[Emacs-diffs] trunk r115351: Improve reporting of fatal exception on MS-Windows, to aid debugging #15994.

[Eli Zaretskii]

------------------------------------------------------------
revno: 115351
revision-id: address@hidden
parent: address@hidden
fixes bug: http://debbugs.gnu.org/15994
committer: Eli Zaretskii <address@hidden>
branch nick: trunk
timestamp: Mon 2013-12-02 19:28:17 +0200
message:
  Improve reporting of fatal exception on MS-Windows, to aid debugging #15994.
  
   src/w32fns.c (my_exception_handler): New function.
   (globals_of_w32fns): Set it up as the unhandled exception
   handler.  Initialize exception code and address to zeros.
   (emacs_abort): If the exception code and address are available,
   print them at the beginning of the backtrace.  Fix the format of
   printing addresses (was producing 0x0x12345678 on XP).
modified:
  src/ChangeLog                  changelog-20091113204419-o5vbwnq5f7feedwu-1438
  src/w32fns.c                   w32fns.c-20091113204419-o5vbwnq5f7feedwu-945

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2013-12-02 14:45:22 +0000
+++ b/src/ChangeLog     2013-12-02 17:28:17 +0000
@@ -1,3 +1,14 @@
+2013-12-02  Eli Zaretskii  <address@hidden>
+
+       Improve reporting of fatal exception on MS-Windows.
+       * w32fns.c (my_exception_handler): New function.
+       (globals_of_w32fns): Set it up as the unhandled exception
+       handler.  Initialize exception code and address to zeros.
+       (emacs_abort): If the exception code and address are available,
+       print them at the beginning of the backtrace.  Fix the format of
+       printing addresses (was producing 0x0x12345678 on XP).
+       (Bug#15994)
+
 2013-12-02  Helmut Eller  <address@hidden>
 
        * eval.c (Fbacktrace__locals): New function.

=== modified file 'src/w32fns.c'
--- a/src/w32fns.c      2013-12-01 22:33:13 +0000
+++ b/src/w32fns.c      2013-12-02 17:28:17 +0000
@@ -7969,61 +7969,35 @@
 #endif
 }
 
-
-/*
-       globals_of_w32fns is used to initialize those global variables that
-       must always be initialized on startup even when the global variable
-       initialized is non zero (see the function main in emacs.c).
-       globals_of_w32fns is called from syms_of_w32fns when the global
-       variable initialized is 0 and directly from main when initialized
-       is non zero.
- */
-void
-globals_of_w32fns (void)
+
+
+/* Crashing and reporting backtrace.  */
+
+#ifndef CYGWIN
+static LONG CALLBACK my_exception_handler (EXCEPTION_POINTERS *);
+static LPTOP_LEVEL_EXCEPTION_FILTER prev_exception_handler;
+#endif
+static DWORD except_code;
+static PVOID except_addr;
+
+#ifndef CYGWIN
+/* This handler records the exception code and the address where it
+   was triggered so that this info could be included in the backtrace.
+   Without that, the backtrace in some cases has no information
+   whatsoever about the offending code, and looks as if the top-level
+   exception handler in the MinGW startup code di the one that
+   crashed.  */
+static LONG CALLBACK
+my_exception_handler (EXCEPTION_POINTERS * exception_data)
 {
-  HMODULE user32_lib = GetModuleHandle ("user32.dll");
-  /*
-    TrackMouseEvent not available in all versions of Windows, so must load
-    it dynamically.  Do it once, here, instead of every time it is used.
-  */
-  track_mouse_event_fn = (TrackMouseEvent_Proc)
-    GetProcAddress (user32_lib, "TrackMouseEvent");
-
-  monitor_from_point_fn = (MonitorFromPoint_Proc)
-    GetProcAddress (user32_lib, "MonitorFromPoint");
-  get_monitor_info_fn = (GetMonitorInfo_Proc)
-    GetProcAddress (user32_lib, "GetMonitorInfoA");
-  monitor_from_window_fn = (MonitorFromWindow_Proc)
-    GetProcAddress (user32_lib, "MonitorFromWindow");
-  enum_display_monitors_fn = (EnumDisplayMonitors_Proc)
-    GetProcAddress (user32_lib, "EnumDisplayMonitors");
-
-  {
-    HMODULE imm32_lib = GetModuleHandle ("imm32.dll");
-    get_composition_string_fn = (ImmGetCompositionString_Proc)
-      GetProcAddress (imm32_lib, "ImmGetCompositionStringW");
-    get_ime_context_fn = (ImmGetContext_Proc)
-      GetProcAddress (imm32_lib, "ImmGetContext");
-    release_ime_context_fn = (ImmReleaseContext_Proc)
-      GetProcAddress (imm32_lib, "ImmReleaseContext");
-    set_ime_composition_window_fn = (ImmSetCompositionWindow_Proc)
-      GetProcAddress (imm32_lib, "ImmSetCompositionWindow");
-  }
-  DEFVAR_INT ("w32-ansi-code-page",
-             w32_ansi_code_page,
-             doc: /* The ANSI code page used by the system.  */);
-  w32_ansi_code_page = GetACP ();
-
-  if (os_subtype == OS_NT)
-    w32_unicode_gui = 1;
-  else
-    w32_unicode_gui = 0;
-
-  /* MessageBox does not work without this when linked to comctl32.dll 6.0.  */
-  InitCommonControls ();
-
-  syms_of_w32uniscribe ();
+  except_code = exception_data->ExceptionRecord->ExceptionCode;
+  except_addr = exception_data->ExceptionRecord->ExceptionAddress;
+
+  if (prev_exception_handler)
+    return prev_exception_handler (exception_data);
+  return EXCEPTION_EXECUTE_HANDLER;
 }
+#endif
 
