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Debugging with GDB

21.1 TUI overview

The TUI has two display modes that can be switched while GDB runs:

• A curses (or TUI) mode in which it displays several text windows on the terminal.

• A standard mode which corresponds to the GDB configured without the TUI.

In the TUI mode, GDB can display several text window on the terminal:

command

This window is the GDB command window with the GDB prompt and the GDB outputs. The GDB input is still managed using readline but through the TUI. The command window is always visible.

source

The source window shows the source file of the program. The current line as well as active breakpoints are displayed in this window.

assembly

The assembly window shows the disassembly output of the program.

register

This window shows the processor registers. It detects when a register is changed and when this is the case, registers that have changed are highlighted.

The source and assembly windows show the current program position by highlighting the current line and marking them with the `>' marker. Breakpoints are also indicated with two markers. A first one indicates the breakpoint type:

B

Breakpoint which was hit at least once.

b

Breakpoint which was never hit.

H

Hardware breakpoint which was hit at least once.

h

Hardware breakpoint which was never hit.

The second marker indicates whether the breakpoint is enabled or not:

+

Breakpoint is enabled.

-

Breakpoint is disabled.

The source, assembly and register windows are attached to the thread and the frame position. They are updated when the current thread changes, when the frame changes or when the program counter changes. These three windows are arranged by the TUI according to several layouts. The layout defines which of these three windows are visible. The following layouts are available:

• source

• assembly

• source and assembly

• source and registers

• assembly and registers

On top of the command window a status line gives various information concerning the current process begin debugged. The status line is updated when the information it shows changes. The following fields are displayed:

target

Indicates the current gdb target (see section Specifying a Debugging Target).

process

Gives information about the current process or thread number. When no process is being debugged, this field is set to No process.

function

Gives the current function name for the selected frame. The name is demangled if demangling is turned on (see section 8.7 Print settings). When there is no symbol corresponding to the current program counter the string ?? is displayed.

line

Indicates the current line number for the selected frame. When the current line number is not known the string ?? is displayed.

pc

Indicates the current program counter address.