c++ - How can you use CaptureStackBackTrace to capture the exception stack, not the calling stack?

Question

I marked up the following code:

#include "stdafx.h"
#include <process.h>
#include <iostream>
#include <Windows.h>
#include "dbghelp.h"

using namespace std;

#define TRACE_MAX_STACK_FRAMES 1024
#define TRACE_MAX_FUNCTION_NAME_LENGTH 1024

int printStackTrace()
{
    void *stack[TRACE_MAX_STACK_FRAMES];
    HANDLE process = GetCurrentProcess();
    SymInitialize(process, NULL, TRUE);
    WORD numberOfFrames = CaptureStackBackTrace(0, TRACE_MAX_STACK_FRAMES, stack, NULL);
    SYMBOL_INFO *symbol = (SYMBOL_INFO *)malloc(sizeof(SYMBOL_INFO)+(TRACE_MAX_FUNCTION_NAME_LENGTH - 1) * sizeof(TCHAR));
    symbol->MaxNameLen = TRACE_MAX_FUNCTION_NAME_LENGTH;
    symbol->SizeOfStruct = sizeof(SYMBOL_INFO);
    DWORD displacement;
    IMAGEHLP_LINE64 *line = (IMAGEHLP_LINE64 *)malloc(sizeof(IMAGEHLP_LINE64));
    line->SizeOfStruct = sizeof(IMAGEHLP_LINE64);
    for (int i = 0; i < numberOfFrames; i++)
    {
        DWORD64 address = (DWORD64)(stack[i]);
        SymFromAddr(process, address, NULL, symbol);
        if (SymGetLineFromAddr64(process, address, &displacement, line))
        {
            printf("at %s in %s: line: %lu: address: 0x%0X
", symbol->Name, line->FileName, line->LineNumber, symbol->Address);
        }
        else
        {
            printf("SymGetLineFromAddr64 returned error code %lu.
", GetLastError());
            printf("at %s, address 0x%0X.
", symbol->Name, symbol->Address);
        }
    }
    return 0;
}

void function2()
{
    int a = 0;
    int b = 0;
    throw new exception;
}

void function1()
{
    int a = 0;
    function2();
}

void function0()
{
    function1();
}

static void threadFunction(void *param)
{
    try
    {
        function0();
    }
    catch (...)
    {
        printStackTrace();
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    _beginthread(threadFunction, 0, NULL);
    printf("Press any key to exit.
");
    cin.get();
    return 0;
}

What it does is, it logs a stack trace, but the problem is that the stack trace it logs does not give me the line numbers that I want. I want it to log the line numbers of the places that threw the exception, on and up the call stack, kind of like in C#. But what it actually does right now, is it outputs the following:

        at printStackTrace in c:users<yourusername>documentsvisual studio 2013pr
ojectsstacktracingstacktracingstacktracing.cpp: line: 17: address: 0x10485C0
        at threadFunction in c:users<yourusername>documentsvisual studio 2013pro
jectsstacktracingstacktracingstacktracing.cpp: line: 68: address: 0x10457C0
        SymGetLineFromAddr64 returned error code 487.
        at beginthread, address 0xF9431E0.
        SymGetLineFromAddr64 returned error code 487.
        at endthread, address 0xF9433E0.
        SymGetLineFromAddr64 returned error code 487.
        at BaseThreadInitThunk, address 0x7590494F.
        SymGetLineFromAddr64 returned error code 487.
        at RtlInitializeExceptionChain, address 0x7713986A.
        SymGetLineFromAddr64 returned error code 487.
        at RtlInitializeExceptionChain, address 0x7713986A.

The problem I am facing, once again, is that line: 68 in this trace corresponds to the line that calls the method printStackTrace();, while I would like it to give me line number 45, which corresponds to the line which throws the exception: throw new exception; and then continue further up the stack.

How can I achieve this sort of behavior and break into this thread exactly when it throws this exception in order to get a proper stack trace?

PS The code above was run for a console application using MSVC++ with unicode enabled on Windows 8.1 x64 machine, with the application being run as a Win32 application in Debug mode.

Answer 1

On Windows, unhandled C++ exception automatically generates SEH exception. SEH __except block allows to attach a filter that accepts _EXCEPTION_POINTERS structure as a parameter, which contains the pointer to the processor's context record in the moment exception was thrown. Passing this pointer to StackWalk64 function gives the stack trace in the moment of exception. So, this problem can be solved by using SEH-style exception handling instead of C++ style.

