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Work around a false positive compiler warning in pcm_switch_sink()

Browse source 
CC firmware/pcm.c
firmware/pcm.c: In function ‘pcm_switch_sink’:
firmware/pcm.c:311:38: warning: array subscript 1 is above array bounds of ‘struct pcm_sink *[1]’ [-Warray-bounds]
  311 |     struct pcm_sink* old_sink = sinks[cur_sink];
      |                                 ~~~~~^~~~~~~~~~
firmware/pcm.c:79:25: note: while referencing ‘sinks’
   79 | static struct pcm_sink* sinks[PCM_SINK_NUM] = {
      |

PCM_SINK_NUM is 1, and cur_sink is initialized to 0.  It can never be set
above 0.  cur_sink can never be >= PCM_SINK_NUM, ie 0, but for some reason
the compiler thinks otherwise.... sometimes.

This only shows up on native ARM builds with GCC9.5.0

Change-Id: I1aa731a4ee21c46a264c8b70833e3b43e777e8a7
This commit is contained in:
Solomon Peachy 2026-04-17 21:42:08 -04:00
parent 39abe4f698
commit 9dce0c3258
2 changed files with 20 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

1
firmware/export/pcm_sink.h
View file

@ -52,6 +52,7 @@ struct pcm_sink {
enum pcm_sink_ids {
PCM_SINK_BUILTIN = 0,
PCM_SINK_NUM
};
/* defined in each platform pcm source */

23
firmware/pcm.c
View file

@ -21,6 +21,7 @@
#include <stdlib.h>
#include "system.h"
#include "kernel.h"
#include "panic.h"
/* Define LOGF_ENABLE to enable logf output in this file */
//#define LOGF_ENABLE
@ -76,7 +77,7 @@
*
*/
static struct pcm_sink* sinks[1] = {
static struct pcm_sink* sinks[PCM_SINK_NUM] = {
[PCM_SINK_BUILTIN] = &builtin_pcm_sink,
};
static enum pcm_sink_ids cur_sink = PCM_SINK_BUILTIN;
@ -247,7 +248,7 @@ void pcm_init(void)
{
logf("pcm_init");
for(size_t i = 0; i < ARRAYLEN(sinks); i += 1) {
for(size_t i = 0; i < PCM_SINK_NUM; i += 1) {
struct pcm_sink* sink = sinks[i];
sink->pending_freq = sink->caps.default_freq;
sink->configured_freq = -1U;
@ -261,7 +262,7 @@ void pcm_postinit(void)
{
logf("pcm_postinit");
for(size_t i = 0; i < ARRAYLEN(sinks); i += 1) {
for(size_t i = 0; i < PCM_SINK_NUM; i += 1) {
struct pcm_sink* sink = sinks[i];
sink->ops.postinit();
sink->pcm_is_ready = true;
@ -294,15 +295,29 @@ const struct pcm_sink_caps* pcm_current_sink_caps(void)
bool pcm_switch_sink(enum pcm_sink_ids sink)
{
logf("pcm_switch_sink %d to %d", cur_sink, sink);
if(sink >= ARRAYLEN(sinks)) {
if(sink >= PCM_SINK_NUM) {
return false;
}
if(cur_sink == sink) {
return true;
}
/* This should not be possible but it silences
a false warning that only occurs with with GCC9.5 on bare metal ARM.
*/
#if __GNUC__ == 9 && defined(CPU_ARM)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Warray-bounds"
#endif
/* save current sink before switching */
struct pcm_sink* old_sink = sinks[cur_sink];
#if __GNUC__ == 9
#pragma GCC diagnostic pop
#endif
/* update sink index */
cur_sink = sink;
/* synchronize frequency */