write minidumps for unhandled exceptions on Windows

This will write a file mongo.dmp in the current directory when you crash.
You can open this dump with windbg and examine all thread stacks and locals.
To read and parse the exception details, issue the .ecxr command.

SConstruct

@@ -625,7 +625,7 @@ elif "win32" == os.sys.platform:
     else:
         env.Append( LINKFLAGS=" /NODEFAULTLIB:MSVCPRT  /NODEFAULTLIB:MSVCRT  " )
 
-    winLibString = "ws2_32.lib kernel32.lib advapi32.lib Psapi.lib"
+    winLibString = "ws2_32.lib kernel32.lib advapi32.lib Psapi.lib DbgHelp.lib"
 
     if force64:
 

src/mongo/db/db.cpp

@@ -48,6 +48,7 @@
 
 #if defined(_WIN32)
 # include "../util/ntservice.h"
+# include <DbgHelp.h>
 #else
 # include <sys/file.h>
 #endif
@@ -1253,6 +1254,48 @@ namespace mongo {
 
     LPTOP_LEVEL_EXCEPTION_FILTER filtLast = 0;
 
+    /* create a process dump.
+        To use, load up windbg.  Set your symbol and source path.
+        Open the crash dump file.  To see the crashing context, use .ecxr
+        */
+    void doMinidump(struct _EXCEPTION_POINTERS* exceptionInfo) {
+        LPCWSTR dumpFilename = L"mongo.dmp";
+        HANDLE hFile = CreateFileW(dumpFilename,
+            GENERIC_WRITE,
+            0,
+            NULL,
+            CREATE_ALWAYS,
+            FILE_ATTRIBUTE_NORMAL,
+            NULL);
+        if ( INVALID_HANDLE_VALUE == hFile ) {
+            DWORD lasterr = GetLastError();
+            log() << "failed to open minidump file " << dumpFilename << " : " 
+                  << errnoWithDescription( lasterr ) << endl;
+            return;
+        }
+
+        MINIDUMP_EXCEPTION_INFORMATION aMiniDumpInfo;
+        aMiniDumpInfo.ThreadId = GetCurrentThreadId();
+        aMiniDumpInfo.ExceptionPointers = exceptionInfo;
+        aMiniDumpInfo.ClientPointers = TRUE;
+
+        log() << "writing minidump dignostic file " << dumpFilename << endl;
+        BOOL bstatus = MiniDumpWriteDump(GetCurrentProcess(),
+            GetCurrentProcessId(),
+            hFile,
+            MiniDumpNormal,
+            &aMiniDumpInfo,
+            NULL,
+            NULL);
+        if ( FALSE == bstatus ) {
+            DWORD lasterr = GetLastError();
+            log() << "failed to create minidump : " 
+                  << errnoWithDescription( lasterr ) << endl;
+        }
+
+        CloseHandle(hFile);
+    }
+
     LONG WINAPI exceptionFilter( struct _EXCEPTION_POINTERS *excPointers ) {
         char exceptionString[128];
         sprintf_s( exceptionString, sizeof( exceptionString ),
@@ -1285,6 +1328,8 @@ namespace mongo {
             log() << "*** access violation was a " << acTypeString << addressString << endl;
         }
 
+        doMinidump(excPointers);
+
         // In release builds, let dbexit() try to shut down cleanly
 #if !defined(_DEBUG)
         dbexit( EXIT_UNCAUGHT, "unhandled exception" );