On 11.11.13 22:02, Peter Maydell wrote: > On 11 November 2013 20:10, Andreas Tobler <andre...@freebsd.org> wrote: >> Paolo asked me to test and submit the below patch to fix compilation and >> link with clang. >> >> Paolo reduced the issue to a clang bug where dead code is not properly >> eliminated before linktime. (the clang bug ID: 17882) > > Thanks for the patch. However, it looks a bit odd to me. Can > you quote the error message clang produces, please?
[tcx58:build/qemu/objdir] andreast% gmake CC x86_64-softmmu/target-i386/cpu.o LINK x86_64-softmmu/qemu-system-x86_64 target-i386/cpu.o: In function `cpu_x86_cpuid': /export/devel/net/src/qemu/qemu-master/target-i386/cpu.c:2203: undefined reference to `kvm_arch_get_supported_cpuid' /export/devel/net/src/qemu/qemu-master/target-i386/cpu.c:2204: undefined reference to `kvm_arch_get_supported_cpuid' /export/devel/net/src/qemu/qemu-master/target-i386/cpu.c:2223: undefined reference to `kvm_arch_get_supported_cpuid' cc: error: linker command failed with exit code 1 (use -v to see invocation) gmake[1]: *** [qemu-system-x86_64] Error 1 gmake: *** [subdir-x86_64-softmmu] Error 2 > I think I would agree with the commenter in the bug report you > reference (http://llvm.org/bugs/show_bug.cgi?id=17882) > that this is not a clang bug. We shouldn't be relying on the > compiler's dead code elimination to get rid of references to > functions that don't exist in certain configurations. This will > always be unreliable (especially if compiling without optimization). > Instead we should either be using ifdefs or stub functions (probably > the latter in this case). I know it is a difficult business. And probably you're right, but from a dump users point of view I do not agree. I'm used to gcc, which is able to compile this, and I expect other compilers to be able to do the same. The compiler should work for me not vice versa :) > If you put a stub implementation of kvm_arch_get_supported_cpuid() > into target-i386/kvm-stub.c does this fix the compilation issue? Will try and let you know. Thanks, Andreas
