From 97fb54d86d2194ea8a4cbe6cf074e6ba47b054ea Mon Sep 17 00:00:00 2001 From: "Jose E. Marchesi" Date: Tue, 6 Jan 2026 18:36:49 +0100 Subject: bpf: adapt selftests to GCC 16 -Wunused-but-set-variable GCC 16 has changed the semantics of -Wunused-but-set-variable, as well as introducing new options -Wunused-but-set-variable={0,1,2,3} to adjust the level of support. One of the changes is that GCC now treats 'sum += 1' and 'sum++' as non-usage, whereas clang (and GCC < 16) considers the first as usage and the second as non-usage, which is sort of inconsistent. The GCC 16 -Wunused-but-set-variable=2 option implements the previous semantics of -Wunused-but-set-variable, but since it is a new option, it cannot be used unconditionally for forward-compatibility, just for backwards-compatibility. So this patch adds pragmas to the two self-tests impacted by this, progs/free_timer.c and progs/rcu_read_lock.c, to make gcc to ignore -Wunused-but-set-variable warnings when compiling them with GCC > 15. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44677#c25 for details on why this regression got introduced in GCC upstream. Signed-off-by: Jose E. Marchesi Cc: david.faust@oracle.com Cc: cupertino.miranda@oracle.com Cc: Eduard Zingerman Cc: Yonghong Song Link: https://lore.kernel.org/r/20260106173650.18191-2-jose.marchesi@oracle.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/free_timer.c | 10 ++++++++++ tools/testing/selftests/bpf/progs/rcu_read_lock.c | 10 ++++++++++ 2 files changed, 20 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/free_timer.c b/tools/testing/selftests/bpf/progs/free_timer.c index 4501ae8fc414..eccb2d47db43 100644 --- a/tools/testing/selftests/bpf/progs/free_timer.c +++ b/tools/testing/selftests/bpf/progs/free_timer.c @@ -7,6 +7,16 @@ #define MAX_ENTRIES 8 +/* clang considers 'sum += 1' as usage but 'sum++' as non-usage. GCC + * is more consistent and considers both 'sum += 1' and 'sum++' as + * non-usage. This triggers warnings in the functions below. + * + * Starting with GCC 16 -Wunused-but-set-variable=2 can be used to + * mimic clang's behavior. */ +#if !defined(__clang__) && __GNUC__ > 15 +#pragma GCC diagnostic ignored "-Wunused-but-set-variable" +#endif + struct map_value { struct bpf_timer timer; }; diff --git a/tools/testing/selftests/bpf/progs/rcu_read_lock.c b/tools/testing/selftests/bpf/progs/rcu_read_lock.c index d70c28824bbe..b4e073168fb1 100644 --- a/tools/testing/selftests/bpf/progs/rcu_read_lock.c +++ b/tools/testing/selftests/bpf/progs/rcu_read_lock.c @@ -7,6 +7,16 @@ #include "bpf_tracing_net.h" #include "bpf_misc.h" +/* clang considers 'sum += 1' as usage but 'sum++' as non-usage. GCC + * is more consistent and considers both 'sum += 1' and 'sum++' as + * non-usage. This triggers warnings in the functions below. + * + * Starting with GCC 16 -Wunused-but-set-variable=2 can be used to + * mimic clang's behavior. */ +#if !defined(__clang__) && __GNUC__ > 15 +#pragma GCC diagnostic ignored "-Wunused-but-set-variable" +#endif + char _license[] SEC("license") = "GPL"; struct { -- cgit v1.2.3