Debugging with GDB (February 2008)
Table Of Contents
- Summary of GDB
- A Sample GDB Session
- Getting In and Out of GDB
- GDB Commands
- Running Programs Under GDB
- Stopping and Continuing
- Examining the Stack
- Examining Source Files
- Examining Data
- Using GDB with Different Languages
- Examining the Symbol Table
- Altering Execution
- GDB Files
- Specifying a Debugging Target
- HP-UX Configuration-Specific Information
- Summary of HP Enhancements to GDB
- HP-UX dependencies
- Supported Platforms and Modes
- HP-UX targets
- Support for Alternate root
- Specifying object file directories
- Fix and continue debugging
- Inline Support
- Debugging Macros
- Debugging Memory Problems
- When to suspect a memory leak
- Memory debugging restrictions
- Memory Debugging Methodologies
- Debugging Memory in Interactive Mode
- Debugging Memory in Batch Mode
- Debugging Memory Interactively After Attaching to a Running Process
- Configuring memory debugging settings
- Scenarios in memory debugging
- Stop when freeing unallocated or deallocated blocks
- Stop when freeing a block if bad writes occurred outside block boundary
- Stop when a specified block address is allocated or deallocated
- Scramble previous memory contents at malloc/free calls
- Detect dangling pointers and dangling blocks
- Detect in-block corruption of freed blocks
- Specify the amount of guard bytes for every block of allocated memory
- Comparison of Memory Debugging Commands in Interactive Mode and Batch Mode
- Heap Profiling
- Memory Checking Analysis for User Defined Memory Management Routines
- Commands to track the change in data segment value
- Thread Debugging Support
- Debugging MPI Programs
- Debugging multiple processes ( programs with fork and vfork calls)
- Debugging Core Files
- Printing the Execution Path Entries for the Current Frame or Thread
- Invoking GDB Before a Program Aborts
- Aborting a Command Line Call
- Instruction Level Stepping
- Enhanced support for watchpoints and breakpoints
- Debugging support for shared libraries
- Language support
- Enhanced Java Debugging Support
- Commands for Examining Java Virtual Machine(JVM) internals
- Support for stack traces in Java, C, and C++ programs
- Support for 64-bit Java, C, aC++ stack unwinding
- 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
- Support for output logging
- Getting information from a non-debug executable
- Debugging optimized code
- Visual Interface for WDB
- Starting and stopping Visual Interface for WDB
- 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
- Using commands to browse through source files
- Loading source files
- Editing source files
- Editing the command line and command-line history
- Saving the contents of a debugging session to a file
- Support for ddd
- Support for XDB commands
- GNU GDB Logging Commands
- Support for command line calls in a stripped executable
- Displaying the current block scope information
- Linux support
- The HP-UX Terminal User Interface
- XDB to WDB Transition Guide
- By-function lists of XDB commands and HP WDB equivalents
- Overall breakpoint commands
- XDB data formats and HP WDB equivalents
- XDB location syntax and HP WDB equivalents
- XDB special language operators and HP WDB equivalents
- XDB special variables and HP WDB equivalents
- XDB variable identifiers and HP WDB equivalents
- Alphabetical lists of XDB commands and HP WDB equivalents
- Controlling GDB
- Canned Sequences of Commands
- Using GDB under gnu Emacs
- GDB Annotations
- The gdb/mi Interface
- Function and purpose
- Notation and terminology
- gdb/mi Command Syntax
- gdb/mi compatibility with CLI
- gdb/mi output records
- gdb/mi command description format
- gdb/mi breakpoint table commands
- gdb/mi Data manipulation
- gdb/mi program control
- Miscellaneous GDB commands in gdb/mi
- gdb/mi Stack Manipulation Commands
- gdb/mi Symbol query commands
- gdb/mi Target Manipulation Commands
- gdb/mi thread commands
- gdb/mi tracepoint commands
- gdb/mi variable objects
- Reporting Bugs in GDB
- Installing GDB
- Index
Chapter 14: HP-UX Configuration-Specific Information 175
(gdb) symbol-file main.sl
Load new symbol table from "main.sl"? (y or n) y
Reading symbols from main.sl
done.
Things don’t appear to work.
This command is not the correct thing to do. This command assumes that main.sl is
loaded at its link time address. This is not not true for shared libraries.
Do not use symbol-file with shared libraries.
Instead, what you should do is to use the deferred breakpoint feature to set breakpoints
on any functions necessary before the program starts running.
(gdb) b main
Breakpoint 1 (deferred) at "main" ("main" was not found).
Breakpoint deferred until a shared library containing "main" is loaded.
(gdb) r
Once the program has started running, it will hit the breakpoint. In addition, the de-
bugger will then already know about the sources for main, since it gets this information
when the shared library is loaded.
14.20.2 Setting Deferred Breakpoints in Shared Library
On HP-UX, GDB automatically loads symbol definitions from shared libraries when
you use the run command, or when you examine a core file. (Before you issue the run
command, GDB does not understand references to a function in a shared library—
unless you are debugging a core file.)
When you specify a breakpoint using a name that GDB does not recognize, the debug-
ger warns you with a message that it is setting a deferred breakpoint on the name you
specified. If any shared library is loaded with a matching name, then GDB sets the
breakpoint.
For example, if you type:
‘break foo’
the debugger does not know whether foo is a misspelled name or whether it is the name
of a routine that has not yet been loaded from a shared library. The debugger displays
a warning message that it is setting a deferred breakpoint on foo. If any shared library
is loaded that contains a foo, then GDB sets the breakpoint.
If this is not what you want (for example, if the name was mistyped), then you can
delete the breakpoint.
14.20.3 Using catch load
The ‘catch load <libname >’ command causes the debugger to stop when the partic-
ular library is loaded. This gives you a chance to set breakpoints before routines are
executed.