Harden test and self-segfault causing native posix method

Author: timfel

graalpython/com.oracle.graal.python.test/src/tests/test_traceback.py

@@ -664,7 +664,7 @@ def test_faulthandler_sigsegv_builtin():
     import faulthandler
 
     try:
-        if not __graalpython__.is_native:
+        if not __graalpython__.is_native or __graalpython__.posix_module_backend() == "java":
             return
     except NameError:
         pass # CPython

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

@@ -1170,7 +1170,7 @@ public void kill(long pid, int signal,
     public void signalSelf(int signal,
                     @Shared("invoke") @Cached InvokeNativeFunction invokeNode) throws PosixException {
         if (!ImageInfo.inImageRuntimeCode()) {
-            throw new UnsupportedPosixFeatureException("faulthandler self-signals are only supported in native standalone");
+            throw new UnsupportedPosixFeatureException("self-signals are only supported in native standalone");
         }
         int res = invokeNode.callInt(this, PosixNativeFunction.signal_self, signal);
         if (res == -1) {

graalpython/python-libposix/src/posix.c

@@ -77,6 +77,8 @@
 #include <unistd.h>
 #include <pwd.h>
 
+int32_t signal_self_segv(void);
+
 #ifdef __APPLE__
 #include <util.h>
 #else
@@ -608,8 +610,7 @@ int32_t signal_self(int32_t signal) {
             abort();
             break;
         case SIGSEGV:
-            *((volatile int *)0) = 1;
-            break;
+            return signal_self_segv();
         default:
             errno = EINVAL;
             return -1;

graalpython/python-libposix/src/posix_signal_self_segv.c

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2020, 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stdint.h>
+
+#if defined(_MSC_VER)
+#pragma optimize("", off)
+#define SIGNAL_SELF_SEGV_ATTR __declspec(noinline)
+#elif defined(__clang__)
+#pragma clang optimize off
+#define SIGNAL_SELF_SEGV_ATTR __attribute__((optnone, noinline))
+#elif defined(__GNUC__)
+#define SIGNAL_SELF_SEGV_ATTR __attribute__((optimize("O0"), noinline, noclone))
+#else
+#define SIGNAL_SELF_SEGV_ATTR
+#endif
+
+/*
+ * Keep the deliberate SIGSEGV in its own translation unit and discourage
+ * inlining/optimization to minimize the optimizer's freedom around the
+ * undefined null-dereference below.
+ */
+SIGNAL_SELF_SEGV_ATTR int32_t signal_self_segv(void) {
+    volatile int *p = (volatile int *)(uintptr_t)0;
+    *p = 1;
+    return 0;
+}
+
+#if defined(_MSC_VER)
+#pragma optimize("", on)
+#elif defined(__clang__)
+#pragma clang optimize on
+#endif