19.2 Commands for Managing Targets

target type parameters

Connects the GDB host environment to a target machine or process. A target is typically a protocol for talking to debugging facilities. You use the argument type to specify the type or protocol of the target machine.

Further parameters are interpreted by the target protocol, but typically include things like device names or host names to connect with, process numbers, and baud rates.

The target command does not repeat if you press RET again after executing the command.

help target

Displays the names of all targets available. To display targets currently selected, use either info target or info files (see Commands to Specify Files).

help target name

Describe a particular target, including any parameters necessary to select it.

set gnutarget args

GDB uses its own library BFD to read your files. GDB knows whether it is reading an executable, a core, or a .o file; however, you can specify the file format with the set gnutarget command. Unlike most target commands, with gnutarget the target refers to a program, not a machine.

Warning: To specify a file format with set gnutarget, you must know the actual BFD name.

See Commands to Specify Files.

show gnutarget

Use the show gnutarget command to display what file format gnutarget is set to read. If you have not set gnutarget, GDB will determine the file format for each file automatically, and show gnutarget displays ‘The current BFD target is "auto"’.

Here are some common targets (available, or not, depending on the GDB configuration):

target exec program

An executable file. ‘target exec program’ is the same as ‘exec-file program’.

target core filename

A core dump file. ‘target core filename’ is the same as ‘core-file filename’.

target remote medium

A remote system connected to GDB via a serial line or network connection. This command tells GDB to use its own remote protocol over medium for debugging. See Remote Debugging.

For example, if you have a board connected to /dev/ttya on the machine running GDB, you could say:

target remote /dev/ttya

target remote supports the load command. This is only useful if you have some other way of getting the stub to the target system, and you can put it somewhere in memory where it won’t get clobbered by the download.

target sim [simargs] …

Builtin CPU simulator. GDB includes simulators for most architectures. In general,

        target sim
        load
        run

works; however, you cannot assume that a specific memory map, device drivers, or even basic I/O is available, although some simulators do provide these. For info about any processor-specific simulator details, see the appropriate section in Embedded Processors.

target native

Setup for local/native process debugging. Useful to make the run command spawn native processes (likewise attach, etc.) even when set auto-connect-native-target is off (see set auto-connect-native-target).

Different targets are available on different configurations of GDB; your configuration may have more or fewer targets.

Many remote targets require you to download the executable’s code once you’ve successfully established a connection. You may wish to control various aspects of this process.

set hash

This command controls whether a hash mark ‘#’ is displayed while downloading a file to the remote monitor. If on, a hash mark is displayed after each S-record is successfully downloaded to the monitor.

show hash

Show the current status of displaying the hash mark.

set debug monitor

Enable or disable display of communications messages between GDB and the remote monitor.

show debug monitor

Show the current status of displaying communications between GDB and the remote monitor.

load filename offset

Depending on what remote debugging facilities are configured into GDB, the load command may be available. Where it exists, it is meant to make filename (an executable) available for debugging on the remote system—by downloading, or dynamic linking, for example. load also records the filename symbol table in GDB, like the add-symbol-file command.

If your GDB does not have a load command, attempting to execute it gets the error message “You can't do that when your target is …”

The file is loaded at whatever address is specified in the executable. For some object file formats, you can specify the load address when you link the program; for other formats, like a.out, the object file format specifies a fixed address.

It is also possible to tell GDB to load the executable file at a specific offset described by the optional argument offset. When offset is provided, filename must also be provided.

Depending on the remote side capabilities, GDB may be able to load programs into flash memory.

load does not repeat if you press RET again after using it.

flash-erase

Erases all known flash memory regions on the target.