put_time returning time zone as "Easter"

[jrobichaux]

In the latest emscripten, a call to std::put_time( std::localtime(&t_time), "%Z" ) on my Windows machine returns "Easter" instead of "Eastern Daylight Time".

This worked properly on the previous version I was using (3.1.51).

Minimal repro:

time_test.cpp

#include <ctime>
#include <iomanip>
#include <iostream>

int main()
{
	std::time_t t_time = std::time( NULL );
	std::cout << "time zone = " << std::put_time( std::localtime(&t_time), "%Z" ) << std::endl;
	return 0;
}

Compile with:
em++ time_test.cpp

Run with:
node a.out.js

On my machine (Windows 10) this returns "time zone = Easter". If I compile as a standard Windows executable it properly returns "time zone = Eastern Daylight Time".

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.56 (cf90417346b78455089e64eb909d71d091ecc055)
clang version 19.0.0git (https:/github.com/llvm/llvm-project 34ba90745fa55777436a2429a51a3799c83c6d4c)
Target: wasm32-unknown-emscripten
Thread model: posix

[sbc100]

I believe this is due to #21375.

The max number of chars in timezone name in POSIX is defined to be 6 (

emscripten/system/lib/libc/musl/include/limits.h

Line 151 in 2316d8a

#define _POSIX_TZNAME_MAX 6

) and musl's internal data structures use this limit.

If we could fix node on windows to give the abbreviated name (EDT) would that be enough to fix your issue? Or do you really need/want to full unabbreviated name?

[jrobichaux]

Wow, fast answer. Abbreviated name works for me, that's what we're getting on iOS and Mac already.

Thanks!

[sbc100]

Sadly I couldn't find any easy way to get such names on windows :(

BTW is node your target environment or it the browser? Do you know if the same results are produced when running the browser on windows?

[jrobichaux]

It's a browser app. I get the same (Easter) when I run it on Chrome in Windows.

[sbc100]

OK, in that case I think we need to increase out TZNAME_MAX so allow for these windows timezone names.

[jrobichaux]

If it helps, the TIME_ZONE_INFORMATION struct uses a max length of 32 for Windows timezone names.

Ironically the example on that page shows a return value of "EST" for the StandardName and DaylightName, but when I call GetTimeZoneInformation I get the full "Eastern Daylight Time".

[sbc100]

Thanks @jrobichaux , do you happen to know if there is any way to access the StandardName on the web or under node? I'm guessing the answer is no?

[jrobichaux]

do you happen to know if there is any way to access the StandardName on the web or under node? I'm guessing the answer is no?

Not that I know of. I was just thinking if you were going to increase the size of TZNAME_MAX then 32 should be a good number.

But I saw what you did in #21585 by using Javascript directly, and that's a good/clever workaround. Thanks!