timegm() and other time related functions

timegm() and other time related functions

[Sebastian Huber]

Hello,

while porting nats.c to RTEMS I noticed that Newlib doesn't provide a 
timegm() function. There a couple of related patches and discussions on 
the Newlib mailing list in the last years.

In order to add support for timegm() I would replace the Newlib time 
function implementation with the version of a more actively maintained 
platform, for example OpenBSD, FreeBSD or bionic. It seems that the 
upstream for the bionic code is OpenBSD. The OpenBSD and FreeBSD code 
diverged a bit, however, FreeBSD seems to integrate changes from OpenBSD 
occasionally. The FreeBSD looks to be closer to the original tzcode and 
uses the pthread API. I tend to use the FreeBSD code. Would that be 
acceptable?

Kind regards,
	Sebastian

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Re: timegm() and other time related functions

[R. Diez]

> while porting nats.c to RTEMS I noticed that Newlib doesn't provide a timegm() function.
> There a couple of related patches and discussions on the Newlib mailing list in the last years.

I tried to contribute an implementation of timegm() to Newlib a while ago, but after the reactions I got in this mailing list, I ended up contributing it to Picolibc instead. Search for timegm here:

https://github.com/picolibc/picolibc/blob/main/newlib/libc/time/mktime.c

This is the first commit:

https://github.com/picolibc/picolibc/commit/1a697a5228a04461066b851dfd96b1ddbbd603fa

And this commit adds the documentation for timegm:

https://github.com/picolibc/picolibc/commit/64d77e6dfefc4cdd40fda477d1d25f7a98d09c16

The affected files may have changed since them, so I would check the latest versions anyway.

I also contributed some tests for timegm. By the way, is the Newlib test suite still broken?

The timegm implementation actually needed little new code, it was basically a small reorganisation of existing Newlib code.

Regards,
   R. Diez