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### 3.16 Specifying Target Machine and Compiler Version

The usual way to run GCC is to run the executable called `gcc`, or `<machine>-gcc` when cross-compiling, or `<machine>-gcc-<version>` to run a version other than the one that was installed last. Sometimes this is inconvenient, so GCC provides options that will switch to another cross-compiler or version.

`-b` machine
  The argument machine specifies the target machine for compilation.

  The value to use for machine is the same as was specified as the machine type when configuring GCC as a cross-compiler. For example, if a cross-compiler was configured with ‘`configure arm-elf`’, meaning to compile for an arm processor with elf binaries, then you would specify `-b arm-elf` to run that cross compiler. Because there are other options beginning with `-b`, the configuration must contain a hyphen, or `-b` alone should be one argument followed by the configuration in the next argument.

`-V` version
  The argument version specifies which version of GCC to run. This is useful when multiple versions are installed. For example, version might be ‘`4.0`’, meaning to run GCC version 4.0.

The `-V` and `-b` options work by running the `<machine>-gcc-<version>` executable, so there's no real reason to use them if you can just run that directly.