Programs across programming languages can make system calls. System calls can be a significant security concern. For example, allowing unsanitized user input is an obvious hazard.
A modern method of making system calls in C and C++ across operating systems is exec, known on Windows as _exec.
An execlp example demonstrates casting intptr_t to int for the specific cases where a function is known to use intptr_t in this way.
The Fortran 2003 standard ieee_arithmetic intrinsic module gives a robust standard way to use NaN and other functions. However, on certain CPU arches such as PPC, GCC does not yet support ieee_arithmetic.
An example of robust NaN is given in nans.f90. A Fortran standard way to make NaN constant is:
use, intrinsic :: ieee_arithmetic, only: ieee_value, ieee_quiet_nan
implicit none
real:: nan
nan = ieee_value(0., ieee_quiet_nan)Example NaN memory hex value–can be distinct on older/other compilers:
GCC 12.2.0; Intel oneAPI 2021, 2023
IEEE value isnan hex
real 32 NaN T 7FC00000
real 64 NaN T 7FF8000000000000
real128 NaN T 7FFF8000000000000000000000000000
complex 64 NaN T 7FC00000
complex128 NaN T 7FF8000000000000
complex256 NaN T 7FFF8000000000000000000000000000nvfortran 22.11 is same for real32/64
On Unix-like systems such as Linux and macOS, Python can detect if a script is being run as sudo / root from the UID, which is by definition zero for root.
import os
def running_as_root() -> bool:
return os.getuid() == 0or for demonstation as a one-liner:
python3 -c "import os; print(os.getuid() == 0)"When using an Apple Silicon CPU, it’s usually desirable to run the native version of the app rather than the Rosetta translated version for efficiency. If the app is live media based such as Zoom, using the native app version reduces CPU usage and helps avoid latency and jittering in the audio and video.
Determine if an app is native, Universal, or other architecture (Rosetta translated) by going to Applications in Finder. Highlight the application name and press โ I to see the “kind” of application. If the app is Universal, there will be a check box to force the app to run in Rosetta mode, which can be useful if an app has non-native plugins. Each application and its plugins must all be native or Rosetta.
To ensure created path names are compatible across computing platforms, it is useful to sanitize strings in general so that only alphanumeric characters are used to avoid adverse or accidental use of confusable UTF8 characters. In CMake this is accomplished like:
set(sneaky "โฒฃ๐๐
๐ฆ paly")
string(MAKE_C_IDENTIFIER ${sneaky} c)
message(NOTICE ${c})
# notice first characters and space are all underscoreSometimes in Git repositories with substantial amount of branches and history one may get a message on git switch like:
git switch develop1hint: If you meant to check out a remote tracking branch on, e.g. 'origin',
hint: you can do so by fully qualifying the name with the --track option:
hint:
hint: git checkout --track origin/<name>
hint:
hint: If you'd like to always have checkouts of an ambiguous <name> prefer
hint: one remote, e.g. the 'origin' remote, consider setting
hint: checkout.defaultRemote=origin in your config.
fatal: 'develop1' matched multiple (2) remote tracking branchesAs per that hint, this issue can be resolved by:
git config --global checkout.defaultRemote originmacOS Terminal works much like other operating systems, albeit with distinct keybindings from Linux et al.
Under Terminal โ Settings โ Profile โ Shell: “When the shell exists” pick “close if the shell exited cleanly”. This allows Control+D to exit Terminal like on Linux.
To set environment variables across Terminal sessions, put them in file ~/.zshrc. ~/.zshrc even works if one SSH’s into a macOS computer. A typical ~/.zshrc for developers might include:
export PS1="%1~ %# "This removes the name@machine to declutter the Terminal prompt.
export EDITOR=nanoThis sets the default text editor for many programs to nano, which makes operations easy for programs including Git
export CMAKE_GENERATOR=NinjaThis sets the default CMake generator to Ninja.
nullptr is a better defined replacement for NULL in the
C++11 standard
in header <cstddef> and in the
C23 standard
in header <stddef.h>.
Remember to include these system headers in source code to help compatibility across compilers–especially modern ones as internal includes are refined to have narrower include scope.
The basic structure for a rapidly updating animated plot with Matplotlib, without using
matplotlib.animation
is described below for imshow() and pcolormesh().
NOTE: matplotlib.pyplot.draw()
only takes effect on the CURRENT (most recently called) axes.
If updating multiple axes, call draw() after each set of axes is modified.
Both examples assume:
from matplotlib.pyplot import figure, draw, pause
# imgs is a N x X x Y image stack
fg = figure()
ax = fg.gca()If the pause() statement time is too small, Matplotlib may not update the plot at all.
Consider your display may not be able to update faster than about pause(0.01).
More examples with speed comparison showing that imshow is faster than pcolormesh generally.
imshow:
h = ax.imshow(imgs[0]) # set initial display dimensions
for img in imgs:
h.set_data(img)
draw(), pause(1e-3)pcolormesh:
h = ax.pcolormesh(imgs[0]) # set initial display dimensions
for img in imgs:
h.set_array(img.ravel())
draw(), pause(1e-3)Intel oneAPI 2023 provides GNU-like and MSVC-like compiler drivers for Windows. This is a good thing, but CMake had assumptions that only C++ compiler driver icpx OR icx would be present. CMake 3.25.2 fixed oneAPI 2023 compiler detection on Windows. Long term, GNU-like support for Windows may also come. Until you update CMake, you can workaround this issue of C++ oneAPI compiler detection on Windows by configuring the CMake project like:
cmake -Bbuild -DCMAKE_CXX_COMPILER=icx