Merge PR #26: Move to GitHub Actions for CI

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: Tests
+
+on: [push, pull_request]
+
+jobs:
+  test_som:
+    runs-on: ubuntu-20.04 # ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          submodules: true
+
+      - name: Tests
+        run: |
+          ant test
+      
+      - name: CheckStyle
+        run: |
+          ant checkstyle
+      
+      - name: Download Eclipse
+        run: |
+          export ECLIPSE_TAR=eclipse.tar.gz
+          export ECLIPSE_URL=https://ftp.halifax.rwth-aachen.de/eclipse/eclipse/downloads/drops4/R-4.17-202009021800/eclipse-SDK-4.17-linux-gtk-x86_64.tar.gz
+          wget ${ECLIPSE_URL} -O ${ECLIPSE_TAR}
+          tar -C ${GITHUB_WORKSPACE}/.. -xzf ${ECLIPSE_TAR}
+          
+      
+      - name: Check Eclipse Format
+        run: |
+          export ECLIPSE_EXE=${GITHUB_WORKSPACE}/../eclipse/eclipse
+          ant eclipseformat

src/som/vm/Universe.java

@@ -661,9 +661,15 @@ public SClass loadClass(final SSymbol name) throws ProgramDefinitionError {
   }
 
   public void loadSystemClass(final SClass systemClass) throws ProgramDefinitionError {
-    // Load the system class
     SClass result = loadClass(systemClass.getName(), systemClass);
 
+    if (result == null) {
+      throw new ProgramDefinitionError("Failed to load the "
+          + systemClass.getName().getEmbeddedString() + " class."
+          + " This is unexpected and may indicate that the classpath is not set correctly,"
+          + " or that the core library is not available.");
+    }
+
     // Load primitives if necessary
     if (result.hasPrimitives()) {
       result.loadPrimitives();