That page is consistent with msvc implementation. OTOH glibc's implementation is weird for me.Actually that page is even more confusing, as it talks about "processing times" as well.
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/***
*clock_t clock() - Return the processor time used by this process.
*
*Purpose:
* This routine calculates how much time the calling process
* has used. At startup time, startup calls __inittime which stores
* the initial time. The clock routine calculates the difference
* between the current time and the initial time.
*
* Clock must reference _cinitime so that _cinitim.asm gets linked in.
* That routine, in turn, puts __inittime in the startup initialization
* routine table.
*
*Entry:
* No parameters.
* itime is a static structure of type timeb.
*
*Exit:
* If successful, clock returns the number of CLK_TCKs (milliseconds)
* that have elapsed. If unsuccessful, clock returns -1.
*
*Exceptions:
* None.
*
*******************************************************************************/
clock_t __cdecl clock (
void
)
{
unsigned __int64 current_tics;
FILETIME ct;
GetSystemTimeAsFileTime( &ct );
current_tics = (unsigned __int64)ct.dwLowDateTime +
(((unsigned __int64)ct.dwHighDateTime) << 32);
/* calculate the elapsed number of 100 nanosecond units */
current_tics -= start_tics;
/* return number of elapsed milliseconds */
return (clock_t)(current_tics / 10000);
}