fix mkdtemp bug

com.oracle.truffle.r.native/fficall/src/jni/base_rffi.c

@@ -58,11 +58,15 @@ Java_com_oracle_truffle_r_runtime_ffi_jni_JNI_1Base_native_1setwd(JNIEnv *env, j
 
 JNIEXPORT jint JNICALL
 Java_com_oracle_truffle_r_runtime_ffi_jni_JNI_1Base_native_1mkdtemp(JNIEnv *env, jclass c, jbyteArray jtemplate) {
-    char *template = (*env)->GetPrimitiveArrayCritical(env, jtemplate, NULL);
+    char *template = (char*) (*env)->GetByteArrayElements(env, jtemplate, NULL);
     char *r = mkdtemp(template);
-    if (r == NULL) return 0;
-    (*env)->ReleasePrimitiveArrayCritical(env, jtemplate, template, 0);
-    return 1;
+    int rc = 1;
+    if (r == NULL) {
+    	// printf("mkdtemp errno: %d\n", errno);
+    	rc = 0;
+    }
+    (*env)->ReleaseByteArrayElements(env, jtemplate, (jbyte*) template, rc == 1 ? 0 : JNI_ABORT);
+    return rc;
 }
 
 JNIEXPORT jint JNICALL

com.oracle.truffle.r.runtime.ffi/src/com/oracle/truffle/r/runtime/ffi/jni/JNI_Base.java

@@ -72,12 +72,19 @@ public class JNI_Base implements BaseRFFI {
 
     @Override
     public String mkdtemp(String template) {
+        /*
+         * Not only must the (C) string end in XXXXXX it must also be null-terminated. Since it is
+         * modified by mkdtemp we must make a copy.
+         */
         byte[] bytes = template.getBytes();
-        long result = native_mkdtemp(bytes);
+        byte[] ztbytes = new byte[bytes.length + 1];
+        System.arraycopy(bytes, 0, ztbytes, 0, bytes.length);
+        ztbytes[bytes.length] = 0;
+        long result = native_mkdtemp(ztbytes);
         if (result == 0) {
             return null;
         } else {
-            return new String(bytes);
+            return new String(ztbytes, 0, bytes.length);
         }
     }