Category: Code

X11 / xserver / XWIN gvim problems

GullRaDriel

Case:

WARNING**: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files

Solved by adding NO_AT_BRIDGE=1 before launching gvim ( i.e [user@server]$ NO_AT_BRIDGE=1 gvim myfile.txt) source: https://github.com/NixOS/nixpkgs/issues/16327

Case:

connect /tmp/.X11-unix/X0: Permission denied
E233: cannot open display
Press ENTER or type command to continue

Solved by using correct DISPLAY informations before connecting (DISPLAY=localhost:0.0) source: https://unix.stackexchange.com/a/220234

execve: no such file or directory

GullRaDriel

If one day when using execve you encounter the “no such file or directory” problem, and that the file you tried to launch is really existing and with the good rights, then the problem is coming from the shebang not pointing to a valid interpreter.

In example: #!/bin/ksh and ksh is not installed

#reminder #execve

Easier pthread mutex deadlock detection

GullRaDriel

Thread programming is fun, starting a tons of process and syncing them on a task, or asynchronously process a bunch of data. But that fun is having a cost: data sharing have to be somewhat locked or well ordered when accessing it. Else you’re going to face some seriously strange situations like time warping variables at the best and big crashes at worse.

On top of that let’s add that the main tools to protect our datas reads / writes by threads can also lead to strange situations where only parts of the code is still running and the rest is in “deadlock” state.

On little examples detecting those deadlocks seems easy, but when scaled to a bigger project/api, it’s a living hell.
Tools like valgrind may detect the problems at the cost of big performance loss which may lead to being unable to run into the problem before running into the machine limits.

I was searching for a good ressource to help me in my debugging quest when I stumbled upon that article from Aurelian Melinte which I think is very good (both the author and article): https://linuxgazette.net/150/melinte.html that provide some code samples to superseed the pthread functions with some that will make some checks during the calls.

There is also the gdb deadlock detector script by DamZiobro : https://github.com/DamZiobro/gdb-automatic-deadlock-detector

And finally valgrind- helgrind: http://valgrind.org/docs/manual/hg-manual.html

Now back to code and monitoring/debugging !



Cross platform correct socket error code

GullRaDriel

A friend using my networking code made the good point that it was not correctly reporting errors on some windows compilers.

I hope we got this sorted out.

Grab / update your code from the git repo: https://framagit.org/GullRaDriel/nilorea-library

Added:
-netw_unload() =>macro who calls WSACleanup . Call it before exiting (on OK or error). Does nothing on *nix/*nux


-netw_set_blocking(…) => set blocking mode on a network

Internals:
-neterr => WSAGetLastError or errno
-netstrerr => FormatMessage or strerror (strerror_r wrapper is quoted because not working on redhat)

This has caused a full revamping of all error management, but now it’s ok. Valgrind checked.

#nilorea-library #networking #winsock #socket

Micro$oft and sockets

GullRaDriel

Microsoft, have you ever done something as bad as your pesky winsock wrapper around classic sockets ? (correct Berkeley’s error code support for FTW)And your way of always reinventing the wheel at your sauce is FUCKING BORING (Hell yeah, why just use open source? Let’s just add a bunch of proprietary shit inside ==> all those boring WINAPIs which are BTW NOT PORTABLE).

It’s BOOOORING, booooring , booooooooring. (Did I add enough ‘o’ ? Because I think you didn’t add enough WSAshit everywhere)

Now I have to make a proper wrapper because you, as a big company, are not able to follow the standards and make things simple and portable. Micro$oft.

From MSDN: “This means, for example, that checking for errors when the socket and accept functions return should not be done by comparing the return value with –1, or seeing if the value is negative (both common and legal approaches in UNIX). Instead, an application should use the manifest constant INVALID_SOCKET as defined in the Winsock2.h header file.”

Hell yeah, let’s review all our calls to check for a specific Windows code….#ShitNumber1

Also: WSAGetLastError() == WSAEWOULDBLOCK , yeah, yeah, why just use common naming convention when you can add WSAshit everywhere ?

Lets not just talk about the FormatMessage function. Using strerror would have been too much for you to handle, it’s a single line func with a single parameter.

#Bored#GrumpyCoder#Microsoft#Windows#Winsock#API#WSAshitFunctions