Given the following C++ program and its build error message, fix the code without affecting its functionality. First explain the reason, then output the whole fixed code.
If a function is missing, fix it by including the related libraries.

Code:
```
#include "tinyxml2/tinyxml2.h"
#include <string>
#include <stddef.h>
#include <stdint.h>

#if defined( _MSC_VER ) || defined (WIN32)
	#include <crtdbg.h>
	#define WIN32_LEAN_AND_MEAN
	#include <windows.h>
	_CrtMemState startMemState;
	_CrtMemState endMemState;
#else
	#include <sys/stat.h>
	#include <sys/types.h>
#endif

using namespace tinyxml2;
using namespace std;

// Entry point for LibFuzzer.
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
	std::string data_string(reinterpret_cast<const char*>(data), size);
	XMLDocument doc;
	doc.Parse( data_string.c_str() );
	doc.SaveFile();
	doc.Print();
	return 0;
}

```

Build error message:
/src/xmltest.cpp:25:6: error: no matching member function for call to 'SaveFile'
        doc.SaveFile();
        ~~~~^~~~~~~~
/src/tinyxml2/tinyxml2.h:1777:14: note: candidate function not viable: requires at least argument 'filename', but no arguments were provided
    XMLError SaveFile( const char* filename, bool compact = false );
             ^
/src/tinyxml2/tinyxml2.h:1786:14: note: candidate function not viable: requires at least argument 'fp', but no arguments were provided
    XMLError SaveFile( FILE* fp, bool compact = false );
             ^
1 error generated.

Fixed code: