[pulseaudio-discuss] [PATCH] alsa-mixer: Improve workaround for Valgrind's false warnings

[David Henningsson]

Valgrind is not correctly handling ALSA TLV syscalls, which leads
to false warnings, looking like this:
 "Conditional jump or move depends on uninitialised value(s)"

Unfortunately, alsa-lib itself also uses these values which valgrind
falsely believe are uninitialized, so not all warnings are removed,
but this is what we can do from PA until the valgrind bug is fixed.

Signed-off-by: David Henningsson <david.henningsson at canonical.com>
---
 src/modules/alsa/alsa-mixer.c | 61 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 52 insertions(+), 9 deletions(-)

diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c
index ead601a..201f835 100644
--- a/src/modules/alsa/alsa-mixer.c
+++ b/src/modules/alsa/alsa-mixer.c
@@ -50,6 +50,58 @@
 #include "alsa-mixer.h"
 #include "alsa-util.h"
 
+#ifdef HAVE_VALGRIND_MEMCHECK_H
+/* These macros are workarounds for a bug in valgrind, which is not handling the
+ * ALSA TLV syscalls correctly. See
+ * http://valgrind.10908.n7.nabble.com/Missing-ioctl-for-SNDRV-CTL-IOCTL-TLV-READ-td42711.html */
+
+static inline int vgfix_get_capture_dB(snd_mixer_elem_t *a, snd_mixer_selem_channel_id_t b, long *c) {
+    int r = snd_mixer_selem_get_capture_dB(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+static inline int vgfix_get_playback_dB(snd_mixer_elem_t *a, snd_mixer_selem_channel_id_t b, long *c) {
+    int r = snd_mixer_selem_get_playback_dB(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+static inline int vgfix_ask_capture_vol_dB(snd_mixer_elem_t *a, long b, long *c) {
+    int r = snd_mixer_selem_ask_capture_vol_dB(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+static inline int vgfix_ask_playback_vol_dB(snd_mixer_elem_t *a, long b, long *c) {
+    int r = snd_mixer_selem_ask_playback_vol_dB(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+static inline int vgfix_get_capture_dB_range(snd_mixer_elem_t *a, long *b, long *c) {
+    int r = snd_mixer_selem_get_capture_dB_range(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(b, sizeof(*b));
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+static inline int vgfix_get_playback_dB_range(snd_mixer_elem_t *a, long *b, long *c) {
+    int r = snd_mixer_selem_get_playback_dB_range(a, b, c);
+    VALGRIND_MAKE_MEM_DEFINED(b, sizeof(*b));
+    VALGRIND_MAKE_MEM_DEFINED(c, sizeof(*c));
+    return r;
+}
+
+#define snd_mixer_selem_get_capture_dB(a, b, c) vgfix_get_capture_dB(a, b, c)
+#define snd_mixer_selem_get_playback_dB(a, b, c) vgfix_get_playback_dB(a, b, c)
+#define snd_mixer_selem_ask_capture_vol_dB(a, b, c) vgfix_ask_capture_vol_dB(a, b, c)
+#define snd_mixer_selem_ask_playback_vol_dB(a, b, c) vgfix_ask_playback_vol_dB(a, b, c)
+#define snd_mixer_selem_get_capture_dB_range(a, b, c) vgfix_get_capture_dB_range(a, b, c)
+#define snd_mixer_selem_get_playback_dB_range(a, b, c) vgfix_get_playback_dB_range(a, b, c)
+
+#endif
+
 static int setting_select(pa_alsa_setting *s, snd_mixer_t *m);
 
 struct description_map {
@@ -1001,10 +1053,6 @@ static int element_set_volume(pa_alsa_element *e, snd_mixer_t *m, const pa_chann
             if (r < 0)
                 continue;
 
-#ifdef HAVE_VALGRIND_MEMCHECK_H
-            VALGRIND_MAKE_MEM_DEFINED(&value, sizeof(value));
-#endif
-
             f = from_alsa_dB(value);
 
         } else {
@@ -1517,11 +1565,6 @@ static int element_probe(pa_alsa_element *e, snd_mixer_t *m) {
                 }
 
                 if (e->has_dB) {
-#ifdef HAVE_VALGRIND_MEMCHECK_H
-                    VALGRIND_MAKE_MEM_DEFINED(&min_dB, sizeof(min_dB));
-                    VALGRIND_MAKE_MEM_DEFINED(&max_dB, sizeof(max_dB));
-#endif
-
                     e->min_dB = ((double) min_dB) / 100.0;
                     e->max_dB = ((double) max_dB) / 100.0;
 
-- 
1.9.1