change to fail on unnecessary hts_set_threads/_pool invocation

Author: vasudeva8

bgzf.c

@@ -1741,6 +1741,8 @@ int bgzf_thread_pool(BGZF *fp, hts_tpool *pool, int qsize) {
     // No gain from multi-threading when not compressed
     if (!fp->is_compressed)
         return 0;
+    if (fp->mt)
+        return -2;  //already exists!
 
     mtaux_t *mt;
     mt = (mtaux_t*)calloc(1, sizeof(mtaux_t));
@@ -1789,9 +1791,10 @@ int bgzf_mt(BGZF *fp, int n_threads, int n_sub_blks)
     if (!p)
         return -1;
 
-    if (bgzf_thread_pool(fp, p, 0) != 0) {
+    int ret = 0;
+    if ((ret = bgzf_thread_pool(fp, p, 0)) < 0) {
         hts_tpool_destroy(p);
-        return -1;
+        return ret;
     }
 
     fp->mt->own_pool = 1;

cram/cram_io.c

@@ -5868,6 +5868,8 @@ int cram_set_voption(cram_fd *fd, enum hts_fmt_option opt, va_list args) {
 
     case CRAM_OPT_NTHREADS: {
         int nthreads =  va_arg(args, int);
+        if (fd->pool)
+            return -2;  //already exists!
         if (nthreads >= 1) {
             if (!(fd->pool = hts_tpool_init(nthreads)))
                 return -1;
@@ -5881,6 +5883,8 @@ int cram_set_voption(cram_fd *fd, enum hts_fmt_option opt, va_list args) {
 
     case CRAM_OPT_THREAD_POOL: {
         htsThreadPool *p = va_arg(args, htsThreadPool *);
+        if (fd->pool)
+            return -2;  //already exists!
         fd->pool = p ? p->pool : NULL;
         if (fd->pool) {
             fd->rqueue = hts_tpool_process_init(fd->pool,

sam.c

@@ -3713,7 +3713,7 @@ static void *sam_format_worker(void *arg) {
 
 int sam_set_thread_pool(htsFile *fp, htsThreadPool *p) {
     if (fp->state)
-        return 0;
+        return -2;   //already exists!
 
     if (!(fp->state = sam_state_create(fp)))
         return -1;
@@ -3747,8 +3747,11 @@ int sam_set_threads(htsFile *fp, int nthreads) {
     p.qsize = nthreads*2;
 
     int ret = sam_set_thread_pool(fp, &p);
-    if (ret < 0)
+    if (ret < 0) {
+        if (p.pool)
+            hts_tpool_destroy(p.pool);
         return ret;
+    }
 
     SAM_state *fd = (SAM_state *)fp->state;
     fd->own_pool = 1;