How is it possible to redirect TRACE statements in MFC to reduce the data stream from AfxDumpStack()?

Question

I saw from AfxDumpStack that one can redirect TRACE output.

• AFX_STACK_DUMP_TARGET_TRACE Sends output by means of the TRACE macro. The TRACE macro generates output in debug builds only; it generates no output in release builds. Also, TRACE can be redirected to other targets besides the debugger.

The italics is mine.

I'm programming in C++ from an old application and would like to dump part of the stack using AfxDumpStack() which only outputs to TRACE or the clipboard. I want to output only a few of the lines, so I need to process the string prior to output.

How would I accomplish this in the simplest way possible?

EDIT

So this is the code for my solution:

class hook
{
public:
    hook()
    {
        VERIFY(_CrtSetReportHook2(_CRT_RPTHOOK_INSTALL, Hook) != -1);
        _CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_FILE);
        _CrtSetReportFile(_CRT_WARN, INVALID_HANDLE_VALUE);
    }
    ~hook()
    {
        _CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_DEBUG);
        VERIFY(_CrtSetReportHook2(_CRT_RPTHOOK_REMOVE, Hook) != -1);
    }
    static const size_t max_backtrace = 4;    // max calls to view
    static const size_t skip_stack_head = -5; // skips over calls related to AfxDumpStack()
    static size_t line;                       // current line being output from begin of stack dump
    static bool stack_out;                    // currently outputting stack dump
    static int Hook( int reportType, char *message, int *returnValue )
    {
        if (strcmp(message, "=== begin AfxDumpStack output ===\r\n") == 0)
        {
            stack_out = true;
            line = skip_stack_head;
        }
        else if (strcmp(message, "=== end AfxDumpStack() output ===\r\n") == 0)
        {
            OutputDebugString("\r\n");
            stack_out = false;
        }
        else
        {
            if (strcmp(message, "\r\n") == 0) // AfxStackDump() sends CRLF out on separate calls
            {
                if (!stack_out || line < max_backtrace-1)
                {
                    OutputDebugString("\r\n\t");
                }
                ++line;
            }
            else if (!stack_out || line < max_backtrace)
            {
                OutputDebugString(message);
            }
        }
        return TRUE;
    }
};
size_t hook::line     = -1;
bool   hook::stack_out = false;

static hook junk;

The only problem is that the call to AfxDumpStack() requires a spawning of a thread. If called too much, this will kill the performance of the application.

Answer 1

By default, TRACE calls OutputDebugString.

You could use DebugView, which captures OutputDebugString output and has an option to log it to a file.

It doesn't seem to be possible to directly send the output to a file other than by changing the application, e.g. by hooking the output with _CrtSetReportHook2.

Internally, MFC uses _CrtDbgReport to output its TRACE messages. You can call _CrtSetReportMode to specify where its output should go. Having done this you can call _CrtSetReportFile to specify the win32 file handle (as returned by CreateFile).