Example code:

#include <stdlib.h>
#include <locale.h>
#include <stdio.h>
#include <tchar.h>

#include <process.h>
#include <iostream>
#include <Windows.h>
#include "dbghelp.h"

using namespace std;

const int MaxNameLen = 256;

#pragma comment(lib,"Dbghelp.lib")

void printStack( CONTEXT* ctx ) //Prints stack trace based on context record
{
    BOOL    result;
    HANDLE  process;
    HANDLE  thread;
    HMODULE hModule;

    STACKFRAME64        stack;
    ULONG               frame;    
    DWORD64             displacement;

    DWORD disp;
    IMAGEHLP_LINE64 *line;

    char buffer[sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR)];
    char name[MaxNameLen];
    char module[MaxNameLen];
    PSYMBOL_INFO pSymbol = (PSYMBOL_INFO)buffer;

    memset( &stack, 0, sizeof( STACKFRAME64 ) );

    process                = GetCurrentProcess();
    thread                 = GetCurrentThread();
    displacement           = 0;
#if !defined(_M_AMD64)
    stack.AddrPC.Offset    = (*ctx).Eip;
    stack.AddrPC.Mode      = AddrModeFlat;
    stack.AddrStack.Offset = (*ctx).Esp;
    stack.AddrStack.Mode   = AddrModeFlat;
    stack.AddrFrame.Offset = (*ctx).Ebp;
    stack.AddrFrame.Mode   = AddrModeFlat;
#endif

    SymInitialize( process, NULL, TRUE ); //load symbols

    for( frame = 0; ; frame++ )
    {
        //get next call from stack
        result = StackWalk64
        (
#if defined(_M_AMD64)
            IMAGE_FILE_MACHINE_AMD64
#else
            IMAGE_FILE_MACHINE_I386
#endif
            ,
            process,
            thread,
            &stack,
            ctx,
            NULL,
            SymFunctionTableAccess64,
            SymGetModuleBase64,
            NULL
        );

        if( !result ) break;        

        //get symbol name for address
        pSymbol->SizeOfStruct = sizeof(SYMBOL_INFO);
        pSymbol->MaxNameLen = MAX_SYM_NAME;
        SymFromAddr(process, ( ULONG64 )stack.AddrPC.Offset, &displacement, pSymbol);

        line = (IMAGEHLP_LINE64 *)malloc(sizeof(IMAGEHLP_LINE64));
        line->SizeOfStruct = sizeof(IMAGEHLP_LINE64);       

        //try to get line
        if (SymGetLineFromAddr64(process, stack.AddrPC.Offset, &disp, line))
        {
            printf("at %s in %s: line: %lu: address: 0x%0X
", pSymbol->Name, line->FileName, line->LineNumber, pSymbol->Address);
        }
        else
        { 
            //failed to get line
            printf("at %s, address 0x%0X.
", pSymbol->Name, pSymbol->Address);
            hModule = NULL;
            lstrcpyA(module,"");        
            GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, 
                (LPCTSTR)(stack.AddrPC.Offset), &hModule);

            //at least print module name
            if(hModule != NULL)GetModuleFileNameA(hModule,module,MaxNameLen);       

            printf ("in %s
",module);
        }       

        free(line);
        line = NULL;
    }
}

//******************************************************************************

void function2()
{
    int a = 0;
    int b = 0;
    throw exception();
}

void function1()
{
    int a = 0;
    function2();
}

void function0()
{
    function1();
}

int seh_filter(_EXCEPTION_POINTERS* ex)
{
    printf("*** Exception 0x%x occured ***

",ex->ExceptionRecord->ExceptionCode);    
    printStack(ex->ContextRecord);

    return EXCEPTION_EXECUTE_HANDLER;
}

static void threadFunction(void *param)
{    

    __try
    {
         function0();
    }
    __except(seh_filter(GetExceptionInformation()))
    {       
        printf("Exception 
");         
    }
}

int _tmain(int argc, _TCHAR* argv[])
{   
    _beginthread(threadFunction, 0, NULL);
    printf("Press any key to exit.
");
    cin.get();
    return 0;
}

Example output (first two entries are noise, but the rest correctly reflects functions that caused exception):

*** Exception 0xe06d7363 occured ***

        at RaiseException, address 0xFD3F9E20.
in C:Windowssystem32KERNELBASE.dll
        at CxxThrowException, address 0xDBB5A520.
in C:Windowssystem32MSVCR110D.dll
        at function2 in c:workprojectsestest.cpp: line: 146: address: 0x3F9C6C00
        at function1 in c:workprojectsestest.cpp: line: 153: address: 0x3F9C6CB0
        at function0 in c:workprojectsestest.cpp: line: 158: address: 0x3F9C6CE0
        at threadFunction in c:workprojectsestest.cpp: line: 174: address: 0x3F9C6D70
        at beginthread, address 0xDBA66C60.
in C:Windowssystem32MSVCR110D.dll
        at endthread, address 0xDBA66E90.
in C:Windowssystem32MSVCR110D.dll
        at BaseThreadInitThunk, address 0x773C6520.
in C:Windowssystem32kernel32.dll
        at RtlUserThreadStart, address 0x775FC520.
in C:WindowsSYSTEM32
tdll.dll

---

Another option is to create custom exception class that captures context in constructor and use it (or derived classes) to throw exceptions:

class MyException{
public:
    CONTEXT Context;

    MyException(){
        RtlCaptureContext(&Context);        
    }
};

void function2()
{    
    throw MyException();    
}

//...   

try
{
     function0();
}
catch (MyException& e)
{       
    printf("Exception 
");     
    printStack(&e.Context);                 
}