From 730be651d21f3950980fd61e1c65953017c6322e Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 22 Oct 2019 15:29:48 -0400 Subject: [PATCH] Fix: uninitialized variable in lib_ring_buffer_reserve_committed This internal function implemented in libringbuffer is not used within lttng-ust actually, but uses an uninitialized variable: As reported by clang: ./frontend_internal.h:263:75: warning: variable 'idx' is uninitialized when used here [-Wuninitialized] struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx); ^~~ ./shm.h:74:86: note: expanded from macro 'shmp_index' ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret)); \ ^~~~~ ./frontend_internal.h:262:27: note: initialize the variable 'idx' to silence this warning unsigned long offset, idx, commit_count; ^ = 0 In file included from ring_buffer_backend.c:29: In file included from ./backend.h:33: ./frontend_internal.h:263:75: warning: variable 'idx' is uninitialized when used here [-Wuninitialized] struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx); ^~~ ./shm.h:74:86: note: expanded from macro 'shmp_index' ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret)); \ ^~~~~ ./frontend_internal.h:262:27: note: initialize the variable 'idx' to silence this warning unsigned long offset, idx, commit_count; ^ = 0 Signed-off-by: Mathieu Desnoyers --- libringbuffer/frontend_internal.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h index 4ad921ec..1a9c2d4b 100644 --- a/libringbuffer/frontend_internal.h +++ b/libringbuffer/frontend_internal.h @@ -260,14 +260,11 @@ int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_con struct lttng_ust_shm_handle *handle) { unsigned long offset, idx, commit_count; - struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx); + struct commit_counters_hot *cc_hot; CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); - if (caa_unlikely(!cc_hot)) - return 0; - /* * Read offset and commit count in a loop so they are both read * atomically wrt interrupts. By deal with interrupt concurrency by @@ -279,6 +276,9 @@ int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_con do { offset = v_read(config, &buf->offset); idx = subbuf_index(offset, chan); + cc_hot = shmp_index(handle, buf->commit_hot, idx); + if (caa_unlikely(!cc_hot)) + return 0; commit_count = v_read(config, &cc_hot->cc); } while (offset != v_read(config, &buf->offset)); -- 2.34.1