Recover from Jython interpreter init failure during constant folding

jython/com.ibm.wala.cast.python.jython3/source/com/ibm/wala/cast/python/loader/Python3Loader.java

@@ -38,6 +38,7 @@
 import org.python.core.PyObject;
 import org.python.core.PySyntaxError;
 import org.python.core.PyUnicode;
+import org.python.util.PythonInterpreter;
 
 public class Python3Loader extends PythonLoader {
 
@@ -102,14 +103,23 @@ public ConstantFoldingRewriter createCAstRewriter(CAst ast) {
               @Override
               protected Object eval(CAstOperator op, Object lhs, Object rhs) {
                 String s = lhs + " " + op.getValue() + " " + rhs;
+
+                PythonInterpreter ip = Python3Interpreter.getInterp();
+                if (ip == null) {
+                  // Jython init failed (memoized in Python3Interpreter). Skip constant folding
+                  // for this expression; analysis remains correct, just less precise. Don't log
+                  // an "Evaluating:" entry — nothing is actually evaluated, and the underlying
+                  // init failure was already announced from getInterp().
+                  return null;
+                }
                 logger.info(() -> "Evaluating: " + s);
 
                 // Use the Python interpreter to evaluate the expression.
                 PyUnicode unicode = new PyUnicode(s);
                 PyObject x;
 
                 try {
-                  x = Python3Interpreter.getInterp().eval(unicode);
+                  x = ip.eval(unicode);
                 } catch (PySyntaxError e) {
                   // Handle syntax errors gracefully.
                   logger.log(WARNING, e, () -> "Syntax error in expression: " + unicode);

jython/com.ibm.wala.cast.python.jython3/source/com/ibm/wala/cast/python/util/Python3Interpreter.java

@@ -1,5 +1,6 @@
 package com.ibm.wala.cast.python.util;
 
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.python.core.PyException;
@@ -13,17 +14,86 @@ public class Python3Interpreter extends com.ibm.wala.cast.python.util.PythonInte
 
   private static PythonInterpreter interp;
 
-  public static PythonInterpreter getInterp() {
+  /**
+   * Memoizes a failed Jython init so subsequent {@link #getInterp()} calls return {@code null}
+   * cheaply instead of re-running {@code new PythonInterpreter()} (which can be expensive when it
+   * fails — site-import walks the Jython resource path on every attempt). When a single failure has
+   * occurred, callers receive {@code null} and can degrade their behavior (e.g., {@link
+   * com.ibm.wala.cast.python.loader.Python3Loader} skips constant folding).
+   */
+  private static volatile boolean initFailed = false;
+
+  /**
+   * Memoizes whether the "interpreter unavailable" warning has already been emitted from {@link
+   * #evalAsInteger(String)}. Without this, callers like {@code interpretAsInt} (invoked many times
+   * during shape inference) would flood logs with one WARNING per call after the first init
+   * failure. The first failure is already announced by the catch block in {@link #getInterp()};
+   * subsequent calls log at FINE level only.
+   *
+   * @implNote Uses {@link AtomicBoolean#compareAndSet} so the check-and-set is atomic. Under
+   *     concurrent call graph construction, multiple threads can race into the {@code if (ip ==
+   *     null)} branch simultaneously; a non-atomic {@code volatile boolean} flag would let several
+   *     of them all pass the check before any sets it, defeating the "log once" intent.
+   */
+  private static final AtomicBoolean unavailableWarned = new AtomicBoolean(false);
+
+  public static synchronized PythonInterpreter getInterp() {
+    if (initFailed) return null;
     if (interp == null) {
-      PySystemState.initialize();
-      interp = new PythonInterpreter();
+      try {
+        PySystemState.initialize();
+        interp = new PythonInterpreter();
+      } catch (Exception t) {
+        // Jython init can fail when bootstrap resources (e.g., the embedded
+        // _frozen_importlib bytecode used by org.python.core.imp) aren't reachable from the
+        // current classloader/working directory. This is environment-dependent (e.g., happens
+        // under Tycho-OSGi but not under plain Maven-surefire). Treat as a recoverable failure:
+        // log once, memoize, and let callers degrade gracefully.
+        //
+        // We catch {@link Exception} (not {@link Throwable}) so that {@link Error} types
+        // (OOM, stack overflow, linkage errors) keep propagating to the caller — those signal
+        // serious VM problems we don't want to silently swallow and continue past.
+        initFailed = true;
+        LOGGER.log(
+            Level.WARNING,
+            t,
+            () ->
+                "Jython interpreter init failed; all interpreter-based evaluation will be disabled"
+                    + " for this run (constant folding in Python3Loader, shape-argument"
+                    + " evaluation via interpretAsInt/evalAsInteger, etc.).");
+        return null;
+      }
     }
     return interp;
   }
 
   public Integer evalAsInteger(String expr) {
+    PythonInterpreter ip = getInterp();
+    if (ip == null) {
+      // Return {@code null} (the same "cannot evaluate" signal used elsewhere in this method's
+      // contract) rather than throwing, so callers like
+      // {@code com.ibm.wala.cast.python.util.PythonInterpreter#interpretAsInt} — which expect a
+      // nullable {@link Integer} and don't catch checked or runtime exceptions — degrade
+      // gracefully in the same OSGi-classloader environments that triggered the {@link
+      // #getInterp()} init failure in the first place.
+      //
+      // Log the first such call at WARNING (so operators see that some shape inference is being
+      // skipped because of the earlier init failure); subsequent calls log at FINE only, since
+      // the underlying init failure has already been announced from {@link #getInterp()}.
+      if (unavailableWarned.compareAndSet(false, true)) {
+        LOGGER.log(
+            Level.WARNING,
+            () ->
+                "Jython interpreter unavailable (init failed earlier); evalAsInteger will return"
+                    + " null for this and any subsequent calls. First skipped expression: "
+                    + expr);
+      } else {
+        LOGGER.log(Level.FINE, () -> "evalAsInteger returning null (interp unavailable): " + expr);
+      }
+      return null;
+    }
     try {
-      PyObject val = getInterp().eval(expr);
+      PyObject val = ip.eval(expr);
       if (val.isInteger()) {
         return val.asInt();
       } else