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Selecting the target system

You can specify three aspects of the target system to the GNU binary file utilities, each in several ways:

In the following summaries, the lists of ways to specify values are in order of decreasing precedence. The ways listed first override those listed later.

The commands to list valid values only list the values for which the programs you are running were configured. If they were configured with `--with-targets=all', the commands list most of the available values, but a few are left out; not all targets can be configured in at once because some of them can only be configured native (on hosts with the same type as the target system).

Target Selection

A target is an object file format. A given target may be supported for multiple architectures (see section Architecture selection). A target selection may also have variations for different operating systems or architectures.

The command to list valid target values is `objdump -i' (the first column of output contains the relevant information).

Some sample values are: `a.out-hp300bsd', `ecoff-littlemips', `a.out-sunos-big'.

objdump Target

Ways to specify:

  1. command line option: `-b' or `--target'

  2. environment variable GNUTARGET

  3. deduced from the input file

objcopy and strip Input Target

Ways to specify:

  1. command line options: `-I' or `--input-target', or `-F' or `--target'

  2. environment variable GNUTARGET

  3. deduced from the input file

objcopy and strip Output Target

Ways to specify:

  1. command line options: `-O' or `--output-target', or `-F' or `--target'

  2. the input target (see "objcopy and strip Input Target" above)

  3. environment variable GNUTARGET

  4. deduced from the input file

nm, size, and strings Target

Ways to specify:

  1. command line option: `--target'

  2. environment variable GNUTARGET

  3. deduced from the input file

Linker Input Target

Ways to specify:

  1. command line option: `-b' or `--format' (see section `Options' in Using LD)

  2. script command TARGET (see section `Option Commands' in Using LD)

  3. environment variable GNUTARGET (see section `Environment' in Using LD)

  4. the default target of the selected linker emulation (see section Linker emulation selection)

Linker Output Target

Ways to specify:

  1. command line option: `-oformat' (see section `Options' in Using LD)

  2. script command OUTPUT_FORMAT (see section `Option Commands' in Using LD)

  3. the linker input target (see "Linker Input Target" above)

Architecture selection

An architecture is a type of CPU on which an object file is to run. Its name may contain a colon, separating the name of the processor family from the name of the particular CPU.

The command to list valid architecture values is `objdump -i' (the second column contains the relevant information).

Sample values: `m68k:68020', `mips:3000', `sparc'.

objdump Architecture

Ways to specify:

  1. command line option: `-m' or `--architecture'

  2. deduced from the input file

objcopy, nm, size, strings Architecture

Ways to specify:

  1. deduced from the input file

Linker Input Architecture

Ways to specify:

  1. deduced from the input file

Linker Output Architecture

Ways to specify:

  1. script command OUTPUT_ARCH (see section `Option Commands' in Using LD)

  2. the default architecture from the linker output target (see section Target Selection)

Linker emulation selection

A linker emulation is a "personality" of the linker, which gives the linker default values for the other aspects of the target system. In particular, it consists of

The command to list valid linker emulation values is `ld -V'.

Sample values: `hp300bsd', `mipslit', `sun4'.

Ways to specify:

  1. command line option: `-m' (see section `Options' in Using LD)

  2. environment variable LDEMULATION

  3. compiled-in DEFAULT_EMULATION from `Makefile', which comes from EMUL in `config/target.mt'

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