C / C++ / MFC

Matthew Faithfull wrote:

For example when matching template
parameters so int myfunc is the same function as int myfunc in some circumstances but not
in others.

template <class T> int myfunc (T a) {};

template <class T> int myfunc (const T a) {};

int myfunc (int a);
int myfunc (const int &a);

int myfunc (int a) {return 100;}

int myfunc (const int &a) {return 200;}

int main()
{
	myfunc (100);
	return 0;
}

1>d:\visual studio 2008\projects\test_const5\test_const5\main.cpp(7) : error C2668: 'myfunc' : ambiguous call to overloaded function
1>        d:\visual studio 2008\projects\test_const5\test_const5\main.cpp(3): could be 'int myfunc(const int &)'
1>        d:\visual studio 2008\projects\test_const5\test_const5\main.cpp(1): or       'int myfunc(int)'
1>        while trying to match the argument list '(int)'

Ben Aldhouse wrote:

I've been wondering why my recent article 'How To Calculate The Age Of A File' has been getting poor votes.

Ben Aldhouse wrote:

...I will assume that this is a flaw that people have spotted in my code...

WIN32_FIND_DATA FindFileData;
HANDLE hFind;
hFind = FindFirstFile(strPath, &FindFileData);
CString strYears, strMonths, strDays;

SYSTEMTIME stNow;
GetSystemTime(&stNow);
const FILETIME  ftFile = FindFileData.ftCreationTime;

FILETIME ftNow;
ULARGE_INTEGER ulNowTime, ulFileTime, ulAge;

SystemTimeToFileTime (& stNow, &ftNow);

ulNowTime.HighPart = ftNow.dwHighDateTime;
ulNowTime.LowPart = ftNow.dwLowDateTime;
ulFileTime.HighPart = ftFile.dwHighDateTime;
ulFileTime.LowPart = ftFile.dwLowDateTime;

ulAge.HighPart = ulNowTime.HighPart - ulFileTime.HighPart;
ulAge.LowPart = ulNowTime.LowPart - ulFileTime.LowPart;

FILETIME ftAge;
SYSTEMTIME stAge;

ftAge.dwHighDateTime = ulAge.HighPart;
ftAge.dwLowDateTime = ulAge.LowPart;

SystemTimeToFileTime(&stAge,&ftAge);

strYears.Format("%d", stAge.wYear-1601);
strMonths.Format("%d",stAge.wMonth-1);
strDays.Format("%d",stAge.wDay-1);

Remarks
    It is not recommended that you add and subtract values from the SYSTEMTIME 
    structure to obtain relative times. Instead, you should 

    -Convert the SYSTEMTIME structure to a FILETIME structure. 
    -Copy the resulting FILETIME structure to a ULARGE_INTEGER structure. 
    -Use normal 64-bit arithmetic on the ULARGE_INTEGER value. 

	WIN32_FIND_DATA FindFileData;
	HANDLE hFind;
	hFind = FindFirstFile(strPath, &FindFileData);
	CString strYears, strMonths, strDays;

	SYSTEMTIME stNow; 
	
//The current time is aquired and stored in SYSTEMTIME format
	GetSystemTime(&stNow);

//The creation time of the file in question is obtained and
//stored in FILETIME format
	const FILETIME  ftFile = FindFileData.ftCreationTime;

//A reference to the current time in FILETIME format is created
	FILETIME ftNow;
	WIN32_FIND_DATA FindFileData;
	HANDLE hFind;
	hFind = FindFirstFile(strPath, &FindFileData);
	CString strYears, strMonths, strDays;

	SYSTEMTIME stNow; 
	
//The current time is aquired and stored in SYSTEMTIME format

	GetSystemTime(&stNow);
	
//The creation time of the file in question is aquired in a FILETIME
//structure then converted inta a SYSTEMTIME structure

	const FILETIME  ftFile = FindFileData.ftCreationTime;
	FILETIME ftNow;
	SystemTimeToFileTime (& stNow, &ftNow);

//The contents of the FILETIME versions of the current time
//and the creation time of the file are now stored in 
//ULARGE_INTEGER structures

	ULARGE_INTEGER ulNowTime, ulFileTime, ulAge;
	ulNowTime.HighPart = ftNow.dwHighDateTime;
	ulNowTime.LowPart = ftNow.dwLowDateTime;
	ulFileTime.HighPart = ftFile.dwHighDateTime;
	ulFileTime.LowPart = ftFile.dwLowDateTime;

//The difference between the current time and the creation time
//of the file can now be created

	ulAge.HighPart = ulNowTime.HighPart - ulFileTime.HighPart;
	ulAge.LowPart = ulNowTime.LowPart - ulFileTime.LowPart;
	
	FILETIME ftAge;
	SYSTEMTIME stAge;

//The ULARGE_INTEGER data can then be copied back to a FILETIME
//structure, this can then be converted to SYSTEMTIME
//which is the convenient format we want our data to be in....

	ftAge.dwHighDateTime = ulAge.HighPart;
	ftAge.dwLowDateTime = ulAge.LowPart;

	FileTimeToSystemTime(&ftAge,&stAge);
	// not SystemTimeToFileTime(&stAge,&ftAge);!

	strYears.Format("%d", stAge.wYear-1601);
	strMonths.Format("%d",stAge.wMonth-1);
	strDays.Format("%d",stAge.wDay-1);