x-yuri

git: branch.autoSetupMerge

branch.autoSetupMerge makes git branch, git switch and git checkout set upstream for branches they create:

• false - no upstream is set

• simple - upstream is set to <start-point> when <start-point> is a remote-tracking branch and the branch names (the one to be created and the remote one) match

  On a side note, one can't create a local branch, which name matches the name of another local branch, as such one might say that if the branch names match, <start-point> can't be a local branch, i.e. <start-point> is a remote-tracking branch.

x-yuri

bats

a.bats:

strict() { set -euo pipefail; shopt -s inherit_errexit; "$@"; }

setup() {
    [ "$BATS_LIB_PATH" = /usr/lib/bats ] && BATS_LIB_PATH=$HOME/.bats/lib:$BATS_LIB_PATH
    bats_load_library bats-support

x-yuri

bash: arrays and set -u

In bash < 4.4 "${a[@]}" fails (unbound variable) if a is unset (nothing was assigned to a) or a=(). Also "${a[@]:+${a[@]}}" and "${a[@]+${a[@]}}" produce empty arrays if a=('').

What works before, after and in 4.4 is ${a[*]+"${a[@]}"} and ${a[@]+"${a[@]}"}.

It should also be mentioned that ${#a[@]} fails if a is unset (regardless of the version). And ${a[i]} fails if the specified element doesn't exist.

a.bats:

x-yuri

bash: word splitting

Word Splitting
IFS=, read -ra fields <<< "$csv_line"

a.bats:

setup() {
 [ "$BATS_LIB_PATH" = /usr/lib/bats ] && BATS_LIB_PATH=~/.bats/lib:$BATS_LIB_PATH

x-yuri

gcloud functions deploy: .gcloudignore

(the beginning)

The algorithm is basically as follows:

for each dir:
  if allowed:
    for each file (of this dir):

x-yuri

perl: internal representation of numbers

Perl can internally represent numbers in 3 different ways: as native integers, as native floating point numbers, and as decimal strings.

https://perldoc.perl.org/perlnumber

Small integer numbers are stored as signed integers. When that is not possible perl switches to unsigned integers. And then to floating point numbers:

a.pl:

x-yuri

perl: pack()

I'm going to ignore the j, J, f, F, d, D, p, P, u, w formats.

My machine has the x86_64 architecture (little-endian) and I'm running perl-5.38-2.

The way it's described is not necessarily matches the way it works internally. This is merely an explanation that seems to work.

$ perl -V:shortsize -V:intsize -V:longsize -V:longlongsize

x-yuri

Building mecab (with its perl module) with debug symbols

Dockerfile:

FROM alpine:3.20.3
RUN set -x && apk add git build-base autoconf gdb automake libtool gettext-dev perl-dev \
    && git clone https://github.com/taku910/mecab \
    && cd mecab \
    && git checkout 05481e751dd5aa536a2bace46715ce54568b972a \

x-yuri

Creating a shared library in C/C++

a.c:

#include <stdio.h>
#include "a.h"

void f(void)
{

x-yuri

Making a STUN request in C

a.c:

#include <stdlib.h>
#include <sys/socket.h>
#include <err.h>
#include <stdio.h>
#include <sys/random.h>