Continue compiler dependencies
  - 14.7.2 Fix and Continue restrictions
  - 14.7.3 Using Fix and Continue
  - 14.7.4 Example Fix and Continue session
- 14.8 Inline Support
  - 14.8.1 Inline Debugging in HP 9000 Systems
  - 14.8.2 Inline Debugging in Integrity Systems
    - 14.8.2.1 Debugging Inline Functions in Integrity Systems
- 14.9 Debugging Macros
  - 14.9.1 Viewing and Evaluating Macro Definitions
    - 14.9.1.1 Compiler Options to Enable Macro Debugging
  - 14.9.2 Examples for Macro Debugging
- 14.10 Debugging Memory Problems
  - 14.10.1 When to suspect a memory leak
  - 14.10.2 Memory debugging restrictions
  - 14.10.3 Memory Debugging Methodologies
  - 14.10.4 Debugging Memory in Interactive Mode
    - 14.10.4.1 Commands for interactive memory debugging
    - 14.10.4.2 Example for interactive debugging session
  - 14.10.5 Debugging Memory in Batch Mode
  - 14.10.6 Debugging Memory Interactively After Attaching to a Running Process
  - 14.10.7 Open-files reporting
  - 14.10.8 Configuring memory debugging settings
  - 14.10.9 Scenarios in memory debugging
  - 14.10.10 Comparison of Memory Debugging Commands in Interactive Mode and Batch Mode
  - 14.10.11 Heap Profiling
  - 14.10.12 Memory Checking Analysis for User Defined Memory Management Routines
  - 14.10.13 Commands to track the change in data segment value
  - 14.10.14 Support for Memory Debugging Feature on Applications Using libmallocng Library for Heap Allocation Management
- 14.11 Thread Debugging Support
  - 14.11.1 Support for Enabling and Disabling Specific Threads
  - 14.11.2 Backtrace Support for Thread Debugging
  - 14.11.3 Advanced Thread Debugging Support
  - 14.11.4 Debugging Threads Interactively After Attaching to a Process
  - 14.11.5 Thread Debugging in Batch Mode
    - 14.11.5.1 Pre-requisites for Batch mode of Thread Debugging
    - 14.11.5.2 Limitations in Batch mode of thread debugging
  - 14.11.6 Thread Debugging in +check Mode
  - 14.11.7 Known issues with Thread Debugging for Interactive and Batch mode
- 14.12 Debugging MPI Programs
- 14.13 Debugging multiple processes (programs with fork and vfork calls)
  - 14.13.1 Ask mode for set follow-fork-mode
  - 14.13.2 Serial mode for set follow-fork-mode
  - 14.13.3 Support for showing unwind info
- 14.14 Command to Search for a Pattern in the Memory Address Space
- 14.15 Debugging Core Files
  - 14.15.1 Generating core files with packcore /unpackcore/getcore
  - 14.15.2 Support for the info target Command
  - 14.15.3 Support for the dumpcore command
    - 14.15.3.1 Enhancements to the dumpcore command
  - 14.15.4 Support for display of run time type information
  - 14.15.5 Support for Core File Debugging of MITR Applications
  - 14.15.6 Support for mmapfile command
- 14.16 Debugging with debug information available in the side debug file
- 14.17 Printing the Execution Path Entries for the Current Frame or Thread
  - 14.17.1 Compiler Dependencies for Printing the Execution Path Entries
  - 14.17.2 Example Illustrating Execution Path Recovery
- 14.18 Command to Unwind Beyond 10000 Frames
- 14.19 Invoking GDB Before a Program Aborts
- 14.20 Aborting a Command Line Call
- 14.21 Instruction Level Stepping
- 14.22 Enhanced support for watchpoints and breakpoints
  - 14.22.1 Deferred watchpoints
  - 14.22.2 Hardware watchpoints
  - 14.22.3 Hardware breakpoints
    - 14.22.3.1 Setting breakpoints in unstripped shared library
  - 14.22.4 Support for procedural breakpoints
  - 14.22.5 Support for template breakpoints
- 14.23 Debugging support for shared libraries
  - 14.23.1 Using shared library as main program
  - 14.23.2 Setting Deferred Breakpoints in Shared Library
  - 14.23.3 Using catch load
  - 14.23.4 Privately mapping shared libraries
  - 14.23.5 Selectively Mapping Shared Libraries As Private
  - 14.23.6 Setting breakpoints in shared library
  - 14.23.7 Enhancement to the info shared Command
- 14.24 Debugging support for Decimal Floating Point data type
  - 14.24.1 Printing Decimal Floating point data types
    - 14.24.1.1 Printing Decimal floating point constant
    - 14.24.1.2 Printing Decimal floating point variable
  - 14.24.2 Handling Decimal Floating Point Data types
  - 14.24.3 Evaluating Decimal Floating Point data types
    - 14.24.3.1 Printing type of Decimal Floating Point variable
- 14.25 Additional Support for binary floating point data type
  - 14.25.1 Support for Binary Floating Point constants f, l
  - 14.25.2 Support Binary Floating Point variables with format specifier
- 14.26 Language support
  - 14.26.1 Enhanced Java Debugging Support
  - 14.26.2 Enhanced support for C++ templates
  - 14.26.3 Support for _ _fpreg data type on IPF
  - 14.26.4 Support for _Complex variables in HP C
