www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Why is time_t defined as a 32-bit type on Windows?

reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
```
C:\dev> rdmd -m64 --eval="import core.stdc.time; 
writeln(time_t.sizeof);"
4
```

According to MSDN this should not be the case:

https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/time-time32-time64?view=vs-2019


 time is a wrapper for _time64 and **time_t is, by default, 
 equivalent to __time64_t**.


But in Druntime it's defined as a 32-bit type: 
https://github.com/dlang/druntime/blob/349d63750d55d078426d4f433cba512625f8a3a3/src/core/sys/windows/stdc/time.d#L42
Aug 05 2020
next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On Wednesday, 5 August 2020 at 16:13:19 UTC, Andrej Mitrovic 
wrote:

 ```
 C:\dev> rdmd -m64 --eval="import core.stdc.time; 
 writeln(time_t.sizeof);"
 4
 ```

 According to MSDN this should not be the case:

 https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/time-time32-time64?view=vs-2019


 time is a wrapper for _time64 and **time_t is, by default, 
 equivalent to __time64_t**.


 But in Druntime it's defined as a 32-bit type: 
 https://github.com/dlang/druntime/blob/349d63750d55d078426d4f433cba512625f8a3a3/src/core/sys/windows/stdc/time.d#L42


It looks like this definition was there from at least 2008 (!!), 
and probably earlier than that but I don't have the SVN sources: 
https://github.com/dlang/druntime/blob/6837c0cd426f7e828aec1a2bdc941ac9b722dd14/import/stdc/time.d#L49


So basically, just around the time the first 64-bit version of 
Windows was released. I'm guessing it was just neglected..
Aug 05 2020
prev sibling next sibling parent reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On Wednesday, 5 August 2020 at 16:13:19 UTC, Andrej Mitrovic 
wrote:

 ```
 C:\dev> rdmd -m64 --eval="import core.stdc.time; 
 writeln(time_t.sizeof);"
 4
 ```

 According to MSDN this should not be the case:

 https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/time-time32-time64?view=vs-2019


 time is a wrapper for _time64 and **time_t is, by default, 
 equivalent to __time64_t**.


 But in Druntime it's defined as a 32-bit type: 
 https://github.com/dlang/druntime/blob/349d63750d55d078426d4f433cba512625f8a3a3/src/core/sys/windows/stdc/time.d#L42


I filed it as an issue to get more eyes / feedback: 
https://issues.dlang.org/show_bug.cgi?id=21134
Aug 06 2020
parent Petar Kirov [ZombineDev] <petar.p.kirov gmail.com> writes:
On Friday, 7 August 2020 at 05:37:32 UTC, Andrej Mitrovic wrote:

 On Wednesday, 5 August 2020 at 16:13:19 UTC, Andrej Mitrovic 
 wrote:

 ```
 C:\dev> rdmd -m64 --eval="import core.stdc.time; 
 writeln(time_t.sizeof);"
 4
 ```

 According to MSDN this should not be the case:

 https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/time-time32-time64?view=vs-2019


 time is a wrapper for _time64 and **time_t is, by default, 
 equivalent to __time64_t**.


 But in Druntime it's defined as a 32-bit type: 
 https://github.com/dlang/druntime/blob/349d63750d55d078426d4f433cba512625f8a3a3/src/core/sys/windows/stdc/time.d#L42


 I filed it as an issue to get more eyes / feedback: 
 https://issues.dlang.org/show_bug.cgi?id=21134



As far as I gather, this was changed with MSVC 2005 [0], so 
perhaps the relevent change wasn't applied to the druntime 
windows bindings. Also keep in mind that we revamped a large 
portion of the Windows bindins in 2015 [1], whose code was based 
on MinGW IIRC.


 In versions of Visual C++ and Microsoft C/C++ before Visual 
 Studio 2005, time_t was a long int (32 bits) and hence could 
 not be used for dates past 3:14:07 January 19, 2038, UTC. 
 time_t is now equivalent to __time64_t by default, but defining 
 _USE_32BIT_TIME_T changes time_t to __time32_t and forces many 
 time functions to call versions that take the 32-bit time_t. 
 For more information, see Standard Types and comments in the 
 documentation for the individual time functions.


(^ Source [0])

[0]:
https://docs.microsoft.com/en-us/cpp/c-runtime-library/time-management?view=vs-2019
[1]: https://github.com/dlang/druntime/pull/1402

Edit: I see you're discussing core.stdc.time, which actually 
wasn't part of the changes in [1]. In any case, druntime should 
offer both time_t, __time32_t, and __time64_t, and have time_t 
time() default to 64-bit. I do wonder what exactly is exported 
from UCRT as time(), as from the docs it looks it should be just 
a macro, but if anyone had used time() one Windows (from D) and 
didn't get linker errors or memory corruption, then I suppose 
they're still defaulting it to 32-bit to avoid ABI breakages.
Aug 07 2020
prev sibling parent Kagamin <spam here.lot> writes:
Because it's used with C `time` function 
https://github.com/dlang/druntime/blob/master/src/core/stdc/time.d#L37 which is
provided by msvcrt as 32-bit function. 64-bit variant has a different name.
Aug 07 2020