Arnold Robbins - GDB Pocket Reference: Debugging Quickly & Painlessly With GDB

Used for directory names, commands, program names, functions, variables, and options. All terms shown in constant width are typed literally. It is also used to show the contents of files or the output from commands.

Used in syntax and command summaries to show generic text; these should be replaced with user-supplied values.

Used in examples to show text that should be typed literally by the user.

Used to show generic arguments and options; these should be replaced with user-supplied values. Italic is also used to indicate URLs, macro package names, filenames, comments in examples, and the first mention of terms.

Used in some examples as the Bash, Bourne or Korn shell prompt.

Indicates the "manpage" for program in section N of the online manual. For example, echo (1) means the entry for the echo command.

Surround optional elements in a description of syntax. (The brackets themselves should never be typed.) Note that many commands show the argument [ files ]. If a filename is omitted, standard input (usually the keyboard) is assumed. End keyboard input with an end-of-file character.

indicates a "control character," typed by holding down the Control key and the x key for any key x .

Used in syntax descriptions to separate items for which only one alternative may be chosen at a time.

A debugger is a program that lets you run a second program, which we will call the debuggee. The debugger lets you examine and change the state of the debuggee, and control its execution. In particular, you can single-step the program, executing one statement or instruction at a time, in order to watch the program's behavior.

Debuggers come in two flavors: instruction-level debuggers, which work at the level of machine instructions, and source-level debuggers, which operate in terms of your program's source code and programming language. The latter are considerably easier to use, and usually can do machine-level debugging if necessary. GDB is a source-level debugger; it is probably the most widely applicable (portable to the largest number of architectures) of any current debugger.

GDB itself provides two user interfaces: the traditional command-line interface (CLI) and a text user interface (TUI). The latter is meant for regular terminals or terminal emulators, dividing the screen into separate "windows" for the display of source code, register values, and so on.

GDB provides support for debugging programs written in C, C++, Objective C, Java,[] and Fortran. It provides partial support for Modula-2 programs compiled with the GNU Modula-2 compiler and for Ada programs compiled with the GNU Ada Translator, GNAT. GDB provides some minimal support for debugging Pascal programs. The Chill language is no longer supported.

When working with C++ and Objective C, GDB provides name demangling. C++ and Objective C encode overloaded procedure names into a unique "mangled" name that represents the procedure's return type, argument types, and class membership. This ensures so-called type-safe linkage. There are different methods for name mangling, thus GDB allows you to select among a set of supported methods, besides just automatically demangling names in displays.

If your program is compiled with the GNU Compiler Collection (GCC), using the -g3 and -gdwarf-2 options, GDB understands references to C preprocessor macros. This is particularly helpful for code using macros to simplify complicated struct and union members. GDB itself also has partial support for expanding preprocessor macros, with more support planned.

GDB allows you to specify several different kinds of files when doing debugging:

There are different ways to stop your program:

The GDB documentation and command set often use the word breakpoint as a generic term to mean all three kinds of program stoppers. In particular, use the same commands to enable, disable, and remove all three.