Get Matlab HTTP user agent, with this Matlab script.
Some servers may block Matlab download traffic such as websave(). A web browser from the same computer may work–this is a symptom of server user agent blocking. This script demonstrates setting a custom HTTP user agent using weboptions() to get around servers that block non-allow-listed user agents.
Python urllib.request can also set user agent.
Programs using HTTP typically report a user agent to avoid being blocked. User agent metadata help the server know user client statistics.
CMake’s HTTP user agent is like
curl/<curl version>as seen with CMake script.
Some servers may block CMake download traffic such as file(DOWNLOAD …). A web browser from the same computer may work–this is a symptom of server user agent blocking. This script demonstrates setting a custom HTTP user agent to get around servers that block non-allow-listed user agents.
PulseAudio is available via Homebrew.
brew install pulseaudioStart PulseAudio by:
brew services start pulseaudioCheck that PulseAudio is running by:
pactl list sinksThe proper “sink” may need to be selected to hear sound. Inspect the device list looking for say “Macbook Speakers” and set the default audio output device like:
pactl set-default-sink 1if “Sink #1” is the Macbook Speakers and so on.
Related: macOS X11
Python pathlib.Path.iterdir only iterates over a single directory level. It does not recurse directories.
A common task is to iterate over each subdirectory of a top-level directory non-recursively. Given directory structure:
a/b
z
y/1/2The Python iterdir example would return (in unspecified order):
a
z
yNotice in the C++ and Python examples, iterators are used that emit one element at a time rather than building up an entire list at once. Since directory operations are often unordered, there is no advantage to retrieving every directory name in a greedy operation rather than the lazy generators shown, particularly if networked file systems are being used.
The C11 standard defines optional bounds-checking functions with an “_s” suffix in their names in Annex K. There are numerous reasons why these functions aren’t implemented in popular compilers / stdlib except MSVC. The most salient points are in the field experience note that observes that static analysis, dynamic analysis, address sanitization, etc. provide benefits that are largely beyond what the secure functions could provide, without the end user runtime penalty.
For totally new projects, one could consider coding languages that have inherently more secure memory access such as Rust. Or for a less dramatic change, using C++ for string-heavy portions of the project where the string class can be easier to use than C char.
Major Git projects commonly have a workflow where other contributors fork a primary Git repository, make changes, and then contribute back to the primary project. This article describe the maintainer workflow. The contributor workflow is in a separate article.
This workflow is also suitable for projects using Git submodules, where you may want a submodule to temporarily use a branch from another repository.
Maintainers of a primary Git repo can make a local copy of the forked Git branch from the contributor’s Git repo to ensure the changes work as desired. Two ways for the maintainer to make this local copy are described in this article.
This workflow is suited to accommodate regular contributors to a project, for example colleagues or employees. In this example, we assume the primary project branch to merge new contributions into is “main” and that the remote contributor branch is “add-feat1”.
git remote add coworker-42 https://github.invalid/coworker-42/forked_project.git
git fetch coworker-42
git switch coworker-42/add-feat1Ensure that things work as desired. To merge the changes, do like:
git merge --no-ff add-feat1Check the Git history to verify the desired commits.
git logPush to the primary project as desired.
This workflow is suitable for occasional contributors. It avoids cluttering the local repo with many upstream repos metadata in .git/config.
On the local copy of the primary project, create a temporary branch in which to put the contributor’s remote branch. Here we assume the remote branch is “add-feat1”:
git switch -c contrib-add-feat1
git pull https://github.invalid/contrib/forked_project.git add-feat1After testing the new code to see that it’s suitable, merge the changes into the primary project:
git switch main
git merge --no-ff contrib-add-feat1Check the Git history to verify the desired commits.
git logPush to the primary project as desired. Finally, delete the temporary local branch:
git branch -d contrib-add-feat1CMake uses vendored libraries including cURL and nghttp2 to provide internet connectivity in CMake. As web technologies are created and obsolesced given the ubiquitous nature of HTTPS today, over various library versions, CMake version, and system configurations some failures may occur. To help catch these failures in new releases of CMake, as well as check connectivity on a particular platform and CMake version, try script check_https.cmake.
Public Git repos, GitHub Gists, and GitLab Snippets can use HTTPS for “git fetch”, “git pull”, and other Git download operations. Using HTTPS to download and verifying the author PGP signed Git commits can help assert that the content is from the intended authors. Git download operations over HTTPS are perhaps twice as fast as Git over SSH and use less CPU. By default, Git verifies SSL certs.
Typical Git hosting providers such as GitHub require SSH for enhanced security. Since “git push” operations typically take longer than “git pull”, particularly where pre-commit hooks and PGP commit signing are used, SSH speed penalty on “git push” is often acceptable.
For developers there are speed benefits from a hybrid Git configuration where Git downloads use HTTPS and Git uploads use SSH. Git has intrinsic functionality for this setup in a global configuration. The one-time setup below uses “https://” for the remote repo URL instead of “ssh://”. Replace “your_username” with your GitHub username for SSH GitHub Gists Git push.
git config --global url."ssh://github.com/".pushInsteadOf https://github.com/
git config --global url."ssh://gitlab.com/".pushInsteadOf https://gitlab.com/
git config --global url."ssh://gist.github.com/".pushInsteadOf https://gist.github.com/your_username/Note that GitLab Snippets doesn’t require an extra configuration setting like GitHub Gists does.
The file ~/.ssh/config is typically set for Git SSH keys.
This makes all
GitHub
and
GitLab
public repos push over SSH, unless overridden in a repo’s own Git config.
Confirm by git remote -v in a repo.
If experiencing problems on “git push”, check this matches the desired Git repo:
git config --get remote.origin.urlIn particular, it must NOT have a trailing slash like repo/
Major Git projects commonly have a contributor workflow where other contributors fork a primary Git repository, make changes, and then contribute back to the primary project. This article describe the contributor workflow. The maintainer workflow is in a separate article.
The contributor forks the primary project Git repo. On the local copy of the fork, create a feature branch:
git switch -c add-feature1Once the new work is complete, make the branch consistent with the primary repo by pulling in the latest changes from the primary repo:
git switch main
# whatever the primary or development branch of the primary repo is
git remote add upstream https://github.invalid/primary/repo_url
git fetch upstream
git rebase upstream/mainUpdate the local branch to remote main
git switch add-feature1
git rebase mainTest the final updated code. Create the Pull Request / Merge Request for the maintainer to evaluate the changes and possibly put them into the primary project.
OpenMPI 4.x uses temporary files for UNIX sockets, which are limited to 100 character path length. This can become an issue on macOS, which by default sets POSIX environment variable TMPDIR to a pseudorandom path under “/var” about 50 character long. We have experienced this as a race condition that becomes more likely as the number of MPI workers is eight or more.
A workaround is to set an alias for mpiexec or within CMake test properties etc. such that mpiexec gets a sufficiently short working path so that UNIX sockets don’t fail due to excessive path length.
CMake example