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 why: 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 when installing 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 >> either >> 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 well.. >Building for i386 or ppc is not really cross-compiling in the >traditional sense. An x86_64 machine can still run the ppc binaries >without problems 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? _______________________________________________ config-patches mailing list config-patches@gnu.org https://lists.gnu.org/mailman/listinfo/config-patches
