[Buildroot] [PATCH v2] package/cvs: fix mktime related compile failure

Thomas Petazzoni thomas.petazzoni at bootlin.com
Fri May 29 06:09:48 UTC 2020

On Thu, 28 May 2020 23:59:12 +0200
Peter Seiderer <ps.report at gmx.net> wrote:

> Use ac_cv_func_working_mktime=yes to force the use of a provided
> mktime implementation instead of compiling the failing own one.
> Fixes:
>   http://autobuild.buildroot.net/results/5bcd8f4235002da682cc900f866116d2fe87f1c8
>   mktime.c: In function 'ydhms_diff':
>   mktime.c:106:52: error: size of array 'a' is negative
>    #define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
>                                                       ^
>   mktime.c:170:3: note: in expansion of macro 'verify'
>      verify (long_int_year_and_yday_are_wide_enough,
>      ^~~~~~
> with the failure/assert comming from the lines:
>   verify (long_int_year_and_yday_are_wide_enough,
>           INT_MAX <= LONG_MAX / 2 || TIME_T_MAX <= UINT_MAX);

Wait wait, this is verifying that TIME_T_MAX is lower than UINT_MAX, so
I guess the rest of the code assumes that the size of time_t is less or
equal than the size of an unsigned int.

With the time_t conversion to 64bit, time_t *is* larger than an
unsigned int.

So aren't you papering over the problem, and in fact potentially
causing some issues in CVS, which seems to assume the time_t fits in
32-bit ?

Or maybe I'm wrong here, because I see AlpineLinux simply updates the
mktime configure test to fix this issue:


Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering

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