From 650941cdf590b4290a3c8c4cb5ecb4c7f74bea02 Mon Sep 17 00:00:00 2001
From: Joel Dice <joel.dice@gmail.com>
Date: Fri, 16 Sep 2016 13:55:09 -0600
Subject: [PATCH] print informative message if lambda encountered with no host
 VM

Per a recent bug report in the hello-ios project, we found that
bootimage-generator would abort with no explanation if it encountered
a lambda invocation and the `-hostvm` option was unspecified.  This
commit ensures that a helpful message is printed before exiting.
---
 src/compile.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/compile.cpp b/src/compile.cpp
index 08444e2644..97240fbb89 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -5140,6 +5140,14 @@ loop:
         PROTECT(t, bootstrapArray);
 
         if (isLambda(t, c->loader(), bootstrapArray, invocation)) {
+          if (bc->hostVM == 0) {
+            throwNew(t,
+                     GcVirtualMachineError::Type,
+                     "lambda expression encountered, but host VM is not "
+                     "available; use -hostvm option to bootimage-generator to "
+                     "fix this");
+          }
+
           JNIEnv* e;
           if (bc->hostVM->vtable->AttachCurrentThread(bc->hostVM, &e, 0) == 0) {
             e->vtable->PushLocalFrame(e, 256);