What are clock_t and time_t?

[jamadagni]

In the description of time.h I have read that clock_t and time_t are arithmetic types representing times, but I do not understand what exact datatypes these are - how many bytes they hold, etc. For instance, if I have:

#include <time.h>
time_t now;
now = time();

#include <time.h>
time_t now;
now = time();

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what formatting would I need to use if I use the variable now in a printf statement?

[munna]

what exact datatypes these

They are generally defined as long int.

[jacek]

how many bytes they hold

This you can always find out using sizeof().

[bood]

Why not find it out yourself by looking into the header file?

[jamadagni]

Why not find it out yourself by looking into the header file

/usr/include/time.h did not have any useful info.

[bood]

/usr/include/time.h did not have any useful info.

Pretty weird...
This from my gcc 3.4.3/mingw

#ifndef _CLOCK_T_DEFINED
typedef	long	clock_t;
#define _CLOCK_T_DEFINED
#endif
 
#ifndef _TIME_T_DEFINED
typedef	long	time_t;
#define _TIME_T_DEFINED
#endif

#ifndef _CLOCK_T_DEFINED
typedef	long	clock_t;
#define _CLOCK_T_DEFINED
#endif

#ifndef _TIME_T_DEFINED
typedef	long	time_t;
#define _TIME_T_DEFINED
#endif

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And it seems from the standard that it's implemention dependent

[GreyGeek]

/usr/include/time.h did not have any useful info.

mmm... Here is what the time.h header included with MSVC++ 6.0 has:

/* Define the implementation defined time type */
#ifndef _TIME_T_DEFINED
#ifdef  _WIN64
typedef __int64   time_t;       /* time value */
#else
typedef _W64 long time_t;       /* time value */
#endif
#define _TIME_T_DEFINED         /* avoid multiple def's of time_t */
#endif

/* Define the implementation defined time type */
#ifndef _TIME_T_DEFINED
#ifdef  _WIN64
typedef __int64   time_t;       /* time value */
#else
typedef _W64 long time_t;       /* time value */
#endif
#define _TIME_T_DEFINED         /* avoid multiple def's of time_t */
#endif

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That tells me exactly how time_t is defined.

[fullmetalcoder]

__int64 is obviously a 64bit (implicitly signed) integer which in pure C++ (i.e. : not polluted by Microsoft) is called a "long long int" .


edit:

to learn more about _W64 check out the files included by your time.h