<set-property name="compiler.stackMode" value="emulated" />
<set-configuration-property name="compiler.emulatedStack.recordLineNumbers"
    value="true" />

com.google.gwt.core.client.JavaScriptException: (TypeError) : Cannot call method 'pp' of null
    Unknown.aT(Unknown Source:174)
    Unknown.AVa(Unknown Source:501)
    Unknown.YF(Unknown Source:29)
    Unknown.Lqb(Unknown Source:138)
    ...

// Create the deobfuscator
String dir = getSymbolMapsDirPath();
StackTraceDeobfuscator deobfuscator = new StackTraceDeobfuscator(dir);

// request is the HttpServletRequest
String strongName = request.getHeader(RpcRequestBuilder.STRONG_NAME_HEADER);

// Deobfuscate the stack trace
exception.setStackTrace(
    deobfuscator.deobfuscateStackTrace(exception.getStackTrace(), strongName));

// Log the exception
logger.severe("Uncaught GWT exception", exception);

import com.google.gwt.core.server.StackTraceDeobfuscator;
import com.google.gwt.user.client.rpc.RpcRequestBuilder;

String path = getServletConfig().getServletContext().getRealPath("/WEB-INF/deploy/<your module name>/symbolMaps/");
StackTraceDeobfuscator deobfuscator = StackTraceDeobfuscator.fromFileSystem(path);
String strongName = getThreadLocalRequest().getHeader(RpcRequestBuilder.STRONG_NAME_HEADER);

// Do the magic
deobfuscator.deobfuscateStackTrace(exception, strongName);

// Log it
logger.severe("Uncaught GWT exception", exception);