Refactor nativeGetStackTrace to call backtrace_symbols only once when producing call stacks, rather than for every StackTraceElement.

jre_emul/Classes/JavaThrowable.m

@@ -84,34 +84,41 @@ static bool ShouldFilterStackElement(JavaLangStackTraceElement *element) {
   return false;
 }
 
-static void ProcessRawStack(RawStack *rawStack, NSMutableArray *frames, bool applyFilter) {
-  for (unsigned i = 0; i < rawStack->count_; i++) {
-    JavaLangStackTraceElement *element =
-        [[JavaLangStackTraceElement alloc] initWithLong:(jlong)rawStack->frames_[i]];
-    if (!applyFilter || !ShouldFilterStackElement(element)) {
-      [frames addObject:element];
-    }
-    [element release];
-  }
-}
-
 jarray Java_java_lang_Throwable_nativeGetStackTrace(
     JNIEnv *_env_, jclass _cls_, jobject stackState) {
   RawStack *rawStack = stackState;
   NSMutableArray *frames = [NSMutableArray array];
-  if (rawStack) {
-    ProcessRawStack(rawStack, frames, true);
-    JavaLangStackTraceElement *element = [frames lastObject];
+  if (rawStack && rawStack->count_ > 0) {
+    char **stackSymbols = backtrace_symbols(rawStack->frames_, rawStack->count_);
+    NSStringEncoding encoding = [NSString defaultCStringEncoding];
+
+    for (unsigned i = 0; i < rawStack->count_; i++) {
+      NSString *symbolStr = [NSString stringWithCString:stackSymbols[i] encoding:encoding];
+      JavaLangStackTraceElement *element = 
+          JavaLangStackTraceElement_createFromSymbolWithLong_withNSString_((jlong)rawStack->frames_[i], symbolStr);
+
+      if (!ShouldFilterStackElement(element)) {
+        [frames addObject:element];
+      }
+    }
+
     // Remove initial Method.invoke(), so app's main method is last.
+    JavaLangStackTraceElement *element = [frames lastObject];
     if ([[element getClassName] isEqualToString:@"JavaLangReflectMethod"] &&
         [[element getMethodName] isEqualToString:@"invoke"]) {
       [frames removeLastObject];
     }
     // If symbols were removed, the stack trace will be empty at this point.
     // In order to help with debugging, return the raw stack trace.
     if ([frames count] == 0) {
-      ProcessRawStack(rawStack, frames, false);
+      for (unsigned i = 0; i < rawStack->count_; i++) {
+        NSString *symbolStr = [NSString stringWithCString:stackSymbols[i] encoding:encoding];
+        JavaLangStackTraceElement *element = 
+            JavaLangStackTraceElement_createFromSymbolWithLong_withNSString_((jlong)rawStack->frames_[i], symbolStr);
+        [frames addObject:element];
+      }
     }
+    free(stackSymbols);
   }
   return [IOSObjectArray arrayWithNSArray:frames type:JavaLangStackTraceElement_class_()];
 }

jre_emul/Classes/java/lang/StackTraceElement.java

@@ -78,6 +78,13 @@ public StackTraceElement(String className, String methodName, String fileName, i
     this.address = address;
   }
 
+  public static native StackTraceElement createFromSymbol(long address, String symbol) /*-[
+    JavaLangStackTraceElement *element = [[JavaLangStackTraceElement alloc] initWithLong:address];
+    NSStringEncoding encoding = [NSString defaultCStringEncoding];
+    PopulateElementFromSymbol(element, [symbol UTF8String], encoding);
+    return AUTORELEASE(element);
+  ]-*/;
+
   @Override
   public String toString() {
     initializeFromAddress();
@@ -239,21 +246,10 @@ static void DemangleSwiftMethod(
   }
   ]-*/
 
-  /**
-   * Implements lazy loading of symbol information from application.
-   */
-  private native void initializeFromAddress() /*-[
-    if (self->address_ == 0L     // Is there an address to initialze from?
-        || self->hexAddress_) {  // Already initialized?
-      return;
-    }
-    void *shortStack[1];
-    shortStack[0] = (void *)self->address_;
-    char **stackSymbol = backtrace_symbols(shortStack, 1);
-    NSStringEncoding encoding = [NSString defaultCStringEncoding];
-
-    // Extract hexAddress.
-    char *start = strstr(*stackSymbol, "0x");  // Skip text before address.
+  /*-[
+  static void PopulateElementFromSymbol(JavaLangStackTraceElement *self, const char *stackSymbol, NSStringEncoding encoding) {
+    char *symbolCopy = strdup(stackSymbol);
+    char *start = strstr(symbolCopy, "0x");
     char *addressEnd = strstr(start, " ");
     char *hex = strndup(start, addressEnd - start);
     self->hexAddress_ = [[NSString alloc] initWithCString:hex encoding:encoding];
@@ -325,6 +321,21 @@ private native void initializeFromAddress() /*-[
     if ([self->methodName_ isEqual:JavaLangStackTraceElement_UNKNOWN]) {
       self->methodName_ = JavaLangStackTraceElement_STRIPPED;
     }
+    free(symbolCopy);
+  }
+  ]-*/
+
+  /** Implements lazy loading of symbol information from application. */
+  private native void initializeFromAddress() /*-[
+    if (self->address_ == 0L     // Is there an address to initialze from?
+        || self->hexAddress_) {  // Already initialized?
+      return;
+    }
+    void *shortStack[1];
+    shortStack[0] = (void *)self->address_;
+    char **stackSymbol = backtrace_symbols(shortStack, 1);
+    NSStringEncoding encoding = [NSString defaultCStringEncoding];
+    PopulateElementFromSymbol(self, *stackSymbol, encoding);
     free(stackSymbol);
   ]-*/;
 }

jre_emul/misc_tests/com/google/j2objc/ThrowableTest.java

@@ -18,6 +18,7 @@
 
 import com.google.j2objc.util.ReflectionUtil;
 import java.io.ByteArrayOutputStream;
+import java.lang.reflect.Method;
 import java.io.PrintStream;
 import java.io.PrintWriter;
 import java.io.StringWriter;
@@ -123,6 +124,29 @@ public void testThrowableToStringFormat() {
     assertTrue(ReflectionUtil.matchClassNamePrefix(new Throwable("oops").toString(), expected));
   }
 
+  public void testSymbolParsing() {
+    // A typical Objective-C symbol string generated by J2ObjC
+    String symbol =
+        "0   MyApp                               0x0000000100000f14 [ComGoogleJ2objcThrowableTest"
+            + " testSymbolParsing] + 0";
+    long address = 0x100000f14L;
+
+    // Create a StackTraceElement from the symbol.
+    StackTraceElement element = StackTraceElement.createFromSymbol(address, symbol);
+    assertNotNull(element);
+    assertEquals("com.google.j2objc.ThrowableTest", element.getClassName());
+    assertEquals("testSymbolParsing", element.getMethodName());
+
+    // Create an element via the public constructor and verify equivalence.
+    StackTraceElement expectedElement =
+        new StackTraceElement("com.google.j2objc.ThrowableTest", "testSymbolParsing", null, -1);
+
+    assertEquals(expectedElement, element);
+    assertEquals(expectedElement.toString(), element.toString());
+    assertEquals(expectedElement.getClassName(), element.getClassName());
+    assertEquals(expectedElement.getMethodName(), element.getMethodName());
+  }
+
   public void testNSExceptionDescriptionUnchanged() {
     assertEquals(NSEXCEPTION_MESSAGE, getNSExceptionDescription());
   }