Debug Logging on Windows in Modern C++

DebuggingHelpers.h

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// DebuggingHelpers.h : Debug Logging on Windows in Modern C++
//
// Author Name :
//      Darrin W. Cullop ([email protected])
//
// License :
//      CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
//
// Abstract :
//      Simple "PrintF" Logging to the Debugger on Windows.  Works with ANSI and Wide Strings (use %S when mixing).
//      Use "DebugTrace" to only emit in Debug Builds.  Use "Trace" to always emit.
//
// Example Usages:
//      dwc::Trace( "Hello, World! The number is %d!\r\n", 37 );
//      dwc::DebugTrace( L"Hello, World! The number is %d!\r\n", 42 );
//      dwc::Trace( "Received Wide String: [%S]\r\n", lpszWideString ); // Uses wide with a skinny format
//      dwc::Trace( L"Received Wide String: [%s]\r\n", lpszWideString );
//      dwc::DebugTrace( L"Received Skinny String: [%S]\r\n", lpszSkinnyString ); // Uses skinny with a wide format
//      dwc::DebugTrace( "Received Skinny String: [%s]\r\n", lpszSkinnyString );
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#pragma once

#include <string>
#include <cstdio>
#include <cwchar>

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// dwc Namespace
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

namespace dwc
{
    template<typename... Args>
    inline void Trace( const char* const lpszFormat, Args&&... args ) noexcept
    {
        try
        {
            // Don't allocate a buffer unless extra arguments are provided
            if constexpr ( sizeof...( args ) > 0 )
            {
                const auto charsNeeded = std::snprintf( nullptr, 0, lpszFormat, args... );
                auto       output      = std::string( charsNeeded + 1UL, '\0' );
                const auto charsUsed   = std::snprintf( output.data(), output.size(), lpszFormat, args... );

                // Emit the formatted buffer
                ::OutputDebugStringA( output.c_str() );
            }
            else
            {
                // Only one argument provided, so just emit the string
                ::OutputDebugStringA( lpszFormat );
            }
            return;
        }
        catch( ... )
        {
            ::OutputDebugStringA( "Trace Failure!" );
            return;
        }
    }

    template<typename... Args>
    inline void Trace( const wchar_t* const lpszFormat, Args&&... args ) noexcept
    {
        try
        {
            // Don't allocate a buffer unless extra arguments are provided
            if constexpr ( sizeof...( args ) > 0 )
            {
                const auto charsNeeded = std::swprintf( nullptr, 0, lpszFormat, args... );
                auto       output      = std::wstring( charsNeeded + 1ULL, L'\0' );
                const auto charsUsed   = std::swprintf( output.data(), output.size(), lpszFormat, args... );

                // Emit the formatted buffer
                ::OutputDebugStringW( output.c_str() );
            }
            else
            {
                // Only one argument provided, so just emit the string
                ::OutputDebugStringW( lpszFormat );
            }
            return;
        }
        catch (...)
        {
            ::OutputDebugStringW( L"Trace Failure!" );
            return;
        }
    }
    
    template<typename... Args>
    inline void DebugTrace( Args&&... args ) noexcept
    {
#if defined(_DEBUG) || defined(DEBUG)
        // If the caller forgot something, help them out with a better error message
        static_assert( (sizeof...( args ) > 0), "Please provide at least one parameter" );
        
        // Will dispatch to the correct overload
        Trace( std::forward<Args>(args)... );
#endif
    }

    //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
}   // namespace dwc

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// End of DebuggingHelpers.h
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