which header file contains ThrowIfFailed() in DirectX 12 - c++

Question

some part of code image, another part of code image, I am beginner to DirectX 12 (or Game Programming) and studying from Microsoft documentation. While using function ThrowIfFailed() I get an error from intellisense of vs2015 editor
This declaration has no storage class or type specifier.
Can anyone help.

Answer 1

As you are new to DirectX programming, I strongly recommend starting with DirectX 11 rather than DirectX 12. DirectX 12 assumes you are already an expert DirectX 11 developer, and is a quite unforgiving API. It's absolutely worth learning if you plan to be a graphics developer, but starting with DX 12 over DX 11 is a huge undertaking. See the DirectX Tool Kit tutorials for DX11 and/or DX12
For modern DirectX sample code and in the VS DirectX templates, Microsoft uses a standard helper function ThrowIfFailed. It's not part of the OS or system headers; it's just defined in the local project's Precompiled Header File (pch.h):
#include <exception>
namespace DX
{
inline void ThrowIfFailed(HRESULT hr)
{
if (FAILED(hr))
{
// Set a breakpoint on this line to catch DirectX API errors
throw std::exception();
}
}
}
For COM programming, you must check at runtime all HRESULT values for failure. If it's safe to ignore the return value of a particular DirectX 11 or DirectX 12 API, it will return void instead. You generally use ThrowIfFailed for 'fast fail' scenarios (i.e. your program can't recover if the function fails).
Note the recommendation is to use C++ Exception Handling (a.k.a. /EHsc) which is the default compiler setting in the VS templates. On the x64 and ARM platforms, this is implemented very efficiently without any additional code overhead. Legacy x86 requires some additional epilog/prologue code that the compiler creates. Most of the "FUD" around exception handling in native code is based on the experience of using the older Asynchronous Structured Exception Handling (a.k.a. /EHa) which severely hampers the code optimizer.
See this wiki page for a bit more detail and usage information. You should also read the page on ComPtr.
In my version of the Direct3D Game VS Templates on GitHub, I use a slightly enhanced version of ThrowIfFailed which you could also use:
#include <exception>
namespace DX
{
// Helper class for COM exceptions
class com_exception : public std::exception
{
public:
com_exception(HRESULT hr) : result(hr) {}
virtual const char* what() const override
{
static char s_str[64] = {};
sprintf_s(s_str, "Failure with HRESULT of %08X",
static_cast<unsigned int>(result));
return s_str;
}
private:
HRESULT result;
};
// Helper utility converts D3D API failures into exceptions.
inline void ThrowIfFailed(HRESULT hr)
{
if (FAILED(hr))
{
throw com_exception(hr);
}
}
}

Answer 2

This error is because some of your code are outside of any function.
Your error is just here :
void D3D12HelloTriangle::LoadPipeline() {
#if defined(_DEBUG) { //<= this brack is simply ignore because on a pre-processor line
ComPtr<ID3D12Debug> debugController;
if (SUCCEEDED(D3D12GetDebugInterface(IID_PPV_ARGS(&debugController)))) {
debugController->EnableDebugLayer();
}
} // So, this one closes method LoadPipeline
#endif
// From here, you are out of any function
ComPtr<IDXGIFactory4> factory;
ThrowIfFailed(CreateDXGIFactory1(IID_PPV_ARGS(&factory)));
So to correct it :
void D3D12HelloTriangle::LoadPipeline() {
#if defined(_DEBUG)
{ //<= just put this bracket on it's own line
ComPtr<ID3D12Debug> debugController;
if (SUCCEEDED(D3D12GetDebugInterface(IID_PPV_ARGS(&debugController)))) {
debugController->EnableDebugLayer();
}
} // So, this one close method LoadPipeline
#endif
// From here, you are out of any function
ComPtr<IDXGIFactory4> factory;
ThrowIfFailed(CreateDXGIFactory1(IID_PPV_ARGS(&factory)));