toolkit/xre/nsX11ErrorHandler.cpp

   1 /* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "nsX11ErrorHandler.h"
   7
   8 #include "prenv.h"
   9 #include "nsXULAppAPI.h"
  10 #include "nsDebug.h"
  11
  12 #include "mozilla/X11Util.h"
  13 #include <X11/Xlib.h>
  14
  15 #define BUFSIZE 2048 // What Xlib uses with XGetErrorDatabaseText
  16
  17 extern "C" {
  18 int
  19 X11Error(Display *display, XErrorEvent *event) {
  20   // Get an indication of how long ago the request that caused the error was
  21   // made.
  22   unsigned long age = NextRequest(display) - event->serial;
  23
  24   // Get a string to represent the request that caused the error.
  25   nsAutoCString message;
  26   if (event->request_code < 128) {
  27     // Core protocol request
  28     message.AppendInt(event->request_code);
  29   } else {
  30     // Extension request
  31
  32     // man XSetErrorHandler says "the error handler should not call any
  33     // functions (directly or indirectly) on the display that will generate
  34     // protocol requests or that will look for input events" so we use another
  35     // temporary Display to request extension information.  This assumes on
  36     // the DISPLAY environment variable has been set and matches what was used
  37     // to open |display|.
  38     Display *tmpDisplay = XOpenDisplay(nullptr);
  39     if (tmpDisplay) {
  40       int nExts;
  41       char** extNames = XListExtensions(tmpDisplay, &nExts);
  42       int first_error;
  43       if (extNames) {
  44         for (int i = 0; i < nExts; ++i) {
  45           int major_opcode, first_event;
  46           if (XQueryExtension(tmpDisplay, extNames[i],
  47                               &major_opcode, &first_event, &first_error)
  48               && major_opcode == event->request_code) {
  49             message.Append(extNames[i]);
  50             message.Append('.');
  51             message.AppendInt(event->minor_code);
  52             break;
  53           }
  54         }
  55
  56         XFreeExtensionList(extNames);
  57       }
  58       XCloseDisplay(tmpDisplay);
  59
  60 #if (MOZ_WIDGET_GTK == 2)
  61       // GDK2 calls XCloseDevice the devices that it opened on startup, but
  62       // the XI protocol no longer ensures that the devices will still exist.
  63       // If they have been removed, then a BadDevice error results.  Ignore
  64       // this error.
  65       if (message.EqualsLiteral("XInputExtension.4") &&
  66           event->error_code == first_error + 0) {
  67         return 0;
  68       }
  69 #endif
  70     }
  71   }
  72
  73   char buffer[BUFSIZE];
  74   if (message.IsEmpty()) {
  75     buffer[0] = '\0';
  76   } else {
  77     XGetErrorDatabaseText(display, "XRequest", message.get(), "",
  78                           buffer, sizeof(buffer));
  79   }
  80
  81   nsAutoCString notes;
  82   if (buffer[0]) {
  83     notes.Append(buffer);
  84   } else {
  85     notes.AppendLiteral("Request ");
  86     notes.AppendInt(event->request_code);
  87     notes.Append('.');
  88     notes.AppendInt(event->minor_code);
  89   }
  90
  91   notes.AppendLiteral(": ");
  92
  93   // Get a string to describe the error.
  94   XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
  95   notes.Append(buffer);
  96
  97   // For requests where Xlib gets the reply synchronously, |age| will be 1
  98   // and the stack will include the function making the request.  For
  99   // asynchronous requests, the current stack will often be unrelated to the
 100   // point of making the request, even if |age| is 1, but sometimes this may
 101   // help us count back to the point of the request.  With XSynchronize on,
 102   // the stack will include the function making the request, even though
 103   // |age| will be 2 for asynchronous requests because XSynchronize is
 104   // implemented by an empty request from an XSync, which has not yet been
 105   // processed.
 106   if (age > 1) {
 107     // XSynchronize returns the previous "after function".  If a second
 108     // XSynchronize call returns the same function after an enable call then
 109     // synchronization must have already been enabled.
 110     if (XSynchronize(display, True) == XSynchronize(display, False)) {
 111       notes.AppendLiteral("; sync");
 112     } else {
 113       notes.AppendLiteral("; ");
 114       notes.AppendInt(uint32_t(age));
 115       notes.AppendLiteral(" requests ago");
 116     }
 117   }
 118
 119 #ifdef DEBUG
 120   // The resource id is unlikely to be useful in a crash report without
 121   // context of other ids, but add it to the debug console output.
 122   notes.AppendLiteral("; id=0x");
 123   notes.AppendInt(uint32_t(event->resourceid), 16);
 124 #ifdef MOZ_X11
 125   // Actually, for requests where Xlib gets the reply synchronously,
 126   // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
 127   // which requests get a synchronous reply.
 128   if (!PR_GetEnv("MOZ_X_SYNC")) {
 129     notes.AppendLiteral("\nRe-running with MOZ_X_SYNC=1 in the environment may give a more helpful backtrace.");
 130   }
 131 #endif
 132 #endif
 133
 134 #ifdef MOZ_WIDGET_QT
 135   // We should not abort here if MOZ_X_SYNC is not set
 136   // until http://bugreports.qt.nokia.com/browse/QTBUG-4042
 137   // not fixed, just print error value
 138   if (!PR_GetEnv("MOZ_X_SYNC")) {
 139     fprintf(stderr, "XError: %s\n", notes.get());
 140     return 0; // temporary workaround for bug 161472
 141   }
 142 #endif
 143
 144   NS_RUNTIMEABORT(notes.get());
 145   return 0; // not reached
 146 }
 147 }
 148
 149 #if (MOZ_WIDGET_GTK != 3)
 150 void
 151 InstallX11ErrorHandler()
 152 {
 153   XSetErrorHandler(X11Error);
 154
 155   Display *display = mozilla::DefaultXDisplay();
 156   NS_ASSERTION(display, "No X display");
 157   if (PR_GetEnv("MOZ_X_SYNC")) {
 158     XSynchronize(display, True);
 159   }
 160 }
 161 #endif