On 4/18/2017 2:06 PM, Mojca Miklavec wrote: > Hi, > > On 18 April 2017 at 18:47, Jan Engelhardt wrote: >> On Tuesday 2017-04-18 17:44, Mojca Miklavec wrote: >>> On 18 April 2017 at 17:27, Jan Engelhardt wrote: >>>> >>>> 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. > > No, the idea is not to use the native compiler. > > From a random example using AC_TRY_RUN([...]) the configure script > compiles the code for the host platform, runs it and checks whether > the resulting binary crashes. The idea is to check the binary for > *host* platform, not the guest. > > The autotools need to know whether the will actually run the code or > not. When cross-compiling, the autotools cannot simply run the > resulting binary and the result has to be guessed or a database of all > features of all platforms needs to be present. When compiling > natively, the code can easily run. > > If I use --host=powerpc-<whatever> on x86_64, how can autotools decide > whether or not powerpc binaries can run or not? > >>> 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. > > On Macs (10.4 - 10.5) it works automatically without any qemu magic > (there is some rosetta-something in the background, but that's fully > transparent for users). >
Forgive the brief interlude without any trial of the idea but if you specify the --build the same as the --host for this scenario does it work for you? If I understand correctly you're looking for something similar to executing a 32bit binary in a 64bit world where the OS adjusts for the 32bits in its 64bitness. The idea is that specifying the --host and --build to be the same triplet the configure would execute the resulting binary in tests and the compiler choice would be based on the --host triplet. > > But in order not to get too off-topic: is anything about my proposed > patch actually problematic? > I haven't looked at the patch, I don't know. -- Earnie _______________________________________________ config-patches mailing list config-patches@gnu.org https://lists.gnu.org/mailman/listinfo/config-patches
