ExceptionWithCallStack.cpp

//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
//
// ExceptionWithCallStack.cpp : Defines the CNTK exception and stack utilities
//
#include "stdafx.h"
#include "ExceptionWithCallStack.h"
#include "Basics.h"
#ifdef _WIN32
#pragma warning(push)
#pragma warning(disable: 4091) // 'typedef ': ignored on left of '' when no variable is declared
#include "DbgHelp.h"
#pragma warning(pop)
#include <WinBase.h>
#endif
#include <algorithm>
#include <iostream>

namespace Microsoft { namespace MSR { namespace CNTK {

using namespace std;

static string MakeFunctionNameStandOut(string name);
static void CollectCallStack(size_t skipLevels, bool makeFunctionNamesStandOut, const function<void(string)>& write);

namespace DebugUtil
{
    /// <summary>This function retrieves the call stack as a string</summary>
    string GetCallStack(size_t skipLevels /*= 0*/, bool makeFunctionNamesStandOut /*= false*/)
    {
        try
        {
            string output;
            string previousLine;
            int count = 1;
            CollectCallStack(skipLevels + 1/*skip this function*/, makeFunctionNamesStandOut, [&output, &previousLine, &count](const string& currentStackLine)
            {
                if (currentStackLine.compare(previousLine))
                {
                    if (count > 1)
                    {
                        output.pop_back(); // remove new line and add it below
                        output += " (x" + std::to_string(count) + ")\n"; // print callstack line plus number of times it appears
                    }
                    output += currentStackLine;
                    previousLine = currentStackLine;
                    count = 1;
                    return;
                }
                // make sure we're not counting empty lines
                if (!currentStackLine.empty())
                {
                    ++count;
                }
            });
            return output;
        }
        catch (...) // since we run as part of error reporting, don't get hung up on our own error
        {
            return string();
        }
    }

    /// <summary>This function outputs the call stack to the std err</summary>
    void PrintCallStack(size_t skipLevels /*= 0*/, bool makeFunctionNamesStandOut /*= false*/)
    {
        CollectCallStack(skipLevels + 1/*skip this function*/, makeFunctionNamesStandOut, [](string stack)
        {
            cerr << stack;
        });
    }
}

// make the unmangled name a bit more readable
// Insert spaces around the main function name for better visual parsability; and double-spaces between function arguments.
// This uses some heuristics for C++ names that may be fragile, but that's OK since this only adds/removes spaces.
static string MakeFunctionNameStandOut(string origName)
{
    try // guard against exception, since this is used for exception reporting
    {
        auto name = origName;
        // strip off modifiers for parsing (will be put back at the end)
        string modifiers;
        auto pos = name.find_last_not_of(" abcdefghijklmnopqrstuvwxyz");
        if (pos != string::npos)
        {
            modifiers = name.substr(pos + 1);
            name = name.substr(0, pos + 1);
        }
        bool hasArgList = !name.empty() && name.back() == ')';
        size_t angleDepth = 0;
        size_t parenDepth = 0;
        bool hitEnd = !hasArgList; // hit end of function name already?
        bool hitStart = false;
        // we parse the function name from the end; escape nested <> and ()
        // We look for the end and start of the function name itself (without namespace qualifiers),
        // and for commas separating function arguments.
        for (size_t i = name.size(); i--> 0;)
        {
            // account for nested <> and ()
            if (name[i] == '>')
                angleDepth++;
            else if (name[i] == '<')
                angleDepth--;
            else if (name[i] == ')')
                parenDepth++;
            else if (name[i] == '(')
                parenDepth--;
            // space before '>'
            if (name[i] == ' ' && i + 1 < name.size() && name[i + 1] == '>')
                name.erase(i, 1); // remove
            // commas
            if (name[i] == ',')
            {
                if (i + 1 < name.size() && name[i + 1] == ' ')
                    name.erase(i + 1, 1);  // remove spaces after comma
                if (!hitEnd && angleDepth == 0 && parenDepth == 1)
                    name.insert(i + 1, "  "); // except for top-level arguments, we separate them by 2 spaces for better readability
            }
            // function name
            if ((name[i] == '(' || name[i] == '<') &&
                parenDepth == 0 && angleDepth == 0 &&
                (i == 0 || name[i - 1] != '>') &&
                !hitEnd && !hitStart) // we hit the start of the argument list
            {
                hitEnd = true;
                name.insert(i, "  ");
            }
            else if ((name[i] == ' ' || name[i] == ':' || name[i] == '>') && hitEnd && !hitStart && i > 0) // we hit the start of the function name
            {
                if (name[i] != ' ')
                    name.insert(i + 1, " ");
                name.insert(i + 1, " "); // in total insert 2 spaces
                hitStart = true;
            }
        }
        return name + modifiers;
    }
    catch (...)
    {
        return origName;
    }
}

/// <summary>This function collects the stack tracke and writes it through the provided write function
/// <param name="write">Function for writing the text associated to a the callstack</param>
/// <param name="newline">Function for writing and "end-of-line" / "newline"</param>
/// </summary>
static void CollectCallStack(size_t skipLevels, bool makeFunctionNamesStandOut, const function<void(string)>& write)
{
    static const int MAX_CALLERS = 62;
    static const unsigned short MAX_CALL_STACK_DEPTH = 20;

    write("\n[CALL STACK]\n");

