Fix compiler warning in debug.c
diff --git a/library/debug.c b/library/debug.c
index a9cd814..f9229b3 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -71,7 +71,7 @@
*/
#if defined(MBEDTLS_THREADING_C)
char idstr[20 + DEBUG_BUF_SIZE]; /* 0x + 16 nibbles + ': ' */
- mbedtls_snprintf( idstr, sizeof( idstr ), "%p: %s", ssl, str );
+ mbedtls_snprintf( idstr, sizeof( idstr ), "%p: %s", (void*)ssl, str );
ssl->conf->f_dbg( ssl->conf->p_dbg, level, file, line, idstr );
#else
ssl->conf->f_dbg( ssl->conf->p_dbg, level, file, line, str );