Prevent endless loop in test.support.reap_children()

Author: otethal

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/PosixModuleBuiltins.java

@@ -1449,13 +1449,8 @@ PTuple waitpid(VirtualFrame frame, int pid, int options) {
                     int exitStatus = getResources().waitpid(pid);
                     return factory().createTuple(new Object[]{pid, exitStatus});
                 } else if (options == WNOHANG) {
-                    int exitStatus = getResources().exitStatus(pid);
-                    if (exitStatus == Integer.MIN_VALUE) {
-                        // not terminated, yet, we should return 0
-                        return factory().createTuple(new Object[]{0, 0});
-                    } else {
-                        return factory().createTuple(new Object[]{pid, exitStatus});
-                    }
+                    int[] res = getResources().exitStatus(pid);
+                    return factory().createTuple(new Object[]{res[0], res[1]});
                 } else {
                     throw raise(PythonBuiltinClassType.NotImplementedError, "Only 0 or WNOHANG are supported for waitpid");
                 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PosixResources.java

@@ -458,13 +458,23 @@ public int waitpid(int pid) throws IndexOutOfBoundsException, InterruptedExcepti
     }
 
     @TruffleBoundary(allowInlining = true)
-    public int exitStatus(int pid) throws IndexOutOfBoundsException {
-        Process process = getChild(pid);
-        if (process.isAlive()) {
-            return Integer.MIN_VALUE;
+    public int[] exitStatus(int pid) throws IndexOutOfBoundsException {
+        if (pid == -1) {
+            for (int childPid = 1; childPid < children.size(); ++childPid) {
+                Process child = children.get(childPid);
+                if (child != null && !child.isAlive()) {
+                    children.set(childPid, null);
+                    return new int[]{childPid, child.exitValue()};
+                }
+            }
         } else {
-            return process.exitValue();
+            Process process = getChild(pid);
+            if (!process.isAlive()) {
+                children.set(pid, null);
+                return new int[]{pid, process.exitValue()};
+            }
         }
+        return new int[]{0, 0};
     }
 
     @TruffleBoundary(allowInlining = true)