--- a/th_ioctx.c	Thu Dec 26 13:05:40 2019 +0200
+++ b/th_ioctx.c	Thu Dec 26 13:07:09 2019 +0200
@@ -108,7 +108,7 @@
 }
 
 
-void th_io_error_v(th_ioctx *ctx, const int err, const char *fmt, va_list ap)
+int th_io_error_v(th_ioctx *ctx, const int err, const char *fmt, va_list ap)
 {
     char *msg = th_strdup_vprintf(fmt, ap);
 
@@ -118,15 +118,17 @@
         THERR("'%s' #%" PRIu_SIZE_T ": %s\n", ctx->filename, ctx->line, msg);
 
     th_free(msg);
+    return err;
 }
 
 
-void th_io_error(th_ioctx *ctx, const int err, const char *fmt, ...)
+int th_io_error(th_ioctx *ctx, const int err, const char *fmt, ...)
 {
     va_list ap;
     va_start(ap, fmt);
     th_io_error_v(ctx, err, fmt, ap);
     va_end(ap);
+    return err;
 }