From 45bbe274e9f13f935a5e31ba2e7cc46e26495e7f Mon Sep 17 00:00:00 2001
From: Aaron <aaron.long@stfc.ac.uk>
Date: Wed, 12 Feb 2020 11:58:32 +0000
Subject: [PATCH] Error case for NULL arg causing segfault in
 iocshPersistentString

---
 modules/libcom/src/iocsh/iocsh.cpp | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/modules/libcom/src/iocsh/iocsh.cpp b/modules/libcom/src/iocsh/iocsh.cpp
index 8e4d365f9..2341c9b83 100644
--- a/modules/libcom/src/iocsh/iocsh.cpp
+++ b/modules/libcom/src/iocsh/iocsh.cpp
@@ -314,13 +314,18 @@ cvtArg (const char *filename, int lineno, char *arg, iocshArgBuf *argBuf,
         break;
 
     case iocshArgPersistentString:
-        argBuf->sval = (char *) malloc(strlen(arg) + 1);
-        if (argBuf->sval == NULL) {
-            showError(filename, lineno, "Out of memory");
+        if (arg != NULL) {
+            argBuf->sval = (char *) malloc(strlen(arg) + 1);
+            if (argBuf->sval == NULL) {
+                showError(filename, lineno, "Out of memory");
+                return 0;
+            }
+            strcpy(argBuf->sval, arg);
+            break;
+        } else {
+            showError(filename, lineno, "Unable to copy as provided arg was NULL");
             return 0;
         }
-        strcpy(argBuf->sval, arg);
-        break;
 
     case iocshArgPdbbase:
         /* Argument must be missing or 0 or pdbbase */