Allow IsolateNativeModules for core modules without a venv

Author: timfel

graalpython/com.oracle.graal.python.test/src/org/graalvm/python/embedding/cext/test/MultiContextCExtTest.java

@@ -243,15 +243,9 @@ public void testCreatingVenvForMulticontext() throws IOException {
             } catch (PolyglotException e) {
                 assertTrue("We rely on sys.prefix", e.getMessage().contains("sys.prefix must be a str"));
             }
-            // Fifth one does not work because we don't have the venv configured
-            try {
-                c5.eval(code);
-                fail("should not reach here");
-            } catch (PolyglotException e) {
-                assertTrue("We need a venv", e.getMessage().contains("sys.prefix must point to a venv"));
-            }
-            // Using a context without isolation in the same process needs to use LLVM
-            assertFalse("have not had a context use LLVM, yet", log.truffleLog.toString().contains("as bitcode"));
+            // Fifth works even without a venv
+            c5.eval(code);
+            // Using a context without isolation in the same process does not work
             try {
                 c0.eval(code);
                 fail("should not reach here");

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/copying/NativeLibraryLocator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2024, 2025, 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
@@ -189,11 +189,31 @@ private static String resolve(PythonContext context, TruffleFile original, int c
         String newName = copyNameOf(original.getName(), capiSlot);
 
         if (original.getAbsoluteFile().startsWith(context.getCoreHome().toJavaStringUncached())) {
-            // must be relocated to venv
+            // must be relocated to venv or tmpdir
             Object sysPrefix = context.getSysModule().getAttribute(T_PREFIX);
             Object sysBasePrefix = context.getSysModule().getAttribute(T_BASE_PREFIX);
             if (sysPrefix.equals(sysBasePrefix)) {
-                throw new ApiInitException(ErrorMessages.SYS_PREFIX_MUST_POINT_TO_A_VENV_FOR_CAPI_ISOLATION);
+                TruffleFile tempDir;
+                try {
+                    tempDir = context.getEnv().createTempDirectory(null, null);
+                } catch (IOException e) {
+                    throw new ApiInitException(ErrorMessages.SYS_PREFIX_MUST_POINT_TO_A_VENV_FOR_CAPI_ISOLATION);
+                }
+                context.registerAtexitHook((ctx) -> {
+                    try {
+                        tempDir.delete();
+                    } catch (IOException e) {
+                        // Nothing we can do at this point
+                    }
+                });
+                copy = tempDir.resolve(newName);
+                context.registerAtexitHook((ctx) -> {
+                    try {
+                        copy.delete();
+                    } catch (IOException e) {
+                        // Nothing we can do at this point
+                    }
+                });
             } else {
                 try {
                     var tsSysPrefix = CastToTruffleStringNode.executeUncached(sysPrefix);

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/ErrorMessages.java

@@ -1687,6 +1687,6 @@ public abstract class ErrorMessages {
                     "The sys.prefix must be a str, not '%p' when the `IsolateNativeModules' option is used, because it is the base path for searching the relocated C API. " +
                                     "Refer to https://www.graalvm.org/latest/reference-manual/python/Native-Extensions for details on native module isolation.");
     public static final TruffleString SYS_PREFIX_MUST_POINT_TO_A_VENV_FOR_CAPI_ISOLATION = tsLiteral(
-                    "The sys.prefix must point to a venv, not be identical to sys.base_prefix when the `IsolateNativeModules' option is used, because it is the base path for searching and creating the relocated C API and extension modules. " +
+                    "The sys.prefix must point to a writable venv folder or the system default temporary directory needs to be writable when the `IsolateNativeModules' option is used, because it is the base path for searching and creating the relocated C API and extension modules. " +
                                     "Refer to https://www.graalvm.org/latest/reference-manual/python/Native-Extensions for details on native module isolation.");
 }