Merge branch 'bpf-selftests-fixes-for-gcc-bpf-16'

Jose E. Marchesi says:

====================
bpf: selftests fixes for GCC-BPF 16

Hello.

Just a couple of small fixes to get the BPF selftests build with what
will become GCC 16 this spring.  One of the regressions is due to a
change in the behavior of a warning in GCC 16.  The other is due to
the fact that GCC 16 actually implements btf_decl_tag and
btf_type_tag.

Salud!
====================

Link: https://patch.msgid.link/20260106173650.18191-1-jose.marchesi@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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;
 };

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 {

tools/testing/selftests/bpf/progs/test_btf_decl_tag.c

@@ -33,7 +33,7 @@ struct {
 } hashmap1 SEC(".maps");
 
 
-static __noinline int foo(int x __tag1 __tag2) __tag1 __tag2
+static __noinline __tag1 __tag2 int foo(int x __tag1 __tag2)
 {
 	struct key_t key;
 	value_t val = {};