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Re: Patch for config.guess for "cross-compiling" x86_64 -> powerpc on Ma
Re: Patch for config.guess for "cross-compiling" x86_64 -> powerpc on Mac OS X <= 10.6
Tue, 18 Apr 2017 18:47:45 +0200 (CEST)
Alpine 2.21 (LSU 202 2017-01-01)
On Tuesday 2017-04-18 17:44, Mojca Miklavec wrote:
>On 18 April 2017 at 17:27, Jan Engelhardt wrote:
>> On Tuesday 2017-04-18 17:18, Mojca Miklavec wrote:
>>>I would like to request a patch for config.guess to partially address
>>>some problems experienced when setting
>>> CC="gcc -arch ppc"
>>>on Mac OS X 10.4-10.6 i386 or x86_64.
>> At least on my side of the ocean, when cross-compiling, specifying the
>> triplet is the correct way.
>> ./configure --host=powerpc-unknown-linux-gnu
>Do you also run
> ./configure --host=i686-unknown-linux-gnu
>when you want to compile 32-bit binaries on 64-bit linux?
Well yes, and I have a number of different possible answers as to
1. Because i686 is different ISA from AMD64.
2. If you were to only use CFLAGS=-m32, you would get a 32-bit binary
in the current ISA(*). This holds true for SPARC, powerpc and more
targets. (Possibly even ARMv8-A/aarch64, have not checked that yet.)
(*) The only exception is the x86_64 gcc where, due to historical
reasons, the 32-bit AMD64 mode is selected with -mx32 instead.
3. Distributions also pass --host all the time -- it tends to
affects paths (think usr/lib/perl5/5.8.12/i386-linux-thread-multi and
/usr/lib/i386-linux-gnu on some Linux distros).
If you were to omit --host=i686 and specify just CFLAGS=-m32, autoconf would
default to your current platform (assuming x86_64-linux) and you will
a. possibly end up installing an unwanted binary format into a x86_64 directory
b. have a "-m32"/"-mx32" binary load configuration files from a
x86_64 path meant for an x86_64 environment.
>> That will invoke /usr/bin/powerpc-unknown-linux-gnu-gcc etc., which can
>> be the PPC compiler, or a shell script invoking an existing native-by-default
>> gcc with more arguments.
>The problem of this approach is that the configure scripts etc. then
>assume that the computer where you run the configuration is not able
>to run the resulting binaries.
Yes, that is a bit unfortunate -- but usually points to a problem
*elsewhere*. If a software package needs, say, an utility to generate
more source code from an IDL [think protobuf], the package in
question should ensure it uses the native compiler for these things.
I also acknowledge that autotools does not expose the native CC very
>Building for i386 or ppc is not really cross-compiling in the
>traditional sense. An x86_64 machine can still run the ppc binaries
Last time I tried, x86_64 chips only support the i686 and AMD64 ISAs
natively. For something like ppc, one would need a binfmt_misc(5)
entry with some qemu magic attached.
>(And if that was true ... why is then config.guess calling the
>compiler to differentiate between 32-bit and 64-bit darwin instead of
>simply asking the OS whether it's 64-bit capable?)
I never groked that part either. Maybe because some OSes did
not hand out that information through the normal channels?
Re: Patch for config.guess for "cross-compiling" x86_64 -> powerpc on Mac OS X <= 10.6, Bruno Haible, 2017/04/19