On Wed, Aug 03, 2022 at 04:10:53PM +0000, Sean Christopherson wrote: > On Wed, Aug 03, 2022, Andrew Jones wrote: > > On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote: > > > My ldd version is (GNU libc) 2.28, and I get a compilation error in this case. > > > But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine. > > > This shows that compilation errors may occur in different GNU libc environments. > > > Would it be more appropriate to use syscall for better compatibility? > > > > OK, it's a pity, but no big deal to use syscall(). > > Ya, https://man7.org/linux/man-pages/man2/gettid.2.html says: > > The gettid() system call first appeared on Linux in kernel 2.4.11. Library > support was added in glibc 2.30. > > But there are already two other instances of syscall(SYS_gettid) in KVM selftests, > tools/testing/selftests/kvm/lib/assert.c even adds a _gettid() wrapper. Ha! And I found four more in selftests... testing/selftests/powerpc/include/utils.h testing/selftests/proc/proc.h testing/selftests/rseq/param_test.c testing/selftests/sched/cs_prctl_test.c and even more in tools... > > So rather than having to remember (or discover) to use syscall(SYS_gettid), I wonder > if it's possible to conditionally define gettid()? E.g. check for GLIBC version? > Or do > > #define gettid() syscall(SYS_gettid) > > so that it's always available and simply overrides the library's gettid() if it's > provided? Sounds good to me. Now the question is where to put it? kvm_util.h, test_util.h, or maybe we should create a new header just for stuff like this? It doesn't really "fit" in kvm_util.h, but if we put it there, then we greatly reduce the chance that we'll have to revisit this issue again. We could also create a new header just for stuff like this and then include that from kvm_util.h... Thanks, drew
