https://bugzilla.kernel.org/show_bug.cgi?id=46731 Summary: difftime(3) may suggest that time_t can be a non-arithmetic type Product: Documentation Version: unspecified Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: man-pages AssignedTo: documentation_man-pages@xxxxxxxxxxxxxxxxxxxx ReportedBy: mgorny@xxxxxxxxxx Regression: No Created an attachment (id=78851) --> (https://bugzilla.kernel.org/attachment.cgi?id=78851) Patch changing the wording to the more exact problem The difftime(3) manpage[1] states: NOTES On a POSIX system, time_t is an arithmetic type, and one could just define #define difftime(t1,t0) (double)(t1 - t0) when the possible overflow in the subtraction is not a concern. On other systems, the data type time_t might use some other encoding where subtraction doesn't work directly. --- When I first read this, I got confused that time_t may actually be a non-arithmetic type. But the C99 standard explicitly lists (in 7.23.1): 3 The types declared are size_t (described in 7.17); clock_t and time_t which are arithmetic types capable of representing times --- I think that particular paragraphs should be re-worked to explicitly state what differences can arise in time_t implementations and what is the reason that they can't be used to compute time differences. As far as I understand, the only issue is that time_t can express time in units other than seconds. I'm attaching a patch with my wording for that. [1]:http://man7.org/linux/man-pages/man3/difftime.3.html -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