 typedef USHORT (WINAPI * CaptureStackBackTrace_proc) (ULONG, ULONG, PVOID *,
                                                      PULONG);
@@ -8080,21 +8054,32 @@
 
        if (i)
          {
+           int errfile_fd = -1;
+           int j;
+           char buf[sizeof ("\r\nException  at this address:\r\n\r\n")
+                    + 2 * INT_BUFSIZE_BOUND (void *)];
 #ifdef CYGWIN
            int stderr_fd = 2;
 #else
            HANDLE errout = GetStdHandle (STD_ERROR_HANDLE);
            int stderr_fd = -1;
-#endif
-           int errfile_fd = -1;
-           int j;
 
-#ifndef CYGWIN
            if (errout && errout != INVALID_HANDLE_VALUE)
              stderr_fd = _open_osfhandle ((intptr_t)errout, O_APPEND | 
O_BINARY);
 #endif
+
+           /* We use %p, not 0x%p, as %p produces a leading "0x" on XP,
+              but not on Windows 7.  addr2line doesn't mind a missing
+              "0x", but will be confused by an extra one.  */
+           if (except_addr)
+             sprintf (buf, "\r\nException 0x%lx at this address:\r\n%p\r\n",
+                      except_code, except_addr);
            if (stderr_fd >= 0)
-             write (stderr_fd, "\r\nBacktrace:\r\n", 14);
+             {
+               if (except_addr)
+                 write (stderr_fd, buf, strlen (buf));
+               write (stderr_fd, "\r\nBacktrace:\r\n", 14);
+             }
 #ifdef CYGWIN
 #define _open open
 #endif
@@ -8102,17 +8087,17 @@
            if (errfile_fd >= 0)
              {
                lseek (errfile_fd, 0L, SEEK_END);
+               if (except_addr)
+                 write (errfile_fd, buf, strlen (buf));
                write (errfile_fd, "\r\nBacktrace:\r\n", 14);
              }
 
            for (j = 0; j < i; j++)
              {
-               char buf[INT_BUFSIZE_BOUND (void *)];
-
                /* stack[] gives the return addresses, whereas we want
                   the address of the call, so decrease each address
                   by approximate size of 1 CALL instruction.  */
-               sprintf (buf, "0x%p\r\n", (char *)stack[j] - sizeof(void *));
+               sprintf (buf, "%p\r\n", (char *)stack[j] - sizeof(void *));
                if (stderr_fd >= 0)
                  write (stderr_fd, buf, strlen (buf));
                if (errfile_fd >= 0)
@@ -8134,6 +8119,72 @@
     }
 }
 
+
+
+/* Initialization.  */
+
+/*
+       globals_of_w32fns is used to initialize those global variables that
+       must always be initialized on startup even when the global variable
+       initialized is non zero (see the function main in emacs.c).
+       globals_of_w32fns is called from syms_of_w32fns when the global
+       variable initialized is 0 and directly from main when initialized
+       is non zero.
+ */
+void
+globals_of_w32fns (void)
+{
+  HMODULE user32_lib = GetModuleHandle ("user32.dll");
+  /*
+    TrackMouseEvent not available in all versions of Windows, so must load
+    it dynamically.  Do it once, here, instead of every time it is used.
+  */
+  track_mouse_event_fn = (TrackMouseEvent_Proc)
+    GetProcAddress (user32_lib, "TrackMouseEvent");
+
+  monitor_from_point_fn = (MonitorFromPoint_Proc)
+    GetProcAddress (user32_lib, "MonitorFromPoint");
+  get_monitor_info_fn = (GetMonitorInfo_Proc)
+    GetProcAddress (user32_lib, "GetMonitorInfoA");
+  monitor_from_window_fn = (MonitorFromWindow_Proc)
+    GetProcAddress (user32_lib, "MonitorFromWindow");
+  enum_display_monitors_fn = (EnumDisplayMonitors_Proc)
+    GetProcAddress (user32_lib, "EnumDisplayMonitors");
+
+  {
+    HMODULE imm32_lib = GetModuleHandle ("imm32.dll");
+    get_composition_string_fn = (ImmGetCompositionString_Proc)
+      GetProcAddress (imm32_lib, "ImmGetCompositionStringW");
+    get_ime_context_fn = (ImmGetContext_Proc)
+      GetProcAddress (imm32_lib, "ImmGetContext");
+    release_ime_context_fn = (ImmReleaseContext_Proc)
+      GetProcAddress (imm32_lib, "ImmReleaseContext");
+    set_ime_composition_window_fn = (ImmSetCompositionWindow_Proc)
+      GetProcAddress (imm32_lib, "ImmSetCompositionWindow");
+  }
+
+  except_code = 0;
+  except_addr = 0;
+#ifndef CYGWIN
+  prev_exception_handler = SetUnhandledExceptionFilter (my_exception_handler);
+#endif
+
+  DEFVAR_INT ("w32-ansi-code-page",
+             w32_ansi_code_page,
+             doc: /* The ANSI code page used by the system.  */);
+  w32_ansi_code_page = GetACP ();
+
+  if (os_subtype == OS_NT)
+    w32_unicode_gui = 1;
+  else
+    w32_unicode_gui = 0;
+
+  /* MessageBox does not work without this when linked to comctl32.dll 6.0.  */
+  InitCommonControls ();
+
+  syms_of_w32uniscribe ();
+}
+
 #ifdef NTGUI_UNICODE
 
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