1 files changed, 156 insertions, 0 deletions
diff --git a/toolkit/xre/nsX11ErrorHandler.cpp b/toolkit/xre/nsX11ErrorHandler.cpp
new file mode 100644
index 0000000000..77f71db8f9
--- /dev/null
+++ b/toolkit/xre/nsX11ErrorHandler.cpp
@@ -0,0 +1,156 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsX11ErrorHandler.h"
+
+#include "prenv.h"
+#include "nsXULAppAPI.h"
+#include "nsExceptionHandler.h"
+#include "nsDebug.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+#include "mozilla/X11Util.h"
+#include <X11/Xlib.h>
+
+#define BUFSIZE 2048  // What Xlib uses with XGetErrorDatabaseText
+
+struct XExtension {
+  nsCString name;
+  int major_opcode;
+
+  XExtension(const char* aName, int aCode) : name(aName), major_opcode(aCode) {}
+};
+
+static nsTArray<XExtension> sXExtensions;
+
+// man XSetErrorHandler says "the error handler should not call any
+// functions (directly or indirectly) on the display that will generate
+// protocol requests or that will look for input events" so we query the
+// extension list early to avoid problems.
+static void QueryXExtensions(Display* aDisplay) {
+  if (!sXExtensions.IsEmpty() || !aDisplay) {
+    return;
+  }
+  int nExts = 0;
+  char** extNames = XListExtensions(aDisplay, &nExts);
+  if (!extNames) {
+    return;
+  }
+  for (int i = 0; i < nExts; ++i) {
+    int major_opcode, first_event, first_error;
+    if (XQueryExtension(aDisplay, extNames[i], &major_opcode, &first_event,
+                        &first_error)) {
+      sXExtensions.EmplaceBack(extNames[i], major_opcode);
+    }
+  }
+  XFreeExtensionList(extNames);
+}
+
+extern "C" {
+int X11Error(Display* display, XErrorEvent* event) {
+#ifdef DEBUG
+  // Get an indication of how long ago the request that caused the error was
+  // made.
+  unsigned long age = NextRequest(display) - event->serial;
+#endif
+
+  // Get a string to represent the request that caused the error.
+  nsAutoCString message;
+  if (event->request_code < 128) {
+    // Core protocol request
+    message.AppendInt(event->request_code);
+  } else {
+    // Extension request
+    for (XExtension& ext : sXExtensions) {
+      if (ext.major_opcode == event->request_code) {
+        message.Append(ext.name);
+        message.Append('.');
+        message.AppendInt(event->minor_code);
+        break;
+      }
+    }
+  }
+
+  char buffer[BUFSIZE];
+  if (message.IsEmpty()) {
+    buffer[0] = '\0';
+  } else {
+    XGetErrorDatabaseText(display, "XRequest", message.get(), "", buffer,
+                          sizeof(buffer));
+  }
+
+  nsAutoCString notes;
+  if (buffer[0]) {
+    notes.Append(buffer);
+  } else {
+    notes.AppendLiteral("Request ");
+    notes.AppendInt(event->request_code);
+    notes.Append('.');
+    notes.AppendInt(event->minor_code);
+  }
+
+  notes.AppendLiteral(": ");
+
+  // Get a string to describe the error.
+  XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
+  notes.Append(buffer);
+
+#ifdef DEBUG
+  // For requests where Xlib gets the reply synchronously, |age| will be 1
+  // and the stack will include the function making the request.  For
+  // asynchronous requests, the current stack will often be unrelated to the
+  // point of making the request, even if |age| is 1, but sometimes this may
+  // help us count back to the point of the request.  With XSynchronize on,
+  // the stack will include the function making the request, even though
+  // |age| will be 2 for asynchronous requests because XSynchronize is
+  // implemented by an empty request from an XSync, which has not yet been
+  // processed.
+  if (age > 1) {
+    // XSynchronize returns the previous "after function".  If a second
+    // XSynchronize call returns the same function after an enable call then
+    // synchronization must have already been enabled.
+    if (XSynchronize(display, X11True) == XSynchronize(display, X11False)) {
+      notes.AppendLiteral("; sync");
+    } else {
+      notes.AppendLiteral("; ");
+      notes.AppendInt(uint32_t(age));
+      notes.AppendLiteral(" requests ago");
+    }
+  }
+
+  // The resource id is unlikely to be useful in a crash report without
+  // context of other ids, but add it to the debug console output.
+  notes.AppendLiteral("; id=0x");
+  notes.AppendInt(uint32_t(event->resourceid), 16);
+#  ifdef MOZ_X11
+  // Actually, for requests where Xlib gets the reply synchronously,
+  // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
+  // which requests get a synchronous reply.
+  if (!PR_GetEnv("MOZ_X_SYNC")) {
+    notes.AppendLiteral(
+        "\nRe-running with MOZ_X_SYNC=1 in the environment may give a more "
+        "helpful backtrace.");
+  }
+#  endif
+#endif
+
+  NS_WARNING(notes.get());
+  return 0;
+}
+}
+
+void InstallX11ErrorHandler() {
+  XSetErrorHandler(X11Error);
+
+  if (Display* display = mozilla::DefaultXDisplay()) {
+    QueryXExtensions(display);
+    if (PR_GetEnv("MOZ_X_SYNC")) {
+      XSynchronize(display, X11True);
+    }
+  }
+}
+
+void CleanupX11ErrorHandler() { sXExtensions.Clear(); }