mpcm: Add volatile to some fields

src/lib/mpmc.c

@@ -10,7 +10,7 @@
 
 static void *mpmc_worker(void *arg);
 
-int mpmc_init(mpmc_t *ctx, int n_workers, int buf_size, void (*consumer)(void *obj), const char *name) {
+int mpmc_init(mpmc_t *ctx, const int n_workers, const int buf_size, void (*consumer)(void *), const char *name) {
     ctx->alive = 1;
     ctx->n_workers = n_workers;
     ctx->size = buf_size, ctx->max_size = buf_size;
@@ -72,7 +72,7 @@ int mpmc_queue(mpmc_t *ctx, void *obj) {
         }
     }
 
-    int p = ctx->wr;
+    const int p = ctx->wr;
     ctx->wr = (ctx->wr + 1) % ctx->size;
 
     // unlock wr field
@@ -121,14 +121,14 @@ static void *mpmc_worker(void *arg) {
             }
         }
 
-        int p = ctx->rd;
+        const int p = ctx->rd;
         ctx->rd = (ctx->rd + 1) % ctx->size;
 
         // unlock rd field
         sem_post(&ctx->lck_rd);
 
         // consume object
-        ctx->consumer(ctx->buffer[p]);
+        ctx->consumer((void *)ctx->buffer[p]);
         logger_set_prefix("");
 
         // unlock slot in buffer
@@ -143,9 +143,9 @@ void mpmc_stop(mpmc_t *ctx) {
 }
 
 void mpmc_destroy(mpmc_t *ctx) {
-    int e = errno;
+    const int e = errno;
 
-    // stop threads, if running
+    // stop threads if running
     mpmc_stop(ctx);
     for (int i = 0; i < ctx->n_workers; i++) {
         if (ctx->workers[i] == -1) break;

src/lib/mpmc.h

@@ -5,18 +5,18 @@
 #include <semaphore.h>
 
 typedef struct {
-    unsigned char alive;
+    volatile unsigned int alive:1;
     int n_workers;
-    int rd, wr;
+    volatile int rd, wr;
     sem_t free, used, lck_rd, lck_wr;
     int size, max_size;
-    void **buffer;
+    volatile void **buffer;
     pthread_t *workers;
     void (*consumer)(void *obj);
     const char* name;
 } mpmc_t;
 
-int mpmc_init(mpmc_t *ctx, int n_workers, int buf_size, void (*consumer)(void *obj), const char *name);
+int mpmc_init(mpmc_t *ctx, int n_workers, int buf_size, void (*consumer)(void *), const char *name);
 
 int mpmc_queue(mpmc_t *ctx, void *obj);