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Merge branch 'selftests-bpf-fix-expression-result-unused-warnings-with-icecc'

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Ilya Leoshkevich says:

====================
selftests/bpf: Fix "expression result unused" warnings with icecc

v3: https://lore.kernel.org/bpf/20250827194929.416969-1-iii@linux.ibm.com/
v3 -> v4: Go back to the original solution (Yonghong, Alexei).

v2: https://lore.kernel.org/bpf/20250827130519.411700-1-iii@linux.ibm.com/
v2 -> v3: Do not touch libbpf, explain how having two function
          declarations works (Andrii).
          Fix bpf-gcc build (CI).

v1: https://lore.kernel.org/bpf/20250508113804.304665-1-iii@linux.ibm.com/
v1 -> v2: Annotate bpf_obj_new_impl() with __must_check (Alexei).
          Add an explanation about icecc.

I took another look at the "expression result unused" warnings I've
been seeing, and it turned out that the root cause was the icecc
compiler wrapper and what I consider a clang bug. Back then I've
reported that the problem was reproducible with plain clang, but now
I see that it was clearly a mixup, sorry about that.

The solution is to add a few awkward (void) casts. I've added a
detailed explanation of why they are helpful to the commit message.
====================

Link: https://patch.msgid.link/20250829030017.102615-1-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov
2025-08-29 11:22:15 -07:00
parent 3aa9b9a165 5d40c038c8
commit 387be23a95
2 changed files with 4 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h
View File

@@ -302,7 +302,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
* barriers.
*/
if (val & _Q_LOCKED_MASK)
smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
(void)smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
/*
* take ownership and clear the pending bit.
@@ -380,7 +380,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
/* Link @node into the waitqueue. */
WRITE_ONCE(prev->next, node);
arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
(void)arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
/*
* While waiting for the MCS lock, the next pointer may have

5
tools/testing/selftests/bpf/progs/linked_list_fail.c
View File

@@ -226,8 +226,7 @@ int obj_new_no_composite(void *ctx)
SEC("?tc")
int obj_new_no_struct(void *ctx)
{
bpf_obj_new(union { int data; unsigned udata; });
(void)bpf_obj_new(union { int data; unsigned udata; });
return 0;
}
@@ -252,7 +251,7 @@ int new_null_ret(void *ctx)
SEC("?tc")
int obj_new_acq(void *ctx)
{
bpf_obj_new(struct foo);
(void)bpf_obj_new(struct foo);
return 0;
}