  - 14.26.5 Support for debugging namespaces
  - 14.26.6 Command for evaluating the address of an expression
- 14.27 Viewing Wide Character Strings
- 14.28 Support for output logging
  - 14.28.1 Support for dumping array in an ASCII file
  - 14.28.2 Support for Fortran array slices
  - 14.28.3 Displaying enumerators
  - 14.28.4 Support for debugging typedefs
  - 14.28.5 Support for steplast command for C and C++
- 14.29 Getting information from a non-debug executable
- 14.30 Debugging optimized code
  - 14.30.1 Debugging Optimized Code at Various Optimization Levels
    - 14.30.1.1 +O0 and +O1
    - 14.30.1.2 +O2/+O3/+O4/-ipo
- 14.31 Debugging with ARIES
  - 14.31.1 Debugging the application using GDB under ARIES
    - 14.31.1.1 Limitations of GDB Support under ARIES
  - 14.31.2 Attaching GDB to an already running emulated process
  - 14.31.3 Detecting memory leaks using GDB under ARIES
- 14.32 Visual Interface for HP WDB
  - 14.32.1 Starting and stopping Visual Interface for HP WDB
  - 14.32.2 Navigating the Visual Interface for HP WDB display
  - 14.32.3 Specifying foreground and background colors
  - 14.32.4 Using the X-window graphical interface
  - 14.32.5 Using the TUI mode
  - 14.32.6 Changing the size of the source or debugger pane
  - 14.32.7 Using commands to browse through source files
  - 14.32.8 Loading source files
  - 14.32.9 Editing source files
  - 14.32.10 Editing the command line and command-line history
  - 14.32.11 Saving the contents of a debugging session to a file
- 14.33 Support for ddd
- 14.34 Support for XDB commands
  - 14.34.1 stop in/at dbx commands
- 14.35 GDB Logging Commands
- 14.36 Support for command line calls in a stripped executable
  - 14.36.1 Support for command line calls in a stripped executable on PA-RISC systems
  - 14.36.2 Additional support for command line calls in a stripped executable
    - 14.36.2.1 For 32-bit applications:
    - 14.36.2.2 For 64-bit applications
  - 14.36.3 Support for debugging stripped binaries
- 14.37 Displaying the current block scope information
- 14.38 Linux support
- 14.39 Source level debugging
- 14.40 Support for using old DW-VIRTUALITY values
- 14.41 Additional support for examining registers
  - 14.41.1 Printing or changing the values of CFM and PFS registers
  - 14.41.2 Printing and setting NaT registers
15 The HP-UX Terminal User Interface
- 15.1 Starting the TUI
- 15.2 Automatically running a program at startup
- 15.3 Screen Layouts
- 15.4 Cycling through the panes
- 15.5 Changing pane focus
- 15.6 Scrolling panes
- 15.7 Changing the register display
- 15.8 Changing the pane size
- 15.9 Refreshing and updating the window
16 XDB to HP WDB Transition Guide
- 16.1 By-function lists of XDB commands and HP WDB equivalents
- 16.2 Overall breakpoint commands
- 16.3 XDB data formats and HP WDB equivalents
- 16.4 XDB location syntax and HP WDB equivalents
- 16.5 XDB special language operators and HP WDB equivalents
- 16.6 XDB special variables and HP WDB equivalents
- 16.7 XDB variable identifiers and HP WDB equivalents
- 16.8 Alphabetical lists of XDB commands and HP WDB equivalents
17 Controlling GDB
- 17.1 Setting the GDB Prompt
- 17.2 Setting Command Editing Options in GDB
- 17.3 Setting Command History Feature in GDB
- 17.4 Setting the GDB Screen Size
- 17.5 Supported Number Formats
- 17.6 Optional warnings and messages
- 17.7 Optional messages about internal happenings
- 17.8 Configuring the Current Application Binary Interface (ABI)
18 Canned Sequences of Commands
- 18.1 User-defined commands
- 18.2 User-defined command hooks
- 18.3 Command files
- 18.4 Commands for controlled output
19 Using GDB under gnu Emacs
20 GDB Annotations
- 20.1 What is an annotation?
- 20.2 The server prefix
- 20.3 Values
- 20.4 Frames
- 20.5 Displays
- 20.6 Annotation for GDB input
- 20.7 Errors
- 20.8 Information on breakpoints
- 20.9 Invalidation notices
- 20.10 Running the program
- 20.11 Displaying source
- 20.12 Annotations We Might Want in the Future
21 The GDB/MI Interface
- 21.1 GDB/MI Command Syntax
- 21.2 GDB/MI compatibility with CLI
- 21.3 GDB/MI output records
- 21.4 GDB/MI command description format
- 21.5 GDB/MI breakpoint table commands
- 21.6 GDB/MI Data manipulation
- 21.7 GDB/MI program control
- 21.8 Miscellaneous GDB commands in GDB/MI
- 21.9 GDB/MI Stack Manipulation Commands
- 21.10 GDB/MI Symbol query commands
- 21.11 GDB/MI Target Manipulation Commands
- 21.12 GDB/MI thread commands
- 21.13 GDB/MI tracepoint commands
- 21.14 GDB/MI variable objects
22 Reporting Bugs in GDB
- 22.1 Have you found a bug?
- 22.2 How to report bugs
A Installing GDB
- A.1 Compiling GDB in another directory
- A.2 Specifying names for hosts and targets
- A.3 configure options

