Re: Gawk strftime problem under MacOS Ventura using %z format with utc-flag set

[arnold]

Hello.

Thank you for the report.

This looks to be a problem in the C library version of strftime on
MacOS, as that is what gawk is calling.  You can validate this by
writing a C program to call strftime directly and see if you get the
same results.

There isn't anything gawk can do about this. However, you can try
the following:

1. Start over with a clean extraction of the gawk source code tar ball.
2. Run configure.
3. Edit the generated config.h and use

        #undef HAVE_STRFTIME

instead of

        #define HAVE_STRFTIME 1

4. Run make make
5. Rerun your test script with the new version of gawk.

By undefining HAVE_STRFTIME, gawk will be built with an early version of
strftime.c from the GNU C library that may work better.

I hope this helps,

Arnold

Stuart Ferguson <stuart.fergs@gmail.com> wrote:

> Attestation 1:
>
> I have read https://www.gnu.org/software/gawk/manual/html_node/Bugs.html
> -- Yes.
>
> Attestation 2:
>
> I have not modified the sources before building gawk.
> -- True.
>
> Description:
>
> I ran the following script under a number of different operating systems:
>
> BEGIN {
>   unixTime = 1687531200
>   split("America/Chicago Europe/Berlin Asia/Kolkata", tz)
>
>   for (str in tz) {
>     ENVIRON["TZ"] = tz[str]
>     for (utcFlag = 0; utcFlag <= 1; utcFlag++) {
>       print strftime("%F %T %Z %z", unixTime, utcFlag), utcFlag
>     }
>   }
> }
>
> Under MacOS Ventura (Test case 1, below), the strftime %z output appears to
> be
> incorrect when utc-flag (using Gawk manual terminology) is set. Notice the
> discrepancy: %Z output is "UTC", but %z is NOT "+0000".
>
> What appears to be happening is that utc-flag is altering the %z output for
> daylight saving time, not setting %z output to "+0000". I have confirmed
> this
> outcome (not documented here) by running the script with a Unix time
> corresponding to winter in the Northern hemisphere, when DST is not in
> effect.
>
> Running the script under Ubuntu 23.04 (Test case 2) and Alpine Linux 3.18
> (Test case 3) does not exhibit the same problem. In each case, %Z output of
> "UTC" or "GMT" corresponds to %z output of "+0000".
>
> I'm afraid I don't have a suggestion to fix the problem. Nevertheless, I
> hope
> this bug report is useful.
>
> Stuart
>
> ---------------------------------------
>
> Test case 1: MacOS Ventura 13.4.1
>
> Configuration Information ---
> Machine: aarch64
> OS: darwin22.4.0
> Compiler: clang
> Compilation CFLAGS: -g -O2 -DNDEBUG
> uname output: Darwin Stuarts-MacBook-Air.local 22.5.0 Darwin Kernel Version
> 22.5.0: Thu Jun  8 22:22:19 PDT 2023;
> root:xnu-8796.121.3~7/RELEASE_ARM64_T8103 arm64
> Machine Type: aarch64-apple-darwin22.4.0
> Gawk Version: 5.2.2
>
> Script output ---
> 2023-06-23 09:40:00 CDT -0500 0
> 2023-06-23 14:40:00 UTC -0600 1
> 2023-06-23 16:40:00 CEST +0200 0
> 2023-06-23 14:40:00 UTC +0100 1
> 2023-06-23 20:10:00 IST +0530 0
> 2023-06-23 14:40:00 UTC +0530 1
>
> ---------------------------------------
>
> Test case 2: Ubuntu 23.04
>
> Configuration Information ---
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -g -O2 -ffile-prefix-map=/build/gawk-eXJnST/gawk-5.2.1=.
> -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat
> -Werror=format-security
> -fdebug-prefix-map=/build/gawk-eXJnST/gawk-5.2.1=/usr/src/gawk-1:5.2.1-2
> -DNDEBUG
> uname output: Linux Pk2 6.2.0-20-generic #20-Ubuntu SMP PREEMPT_DYNAMIC Thu
> Apr 6 07:48:48 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
> Gawk Version: 5.2.1
>
> Script output ---
> 2023-06-23 09:40:00 CDT -0500 0
> 2023-06-23 14:40:00 GMT +0000 1
> 2023-06-23 16:40:00 CEST +0200 0
> 2023-06-23 14:40:00 GMT +0000 1
> 2023-06-23 20:10:00 IST +0530 0
> 2023-06-23 14:40:00 GMT +0000 1
>
> ---------------------------------------
>
> Test case 3: Alpine Linux 3.18
>
> Configuration Information ---
> Machine: i586
> OS: linux-musl
> Compiler: gcc
> Compilation CFLAGS: -Os -Wformat -Werror=format-security -flto=auto -DNDEBUG
> uname output: Linux Stuarts-iPhone-2 4.20.69-ish SUPER AWESOME May 20 2023
> 23:41:32 i686 Linux
> Machine Type: i586-alpine-linux-musl
> Gawk Version: 5.2.2
>
> Script output ---
> 2023-06-23 09:40:00 CDT -0500 0
> 2023-06-23 14:40:00 UTC +0000 1
> 2023-06-23 16:40:00 CEST +0200 0
> 2023-06-23 14:40:00 UTC +0000 1
> 2023-06-23 20:10:00 IST +0530 0
> 2023-06-23 14:40:00 UTC +0000 1