Subject: Re: Compiling apps to Mingw32 with cygwin
From: "Robert Collins" <[email-masked]>
To: "Jon Leichter" <[email-masked]>
Cc: <[email-masked]>, <[email-masked]>
Date: Fri, 11 Jan 2002 09:27:57 +1100

----- Original Message -----
From: "Jon Leichter" <[email-masked]>

> > No. Specify --host. The meaning is clearly documented in the
autoconf
> > documentation.
> > For clarity:
> > build - what OS the compilation is running on..
> > host  - what OS the binaries created should run on.
> > target - what OS the binaries created should target their output to.
>
> Actually, I'm a little unclear. Are you saying that 'target' is for
binaries
> that you build, which in themselves, generate other binaries? Would an
> example of this be GCC?

Yes. The way they are used is kinda cool. Imagine that you've got a new
platform (say wince). It's got no gcc at the moment, and the c compiler
you've got for it is brain-dead (can't host a two-stage gcc build). You
do have a C library that should build for it.
What you do is:
build gcc+binutils with --build=here --host=here --target=wince
and then build the C library for that platform. Place those libraries in
an appropriate search location (ie /usr/local/lib/wince :})
then you
build gcc+binutils with --build=here --host=wince --target=wince
and then you copy the resulting binaries to the target platform, and
finally can build
gcc as a native 3 step boot strap, to ensure everything is ok. i.e. (for
completeness)
build gcc+binutils with --build=wince --host=wince --target=wince

> Would I still need to "properly" specify --target if
> I wasn't building binaries that generated binaries? Would you then say
that
> the following is the appropriate set of switches for Cygwin-GCC to
produce
> MinGW binaries:

Target can be safely skipped if you know for sure that the package does
not create platform specific output. I'm not saying 'binaries' here
because there are other forms of platform specific output that may
exist.

> --build=i686-pc-cygwin --host=i686-pc-mingw32 --target=i686-pc-mingw32

Yes, that should work. GCC will look for a i686-pc-mingw32 cross
compiler.

> Can I leave out the --build switch? Will it get automatically
resolved? Or

Thats what I said :}. I was wrong (I've just rechecked).

In theory I'm right, but for backward compatability, if you specify
host, but not build, then build is set to host. This is (obviously)
wrong and will eventually get removed. For now specify both build and
host explicitly. (which is a bummer for cross- scripts (because the user
must then know what build is, or the script must duplicate what
config.guess and config.sub do.).

> does that ALSO depend on how well configure.in was written? In the
configure
> scripts I've used, I have consistently seen the 'build' variables get
> assigned the same values as the 'host' variables.

You've seen broken scripts then. There may well be brain damaged scripts
around.

See http://www.gnu.org/manual/autoconf/html_mono/autoconf.html#SEC117

Rob

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