Index: lldb/source/Expression/UserExpression.cpp
===================================================================
--- lldb/source/Expression/UserExpression.cpp
+++ lldb/source/Expression/UserExpression.cpp
@@ -39,6 +39,7 @@
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/LLDBLog.h"
 #include "lldb/Utility/Log.h"
+#include "lldb/Utility/State.h"
 #include "lldb/Utility/StreamString.h"
 
 using namespace lldb_private;
@@ -205,8 +206,10 @@
   // Since we might need to call allocate memory and maybe call code to make
   // the caller, we need to be stopped.
   if (process != nullptr && process->GetState() != lldb::eStateStopped) {
-    error.SetErrorString("Can't make a function caller while the process is " 
-                          "running");
+    error.SetErrorStringWithFormatv(
+        "Can't make a function caller while the process is {0}: the process "
+        "must be stopped to allocate memory.",
+        StateAsCString(process->GetState()));
     return execution_results;
   }
 
Index: lldb/source/Expression/UtilityFunction.cpp
===================================================================
--- lldb/source/Expression/UtilityFunction.cpp
+++ lldb/source/Expression/UtilityFunction.cpp
@@ -21,6 +21,7 @@
 #include "lldb/Target/Target.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/Log.h"
+#include "lldb/Utility/State.h"
 #include "lldb/Utility/Stream.h"
 
 using namespace lldb_private;
@@ -67,8 +68,10 @@
   // Since we might need to call allocate memory and maybe call code to make
   // the caller, we need to be stopped.
   if (process_sp->GetState() != lldb::eStateStopped) {
-    error.SetErrorString("Can't make a function caller while the process is " 
-                         "running");
+    error.SetErrorStringWithFormatv(
+        "Can't make a function caller while the process is {0}: the process "
+        "must be stopped to allocate memory.",
+        StateAsCString(process_sp->GetState()));
     return nullptr;
   }
 
Index: lldb/test/Shell/Expr/TestFunctionCaller.test
===================================================================
--- /dev/null
+++ lldb/test/Shell/Expr/TestFunctionCaller.test
@@ -0,0 +1,3 @@
+# RUN: %clangxx_host %p/Inputs/call-function.cpp -g -o %t
+# RUN: %lldb %t -o 'r' -o 'expr strlen("")' | FileCheck %s
+# CHECK: error: Can't make a function caller while the process is exited: the process must be stopped to allocate memory.