pselect | Libreria javascript para rellenar selects / dropdowns html

When I was working on a TCP server running in a dedicated thread, I noticed strange behavior in signal handling. I have prepared the following MWE (I've used cerr to avoid race condition on debug printing):

I'm developing a program that needs to handle crash signals. By crash signal, I mean signals "delivered as a consequence of a hardware exception" [1], such as SIGFPE and SIGSEGV. I haven't found a specific name that describes this signal category, so I'm coming up with this one for clarity and less verbosity.

According to my research, catching these signals is a pain. A crash signal handler must not return, otherwise the behavior is undefined [2][3]. Having undefined behavior means an implementation may kill the process or re-raise the signal, leaving the program stuck in an infinite loop, which is not desirable.

On the other hand, there is little freedom inside signal handlers in general, specially in a multithreaded program: functions called within a signal handler must be both thread-safe and async-signal-safe [4]. For example, you may not call malloc() as it is not async-signal-safe, and neither can you call other functions that depend on it. In particular, as I'm using C++, I cannot make a safe call to GCC's abi::__cxa_demangle() to produce a decent stack trace because it uses malloc() internally. While I could use Chromium's library symbolize [5] for async-signal-safe and thread-safe C++ symbol name demangling, I could not use dladdr() for a more informative stack trace as it is not specified async-signal-safe.

An alternative approach for handling generic signals is blocking them in a worker thread with sigprocmask() (or pthread_sigmask() in a multithreaded program) and calling sigwait() in that thread. This works for non-crash signals such as SIGINT and SIGTERM. However, "if any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are generated while they are blocked, the result is undefined" [6], and again, all bets are off.

Skimming through the man pages of signal-safety [4], I found out that sem_post() is async-signal-safe (and thread-safe, of course) and implemented a solution around it which is similar to the sigwait() approach. The idea is to spawn a signal processing thread which blocks signals with pthread_sigmask() and calls sem_wait(). A crash signal handler is also defined such that whenever a crash signal is raised, the handler sets the signal to a global-scope variable, calls sem_post(), and waits until the signal processing thread finishes processing and exits the program.

Note that the following implementation does not check the return values from syscalls for the sake of simplicity.

i've just start a coding boot camp and for our third assignment we had to code a Random Password Generator with a few user preferences. i wrote my code and everything work apart from one bit. When the user only chooses to have numerical values an error is given where my selection pool of characters tells me that "pSelection.charAt is not a function at generatePWD".

It makes no sense to me at all considering that function works perfectly in every other situation. I've tried making a separate array for the specific (else if) Statement that is failing. I've tried swapping variable names in case of a clash of "Char".

If someone could have a look and tell me what I've done wrong i'd appreciate the help because i thought i understood what was going on but apparently not..

Here's the JavaScript - Below is the HTML

I am using UNIX domain datagram sockets to send records from multiple clients to a single server in a multithreaded program. Everything is done within one process; I'm sending records from multiple threads to a single thread that acts as the server. All threads are assigned to separate cores using their affinity masks.

It works fine with a single client, but now I am using multiple clients. The server will read data from the socket using select() to return file descriptors that are ready ("set"), then use recvfrom to get the records.

But first I need to write the file descriptors to the fd_set struct so I can use it with select(). I created fd_set as a global struct at the top of the C file that contains the programs to open client and server sockets and pass messages between them:

Is there a library that produces unified diff from two strings that diff2html can use? I've tried difflib but the output does not seem to fit the requirements that diff2html needs. I need a .js library I can import in the webpage to produce diffs between JSONs.

Tried to play around with the lineterm parameter but was not able to get the tool to work. If I use the string in the docs as an example, then it works:

I have a character vector and a data.tabe:

So, according to manual, pselect can have a timeout parameter and it will wait if no file-descriptors are changing. Also, it has an option to be interrupted by a signal:

I’m brand new to programming and I’m currently working on a MySQL database. I’m using Visual Studio Code for all of my JavaScript, HTML, and CSS files.

I have a JavaScript server file that is giving me issues. Our professor gave us his code for the server JavaScript file (which is posted below), his client JavaScript file (which is named contacts.js), and his HTML file.

He told us to open the server JavaScript file, open a terminal and type: node contacts.js. However, doing this gives me error messages that say that the document is not defined.

Occasionally, I'll even get "module not found" errors.

We just did a similar project last week and the terminal worked just fine with a similar node.js command, but I’m running into issues now and don’t know what to do. Hours on Google haven’t helped at all and my professor can’t be contacted for the entire week.

I’m not sure how to get beyond this “document not defined” error. Any help would be appreciated.

Below is the server JavaScript file:

This is definitely just a dumb misunderstanding on my part, but the man page for select() states:

The timeout argument specifies the interval that select() should block waiting for a file descriptor to become ready. The call will block until either:

*a file descriptor becomes ready;

*the call is interrupted by a signal handler; or

*the timeout expires.

And furthermore, that

On success, select() and pselect() return the number of file descriptors contained in the three returned descriptor sets (that is, the total number of bits that are set in readfds, writefds, exceptfds) which may be zero if the timeout expires before anything interesting happens. On error, -1 is returned, and errno is set to indicate the error; the file descriptor sets are unmodified, and timeout becomes undefined.

So my question is -- if it stops blocking as soon as a file descriptor is ready, would it not immediately return 1? And if no fds become ready, it returns 0, otherwise error and returns -1.

Obviously in practice it returns more than 1: the whole point is that you should be able to read/write multiple fds, right?