7016187: javac -h could generate conflict .h for inner class and cl…

…ass name with '_'

Reviewed-by: vromero

src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/JNIWriter.java

@@ -29,6 +29,7 @@
 import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 
 import javax.tools.FileObject;
@@ -84,6 +85,12 @@ public class JNIWriter {
      */
     private boolean checkAll;
 
+    /**
+     * Mapping from output file name to class name, for all classes we've written.
+     * This is used to detect when two classes generate the same output file.
+     */
+    private final HashMap<String, String> filesWritten = new HashMap<>();
+
     /**
      * If true, class files will be written in module-specific subdirectories
      * of the NATIVE_HEADER_OUTPUT location.
@@ -183,9 +190,14 @@ public FileObject write(ClassSymbol c) throws IOException {
         } else {
             outLocn = StandardLocation.NATIVE_HEADER_OUTPUT;
         }
-        FileObject outFile
-            = fileManager.getFileForOutput(outLocn,
-                "", className.replaceAll("[.$]", "_") + ".h", null);
+        String fileName = className.replaceAll("[.$]", "_") + ".h";
+        String prevName = filesWritten.put(fileName, className);
+        if (prevName != null) {
+            throw new IOException(String.format(
+              "native header file collision between %s and %s (both generate %s)",
+              prevName, className, fileName));
+        }
+        FileObject outFile = fileManager.getFileForOutput(outLocn, "", fileName, null);
         PrintWriter out = new PrintWriter(outFile.openWriter());
         try {
             write(out, c);

test/langtools/tools/javac/nativeHeaders/NativeHeaderTest.java

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 7150368 8003412 8000407
+ * @bug 7150368 8003412 8000407 7016187
  * @summary javac should include basic ability to generate native headers
  * @modules jdk.compiler/com.sun.tools.javac.api
  *          jdk.compiler/com.sun.tools.javac.file
@@ -149,6 +149,32 @@ void annoNestedClassTest(RunKind rk, GenKind gk) throws Exception {
         test(rk, gk, files, expect);
     }
 
+    @Test
+    void conflictTest(RunKind rk, GenKind gk) throws Exception {
+
+        // These two classes will generate the same header file "Foo_Bar.h"
+        List<File> files = new ArrayList<File>();
+        files.add(createFile("p/Foo.java", """
+            public class Foo {
+                public static class Bar {
+                    public static native void method1();
+                }
+            }
+        """));
+        files.add(createFile("p/Foo_Bar.java", """
+            public class Foo_Bar {
+                public static native void method2();
+            }
+        """));
+
+        try {
+            test(rk, gk, files, null);
+            throw new AssertionError("expected failure");
+        } catch (Exception e) {
+            // expected
+        }
+    }
+
     /**
      * The worker method for each test case.
      * Compile the files and verify that exactly the expected set of header files