Compiler Option Arch

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Compiler Option: -arch

Set target architecture for improved/restricted code generation or cross-compiling

Syntax

-arch < architecture >

Parameters

architecture

The target architecture. Recognized values:

Description

The -arch compiler option sets the target CPU architecture. This can be used for multiple purposes:

The exact impact which the -arch setting has on code generation depends on the code generation backend that is being used. The x86 ASM backend (-gen gas) handles the -arch setting and adjusts code generation accordingly in some cases. When using the GCC backend (-gen gcc), the specified architecture will be passed on to gcc via gcc -march=<...>, causing gcc to generate code for the specified architecture.

However, -arch only affects newly generated code, but not pre-compiled code such as the FreeBASIC runtime libraries, or any other library from the lib/ directory. For example, using -arch 386 is not necessarily enough to get a pure i386 executable -- it also depends on how all the libraries that will be linked in were compiled.

The -arch 32 and -arch 64 shortcuts are similar to gcc's -m32/-m64 options. On 32bit architectures, -arch 64 is an abbreviation for cross-compiling to the default 64bit version of the architecture (e.g. from 32bit x86 to 64bit x86_64, or 32bit ARM to 64bit AArch64, or 32bit PowerPC to 64bit PowerPC), and -arch 32 does nothing. On 64bit systems, it is the other way round: -arch 32 cross-compiles to the default 32bit architecture, while -arch 64 does nothing.

The -arch native shortcut is similar to gcc's -march=native option. On x86, it causes the compiler to try and detect the host CPU automatically based on the cpuid instruction and its availability or results. On other architectures, this will currently simply use the architecture which the compiler itself was built for. Under -gen gcc this will use gcc -march=native.

Specifying an -arch setting incompatible to the native architecture will trigger cross-compilation, just like the -target option, except that only the target architecture, but not the target operating system, is changed.

Version

See also

• Using the Command Line
• -target

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