'.cxx',

'.c++'

'.f',

'.F',

'.f90'

Fortran source file. GDB does not distinguish between Fortran 77 and Fortran

90 files.

'.s',

'.S'

Assembler source file. This actually behaves almost like C, but GDB does not

skip over function prologues when stepping.

In addition, you may set the language associated with a filename extension. See

“Displaying the language” (page 96).

9.1.2 Setting the working language

If you allow GDB to set the language automatically, expressions are interpreted the same

way in your debugging session and your program.

If you wish, you may set the language manually. To do this, issue the command 'set

language lang', where lang is the name of a language, such as c. For a list of the

supported languages, type 'set language'.

Setting the language manually prevents GDB from updating the working language

automatically. This can lead to confusion if you try to debug a program when the working

language is not the same as the source language, when an expression is acceptable to

both languages―but means different things. For instance, if the current source file was

written in C, and GDB was parsing Modula-2, a command such as:

print a = b + c

might not have the effect you intended. In C, this means to add b and c and place the

result in a. The result printed would be the value of a. In Modula-2, this means to compare

a to the result of b+c, yielding a BOOLEAN value.

9.1.3 Having GDB infer the source language

To have GDB set the working language automatically, use 'set language local' or

'set language auto'. GDB then infers the working language. That is, when your

program stops in a frame (usually by encountering a breakpoint), GDB sets the working

language to the language recorded for the function in that frame. If the language for a

frame is unknown (that is, if the function or block corresponding to the frame was defined

in a source file that does not have a recognized extension), the current working language

is not changed, and GDB issues a warning.

This may not seem necessary for most programs, which are written entirely in one source

language. However, program modules and libraries written in one source language can

be used by a main program written in a different source language. Using 'set

language auto' in this case frees you from having to set the working language

manually.

9.1 Switching between source languages 95