Improve "waiting on"/"waiting to lock" SIGQUIT dump info.

In particular, when we're waiting on a Class, say which class:

  I(16573)   - waiting on <0xf5ed54f8> (java.lang.Class<java.lang.ref.ReferenceQueue>)

versus:

  I(16573)   - waiting on <0xf5feda38> (a java.util.LinkedList)

Bug: http://code.google.com/p/android/issues/detail?id=17349
Change-Id: I844d02c008b1499adb02995ff3da25ba8cad0e0a

1 files changed, 55 insertions, 0 deletions

diff --git a/vm/Misc.cpp b/vm/Misc.cpp
index 627c4e2ec..3b1179e44 100644
--- a/vm/Misc.cpp
+++ b/vm/Misc.cpp
@@ -715,3 +715,58 @@ const char* dvmPathToAbsolutePortion(const char* path) {
 
     return NULL;
 }
+
+// From RE2.
+static void StringAppendV(std::string* dst, const char* format, va_list ap) {
+    // First try with a small fixed size buffer
+    char space[1024];
+
+    // It's possible for methods that use a va_list to invalidate
+    // the data in it upon use.  The fix is to make a copy
+    // of the structure before using it and use that copy instead.
+    va_list backup_ap;
+    va_copy(backup_ap, ap);
+    int result = vsnprintf(space, sizeof(space), format, backup_ap);
+    va_end(backup_ap);
+
+    if ((result >= 0) && ((size_t) result < sizeof(space))) {
+        // It fit
+        dst->append(space, result);
+        return;
+    }
+
+    // Repeatedly increase buffer size until it fits
+    int length = sizeof(space);
+    while (true) {
+        if (result < 0) {
+            // Older behavior: just try doubling the buffer size
+            length *= 2;
+        } else {
+            // We need exactly "result+1" characters
+            length = result+1;
+        }
+        char* buf = new char[length];
+
+        // Restore the va_list before we use it again
+        va_copy(backup_ap, ap);
+        result = vsnprintf(buf, length, format, backup_ap);
+        va_end(backup_ap);
+
+        if ((result >= 0) && (result < length)) {
+            // It fit
+            dst->append(buf, result);
+            delete[] buf;
+            return;
+        }
+        delete[] buf;
+    }
+}
+
+std::string dvmStringPrintf(const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    std::string result;
+    StringAppendV(&result, fmt, ap);
+    va_end(ap);
+    return result;
+}