#ifdef _WIN32

    // RtlCaptureStackBackTrace() is a kernel API without default binding, we must manually determine its function pointer.
    typedef USHORT(WINAPI * CaptureStackBackTraceType)(__in ULONG, __in ULONG, __out PVOID*, __out_opt PULONG);
    CaptureStackBackTraceType RtlCaptureStackBackTrace = (CaptureStackBackTraceType)(GetProcAddress(LoadLibrary(L"kernel32.dll"), "RtlCaptureStackBackTrace"));
    if (RtlCaptureStackBackTrace == nullptr) // failed somehow
        return write("Failed to generate CALL STACK. GetProcAddress(\"RtlCaptureStackBackTrace\") failed with error " + msra::strfun::utf8(FormatWin32Error(GetLastError())) + "\n");

    HANDLE process = GetCurrentProcess();
    if (!SymInitialize(process, nullptr, TRUE))
        return write("Failed to generate CALL STACK. SymInitialize() failed with error " + msra::strfun::utf8(FormatWin32Error(GetLastError())) + "\n");

    // get the call stack
    void* callStack[MAX_CALLERS];
    unsigned short frames;
    frames = RtlCaptureStackBackTrace(0, MAX_CALLERS, callStack, nullptr);

    SYMBOL_INFO* symbolInfo = (SYMBOL_INFO*)calloc(sizeof(SYMBOL_INFO) + 256 * sizeof(char), 1); // this is a variable-length structure, can't use vector easily
    symbolInfo->MaxNameLen = 255;
    symbolInfo->SizeOfStruct = sizeof(SYMBOL_INFO);
    frames = min(frames, MAX_CALL_STACK_DEPTH);

    // format and emit
    size_t firstFrame = skipLevels + 1; // skip CollectCallStack()
    for (size_t i = firstFrame; i < frames; i++)
    {
        string callStackLine;
        if (i == firstFrame)
            callStackLine = "    > ";
        else
            callStackLine = "    - ";

        if (SymFromAddr(process, (DWORD64)(callStack[i]), 0, symbolInfo))
        {
            callStackLine += makeFunctionNamesStandOut ? MakeFunctionNameStandOut(symbolInfo->Name) : symbolInfo->Name;
            write(callStackLine + "\n");
        }
        else
        {
            DWORD error = GetLastError();
            char buf[17];
            sprintf_s(buf, "%p", callStack[i]);
            callStackLine += buf;
            write(callStackLine + " (SymFromAddr() error: " + msra::strfun::utf8(FormatWin32Error(error)) + ")\n");
        }
    }

    write("\n");

    free(symbolInfo);

    SymCleanup(process);

#else // Linux

    unsigned int MAX_NUM_FRAMES = 1024;
    void* backtraceAddresses[MAX_NUM_FRAMES];
    unsigned int numFrames = backtrace(backtraceAddresses, MAX_NUM_FRAMES);
    char** symbolList = backtrace_symbols(backtraceAddresses, numFrames);

    for (size_t i = skipLevels; i < numFrames; i++)
    {
        char* beginName    = NULL;
        char* beginOffset  = NULL;
        char* beginAddress = NULL;

        // Find parentheses and +address offset surrounding the mangled name
        for (char* p = symbolList[i]; *p; ++p)
        {
            if (*p == '(')      // function name begins here
                beginName = p;
            else if (*p == '+') // relative address ofset
                beginOffset = p;
            else if ((*p == ')') && (beginOffset || beginName)) // absolute address
                beginAddress = p;
        }
        const int buf_size = 1024;
        char buffer[buf_size];

        if (beginName && beginAddress && (beginName < beginAddress))
        {
            *beginName++ = '\0';
            *beginAddress++ = '\0';
            if (beginOffset) // has relative address
                *beginOffset++ = '\0';

            // Mangled name is now in [beginName, beginOffset) and caller offset in [beginOffset, beginAddress).
            int status = 0;
            unsigned int MAX_FUNCNAME_SIZE = 4096;
            size_t funcNameSize = MAX_FUNCNAME_SIZE;
            char funcName[MAX_FUNCNAME_SIZE]; // working buffer
            const char* ret = abi::__cxa_demangle(beginName, funcName, &funcNameSize, &status);
            string fName;
            if (status == 0)
                fName = makeFunctionNamesStandOut ? MakeFunctionNameStandOut(ret) : ret; // make it a bit more readable
            else
                fName = beginName; // failed: fall back

            // name of source file--not printing since it is not super-useful
            //string sourceFile = symbolList[i];
            //static const size_t sourceFileWidth = 20;
            //if (sourceFile.size() > sourceFileWidth)
            //    sourceFile = "..." + sourceFile.substr(sourceFile.size() - (sourceFileWidth-3));
            while (*beginAddress == ' ') // eat unnecessary space
                beginAddress++;
            string pcOffset = beginOffset ? string(" + ") + beginOffset : string();
            snprintf(buffer, buf_size, "%-20s%-50s%s\n", beginAddress, fName.c_str(), pcOffset.c_str());
        }
        else // Couldn't parse the line. Print the whole line as it came.
            snprintf(buffer, buf_size, "%s\n", symbolList[i]);

        write(buffer);
    }

    free(symbolList);

#endif
}

template class ExceptionWithCallStack<std::runtime_error>;
template class ExceptionWithCallStack<std::logic_error>;
template class ExceptionWithCallStack<std::invalid_argument>;

}}}