Implement backtrace output for fatal errors on MS-Windows.

 src/w32fns.c (CaptureStackBackTrace_proc): New typedef.
 (BACKTRACE_LIMIT_MAX): New macro.
 (w32_backtrace): New function.
 (emacs_abort): Use w32_backtrace when the user chooses not to
 attach a debugger.  Update the text of the abort dialog.

2 files changed, 85 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 25cb1e76fa5..5739b5d9125 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2012-11-02  Eli Zaretskii  <eliz@gnu.org>
+
+        Implement backtrace output for fatal errors on MS-Windows.
+        * w32fns.c (CaptureStackBackTrace_proc): New typedef.
+        (BACKTRACE_LIMIT_MAX): New macro.
+        (w32_backtrace): New function.
+        (emacs_abort): Use w32_backtrace when the user chooses not to
+        attach a debugger.  Update the text of the abort dialog.
+
 2012-11-02  Dmitry Antipov  <dmantipov@yandex.ru>
 
         Window-related stuff cleanup here and there.
diff --git a/src/w32fns.c b/src/w32fns.c
index aa120d59ce5..7459c4a31db 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -26,6 +26,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <limits.h>
 #include <errno.h>
 #include <math.h>
+#include <fcntl.h>
 
 #include "lisp.h"
 #include "w32term.h"
@@ -7697,6 +7698,30 @@ globals_of_w32fns (void)
   syms_of_w32uniscribe ();
 }
 
+typedef USHORT (WINAPI * CaptureStackBackTrace_proc) (ULONG, ULONG, PVOID *,
+                                                      PULONG);
+
+#define BACKTRACE_LIMIT_MAX 62
+
+int
+w32_backtrace (void **buffer, int limit)
+{
+  static CaptureStackBackTrace_proc s_pfn_CaptureStackBackTrace = NULL;
+  HMODULE hm_kernel32 = NULL;
+
+  if (!s_pfn_CaptureStackBackTrace)
+    {
+      hm_kernel32 = LoadLibrary ("Kernel32.dll");
+      s_pfn_CaptureStackBackTrace =
+        (CaptureStackBackTrace_proc) GetProcAddress (hm_kernel32,
+                                                     "RtlCaptureStackBackTrace");
+    }
+  if (s_pfn_CaptureStackBackTrace)
+    return s_pfn_CaptureStackBackTrace (0, min (BACKTRACE_LIMIT_MAX, limit),
+                                        buffer, NULL);
+  return 0;
+}
+
 void
 emacs_abort (void)
 {
@@ -7704,7 +7729,10 @@ emacs_abort (void)
   button = MessageBox (NULL,
                        "A fatal error has occurred!\n\n"
                        "Would you like to attach a debugger?\n\n"
-                       "Select YES to debug, NO to abort Emacs"
+                       "Select:\n"
+                       "YES -- to debug Emacs, or\n"
+                       "NO  -- to abort Emacs and produce a backtrace\n"
+                       "       (emacs_backtrace.txt in current directory)."
 #if __GNUC__
                        "\n\n(type \"gdb -p <emacs-PID>\" and\n"
                        "\"continue\" inside GDB before clicking YES.)"
@@ -7719,7 +7747,52 @@ emacs_abort (void)
       exit (2); /* tell the compiler we will never return */
     case IDNO:
     default:
-      abort ();
-      break;
+      {
+        void *stack[BACKTRACE_LIMIT_MAX + 1];
+        int i = w32_backtrace (stack, BACKTRACE_LIMIT_MAX + 1);
+
+        if (i)
+          {
+            HANDLE errout = GetStdHandle (STD_ERROR_HANDLE);
+            int stderr_fd = -1, errfile_fd = -1;
+            int j;
+
+            if (errout && errout != INVALID_HANDLE_VALUE)
+              stderr_fd = _open_osfhandle ((intptr_t)errout, O_APPEND | O_BINARY);
+            if (stderr_fd >= 0)
+              write (stderr_fd, "\r\nBacktrace:\r\n", 14);
+            errfile_fd = _open ("emacs_backtrace.txt", O_RDWR | O_CREAT | O_BINARY, S_IREAD | S_IWRITE);
+            if (errfile_fd >= 0)
+              {
+                lseek (errfile_fd, 0L, SEEK_END);
+                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", stack[j] - sizeof(void *));
+                if (stderr_fd >= 0)
+                  write (stderr_fd, buf, strlen (buf));
+                if (errfile_fd >= 0)
+                  write (errfile_fd, buf, strlen (buf));
+              }
+            if (i == BACKTRACE_LIMIT_MAX)
+              {
+                if (stderr_fd >= 0)
+                  write (stderr_fd, "...\r\n", 5);
+                if (errfile_fd >= 0)
+                  write (errfile_fd, "...\r\n", 5);
+              }
+            if (errfile_fd >= 0)
+              close (errfile_fd);
+          }
+        abort ();
+        break;
+      }
     }
 }