8e6fd2bdb2
[BZ #23603][BZ #16346] This fixes some obscure problems with integer overflow. Although it looks scary, it is almost all a byte-for-byte copy from Gnulib, and the Gnulib code has been tested reasonably well. * include/intprops.h: New file, copied from Gnulib. * include/verify.h, time/mktime-internal.h: New tiny files, simplified from Gnulib. * time/mktime.c: Copy from Gnulib. This has the following changes: Do not include config.h if DEBUG_MKTIME is nonzero. Include stdbool.h, intprops.h, verify.h. Include string.h only if needed. Include stdlib.h on MS-Windows. Include mktime-internal.h. (DEBUG_MKTIME): Default to 0, and simplify later uses. (NEED_MKTIME_INTERNAL, NEED_MKTIME_WINDOWS) (NEED_MKTIME_WORKING): Give default values to pacify -Wundef, which glibc uses. Default NEED_MKTIME_WORKING to DEBUG_MKTIME, to simplify later conditionals; default the others to zero. Use these conditionals to express only the code needed on the current platform. In uses of these conditionals, explicitly spell out how _LIBC affects things, so it’s easier to review from a glibc viewpoint. (WRAPV): Remove; no longer needed now that we have systematic overflow checking. (my_tzset, __tzset) [!_LIBC]: New function and macro, to better compartmentalize tzset issues. Move system-dependent tzsettish code here from mktime. (verify): Remove; now done by verify.h. All uses changed. (long_int): Use a more-conservative definition, to avoid integer overflow. (SHR): Remove, replacing with ... (shr): New function, which means we needn’t worry about side effects in args, and conversion analysis is simpler. (TYPE_IS_INTEGER, TYPE_TWOS_COMPLEMENT, TYPE_SIGNED, TYPE_MINIMUM) (TYPE_MAXIMUM, TIME_T_MIN, TIME_T_MAX, TIME_T_MIDPOINT) (time_t_avg, time_t_add_ok): Remove. (mktime_min, mktime_max): New constants. (leapyear, isdst_differ): Use bool for booleans. (ydhms_diff, guess_time_tm, ranged_convert, __mktime_internal): Use long_int, not time_t, for mktime differences. (long_int_avg): New function, replacing time_t_avg. INT_ADD_WRAPV replaces time_t_add_ok. (guess_time_tm): 6th arg is now long_int, not time_t const *. All uses changed. (convert_time): New function. (ranged_convert): Use it. (__mktime_internal): Last arg now points to mktime_offset_t, not time_t. All uses changed. This is a no-op on glibc, where mktime_offset_t is always time_t. Use int, not time_t, for UTC offset guess. Directly check for integer overflow instead of using a heuristic that works only 99.9...% of the time. Access *OFFSET only once, to avoid an unlikely race if the compiler delays a load and if this cascades into a signed integer overflow. (mktime): Move tzsettish code to my_tzset, and move localtime_offset to within mktime so that it doesn’t need a separate ifdef. (main) [DEBUG_MKTIME]: Speed up by using localtime_r instead of localtime. * time/timegm.c: Copy from Gnulib. This has the following changes: Include mktime-internal.h. [!_LIBC]: Include config.h and time.h. Do not include timegm.h or time_r.h. Make __mktime_internal a macro, and include mktime-internal.h to get its declaration. (timegm): Temporary is now mktime_offset_t, not time_t. This affects only Gnulib.
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