Default location of the symbols is $ANDROID_PRODUCT_OUT/symbols. Setting the env variable ANDROID_SYMBOLS allows you to override this location so that DDMS goes look for the symbol in a different location when resolving native heap addresses.
Using the Eclipse projects for ddmuilib. ddmuilib requires SWT to compile. SWT is available in the depot under prebuild/<platform>/swt Because the build path cannot contain relative path that are not inside the project directory, the .classpath file references a user library called ANDROID_SWT. In order to compile the project, make a user library called ANDROID_SWT containing the jar available at prebuild/<platform>/swt.