diff -r e8a0af9fc1cb -r 3a3803a0c789 src/share/vm/compiler/disassembler.cpp
--- a/src/share/vm/compiler/disassembler.cpp	Mon Sep 23 20:26:18 2019 +0200
+++ b/src/share/vm/compiler/disassembler.cpp	Fri Apr 03 14:14:26 2020 +0100
@@ -295,6 +295,7 @@
         strlen((const char*)arg) > sizeof(buffer) - 1) {
       // Only print this when the mach changes
       strncpy(buffer, (const char*)arg, sizeof(buffer) - 1);
+      buffer[sizeof(buffer) - 1] = '\0';
       output()->print_cr("[Disassembling for mach='%s']", arg);
     }
   } else if (match(event, "format bytes-per-line")) {