8269223: -Xcheck:jni WARNINGs working with fonts on Linux

src/java.desktop/share/native/libfontmanager/freetypeScaler.c

@@ -46,6 +46,12 @@
 
 #include "fontscaler.h"
 
+#define CHECK_EXCEPTION(env)            \
+    if ((*(env))->ExceptionCheck(env)) { \
+        (*(env))->ExceptionDescribe(env);\
+        (*(env))->ExceptionClear(env);   \
+    }
+
 #define  ftFixed1  (FT_Fixed) (1 << 16)
 #define  FloatToFTFixed(f) (FT_Fixed)((f) * (float)(ftFixed1))
 #define  FTFixedToFloat(x) ((x) / (float)(ftFixed1))
@@ -137,6 +143,8 @@ static void invalidateJavaScaler(JNIEnv *env,
                                  FTScalerInfo* scalerInfo) {
     freeNativeResources(env, scalerInfo);
     (*env)->CallVoidMethod(env, scaler, invalidateScalerMID);
+    // NB: Exceptions must not be cleared (and therefore no JNI calls performed) after calling this method
+    //     because it intentionally leaves an exception pending.
 }
 
 /******************* I/O handlers ***************************/
@@ -187,6 +195,8 @@ static unsigned long ReadTTFontFileFunc(FT_Stream stream,
                                           scalerInfo->font2D,
                                           sunFontIDs.ttReadBlockMID,
                                           bBuffer, offset, numBytes);
+            // This is a callback, we are not returning immediately to Java and better report exceptions now
+            CHECK_EXCEPTION(env);
             if (bread < 0) {
                 return 0;
             } else {
@@ -206,7 +216,9 @@ static unsigned long ReadTTFontFileFunc(FT_Stream stream,
             (*env)->CallObjectMethod(env, scalerInfo->font2D,
                                      sunFontIDs.ttReadBytesMID,
                                      offset, numBytes);
-            /* If there's an OutofMemoryError then byteArray will be null */
+            // This is a callback, we are not returning immediately to Java and better report exceptions now
+            CHECK_EXCEPTION(env);
+            /* If there's an OutOfMemoryError then byteArray will be null */
             if (byteArray == NULL) {
                 return 0;
             } else {
@@ -239,6 +251,8 @@ static unsigned long ReadTTFontFileFunc(FT_Stream stream,
                                       sunFontIDs.ttReadBlockMID,
                                       bBuffer, offset,
                                       scalerInfo->fontDataLength);
+        // This is a callback, we are not returning immediately to Java and better report exceptions now
+        CHECK_EXCEPTION(env);
         if (bread <= 0) {
             return 0;
         } else if ((unsigned long)bread < numBytes) {

test/jdk/java/awt/font/JNICheck/FreeTypeScalerJNICheck.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, JetBrains s.r.o.. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8269223
+ * @summary Verifies that -Xcheck:jni issues no warnings from freetypeScaler.c
+ * @requires os.family == "linux"
+ * @library /test/lib
+ * @run main FreeTypeScalerJNICheck
+ */
+import javax.swing.*;
+import java.awt.*;
+import java.awt.geom.Rectangle2D;
+import java.awt.image.*;
+import java.io.*;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+
+public class FreeTypeScalerJNICheck {
+    public static void main(String[] args) throws Exception {
+        if (args.length > 0 && args[0].equals("runtest")) {
+            runTest();
+        } else {
+            ProcessBuilder pb = ProcessTools.createTestJvm("-Xcheck:jni", FreeTypeScalerJNICheck.class.getName(), "runtest");
+            OutputAnalyzer oa = ProcessTools.executeProcess(pb);
+            oa.shouldContain("Done").shouldNotContain("WARNING").shouldHaveExitValue(0);
+        }
+    }
+
+    public static void runTest() {
+        String families[] = GraphicsEnvironment.getLocalGraphicsEnvironment().getAvailableFontFamilyNames();
+        JFrame frame = new JFrame("test");
+        BufferedImage bi = new BufferedImage(1, 1, BufferedImage.TYPE_INT_RGB);
+        Graphics2D g2d = bi.createGraphics();
+
+        for (String ff : families)
+        {
+            Font font = Font.decode(ff);
+            Rectangle2D bounds = font.getStringBounds("test", g2d.getFontRenderContext());
+            FontMetrics metrics = frame.getFontMetrics(font);
+            System.out.println(bounds.getHeight() + metrics.getHeight()); // use bounds and metrics
+        }
+
+        System.out.println("Done");
+    }
+}
+