Re: Difference gcc options "-m32" and "-arch i386"

[Ian Lance Taylor <iant at google dot com>]

info4jpk <info4jpk@googlemail.com> writes:

> Could someone please explain me the difference between the two gcc/g++
> options "-m32" and "-arch i386"? Is there any difference when used as a
> compiler or linker flag?

I quote the friendly manual:

  -m32
  -m64
    Generate code for a 32-bit or 64-bit environment.  The 32-bit
    environment sets int, long and pointer to 32 bits and generates
    code that runs on any i386 system.  The 64-bit environment sets
    int to 32 bits and long and pointer to 64 bits and generates code
    for AMD's x86-64 architecture.  For darwin only the -m64 option
    turns off the -fno-pic and -mdynamic-no-pic options.

  -march=cpu-type
    Generate instructions for the machine type cpu-type.  The choices
    for cpu-type are the same as for -mtune.  Moreover, specifying
    -march=cpu-type implies -mtune=cpu-type.

In other words, selecting -m32 does not necessarily restrict the
compiler to using only instructions which are available on the i386.
Selecting -march=i386 does restrict the compiler.  The default -march
option is determined by how the compiler was configured when it was
built.

Ian