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 "nsExceptionHandler.h"
  11 #include "nsDebug.h"
  12 #include "nsString.h"
  13 #include "nsTArray.h"
  14
  15 #include "mozilla/X11Util.h"
  16 #include <X11/Xlib.h>
  17
  18 #define BUFSIZE 2048  // What Xlib uses with XGetErrorDatabaseText
  19
  20 struct XExtension {
  21   nsCString name;
  22   int major_opcode;
  23
  24   XExtension(const char* aName, int aCode) : name(aName), major_opcode(aCode) {}
  25 };
  26
  27 static nsTArray<XExtension> sXExtensions;
  28
  29 // man XSetErrorHandler says "the error handler should not call any
  30 // functions (directly or indirectly) on the display that will generate
  31 // protocol requests or that will look for input events" so we query the
  32 // extension list early to avoid problems.
  33 static void QueryXExtensions(Display* aDisplay) {
  34   if (!sXExtensions.IsEmpty() || !aDisplay) {
  35     return;
  36   }
  37   int nExts = 0;
  38   char** extNames = XListExtensions(aDisplay, &nExts);
  39   if (!extNames) {
  40     return;
  41   }
  42   for (int i = 0; i < nExts; ++i) {
  43     int major_opcode, first_event, first_error;
  44     if (XQueryExtension(aDisplay, extNames[i], &major_opcode, &first_event,
  45                         &first_error)) {
  46       sXExtensions.EmplaceBack(extNames[i], major_opcode);
  47     }
  48   }
  49   XFreeExtensionList(extNames);
  50 }
  51
  52 extern "C" {
  53 int X11Error(Display* display, XErrorEvent* event) {
  54 #ifdef DEBUG
  55   // Get an indication of how long ago the request that caused the error was
  56   // made.
  57   unsigned long age = NextRequest(display) - event->serial;
  58 #endif
  59
  60   // Get a string to represent the request that caused the error.
  61   nsAutoCString message;
  62   if (event->request_code < 128) {
  63     // Core protocol request
  64     message.AppendInt(event->request_code);
  65   } else {
  66     // Extension request
  67     for (XExtension& ext : sXExtensions) {
  68       if (ext.major_opcode == event->request_code) {
  69         message.Append(ext.name);
  70         message.Append('.');
  71         message.AppendInt(event->minor_code);
  72         break;
  73       }
  74     }
  75   }
  76
  77   char buffer[BUFSIZE];
  78   if (message.IsEmpty()) {
  79     buffer[0] = '\0';
  80   } else {
  81     XGetErrorDatabaseText(display, "XRequest", message.get(), "", buffer,
  82                           sizeof(buffer));
  83   }
  84
  85   nsAutoCString notes;
  86   if (buffer[0]) {
  87     notes.Append(buffer);
  88   } else {
  89     notes.AppendLiteral("Request ");
  90     notes.AppendInt(event->request_code);
  91     notes.Append('.');
  92     notes.AppendInt(event->minor_code);
  93   }
  94
  95   notes.AppendLiteral(": ");
  96
  97   // Get a string to describe the error.
  98   XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
  99   notes.Append(buffer);
 100
 101 #ifdef DEBUG
 102   // For requests where Xlib gets the reply synchronously, |age| will be 1
 103   // and the stack will include the function making the request.  For
 104   // asynchronous requests, the current stack will often be unrelated to the
 105   // point of making the request, even if |age| is 1, but sometimes this may
 106   // help us count back to the point of the request.  With XSynchronize on,
 107   // the stack will include the function making the request, even though
 108   // |age| will be 2 for asynchronous requests because XSynchronize is
 109   // implemented by an empty request from an XSync, which has not yet been
 110   // processed.
 111   if (age > 1) {
 112     // XSynchronize returns the previous "after function".  If a second
 113     // XSynchronize call returns the same function after an enable call then
 114     // synchronization must have already been enabled.
 115     if (XSynchronize(display, X11True) == XSynchronize(display, X11False)) {
 116       notes.AppendLiteral("; sync");
 117     } else {
 118       notes.AppendLiteral("; ");
 119       notes.AppendInt(uint32_t(age));
 120       notes.AppendLiteral(" requests ago");
 121     }
 122   }
 123
 124   // The resource id is unlikely to be useful in a crash report without
 125   // context of other ids, but add it to the debug console output.
 126   notes.AppendLiteral("; id=0x");
 127   notes.AppendInt(uint32_t(event->resourceid), 16);
 128 #  ifdef MOZ_X11
 129   // Actually, for requests where Xlib gets the reply synchronously,
 130   // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
 131   // which requests get a synchronous reply.
 132   if (!PR_GetEnv("MOZ_X_SYNC")) {
 133     notes.AppendLiteral(
 134         "\nRe-running with MOZ_X_SYNC=1 in the environment may give a more "
 135         "helpful backtrace.");
 136   }
 137 #  endif
 138 #endif
 139
 140   NS_WARNING(notes.get());
 141   return 0;
 142 }
 143 }
 144
 145 void InstallX11ErrorHandler() {
 146   XSetErrorHandler(X11Error);
 147
 148   if (Display* display = mozilla::DefaultXDisplay()) {
 149     QueryXExtensions(display);
 150     if (PR_GetEnv("MOZ_X_SYNC")) {
 151       XSynchronize(display, X11True);
 152     }
 153   }
 154 }
 155
 156 void CleanupX11ErrorHandler() { sXExtensions.Clear(); }