On Sun, Nov 19, 2023 at 11:03:54AM -0600, Dan Hoffman wrote: > On Sun, Nov 19, 2023 at 1:23 AM Michael S. Tsirkin <m...@redhat.com> wrote: > > > > On Sat, Nov 18, 2023 at 10:25:31AM -0800, Daniel Hoffman wrote: > > > `kvm_enabled()` is compiled down to `0` and short-circuit logic is > > > used to remmove references to undefined symbols at the compile stage. > > > Some build configurations with some compilers don't attempt to > > > simplify this logic down in some cases (the pattern appears to be > > > that the literal false must be the first term) and this was causing > > > some builds to emit references to undefined symbols. > > > > > > Signed-off-by: Daniel Hoffman <dhoff...@gmail.com> > > > > Could we add a bit more detail here? Will help make sure > > this does not break again in the future. > > The configuration script was ran as such: ../configure > --without-default-features --target-list=x86_64-softmmu,i386-softmmu > --enable-debug --enable-tcg-interpreter --enable-debug-tcg > --enable-debug-mutex > > I'm pretty sure the only relevant flags here are > --without-default-features, --target-list including x86_64-softmmu and > --enable-debug > > The only error I see is this: [...]/hw/i386/x86.c:422:(.text+0x1004): > undefined reference to `kvm_hv_vpindex_settable' (the other > kvm_enabled() was moved for the sake of consistency). My compiler is > clang (16.0.6). > > I haven't looked into the heuristics or logic for how the compile-time > short-circuit logic works, but I assumed only the first parameter is > "guaranteed" to be checked for a literal false (guaranteed is in > quotes because that's just how clang works, not because it's a feature > of the language IIRC). > > This pattern relies on somes subtle behavior with the compiler, so my > suggestion going forward would be to not rely on code optimizations > removing undefined references based on short-circuit logic (instead > have some configuration macro defined that disables all relevant > code). I'm a new contributor, so I submitted the minimum to make it > work on my machine. > > If you have any other questions, please let me know. > > Thanks!
which compiler is this? -- MST
