Matthew Cole colematt

Connecting to Remote by SSH

Virtual Private Network (VPN)
- Windows
- MacOS
- Linux
Secure Shell (SSH) Client
- Windows

How to generate an LLVM docset for Dash

Prerequisites

brew install swiftdocorg/formulae/docsetutil
sudo ln -s /usr/local/bin/docsetutil /Library/Developer/CommandLineTools/usr/bin/docsetutil
brew install doxygen graphviz

export PROJ_ROOT=$(pwd)
mkdir -p llvm && cd llvm

# Using Ubuntu 18.04 Prebuild Toolchain from https://releases.llvm.org/download.html
wget https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/clang+llvm-10.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz \
     https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/clang+llvm-10.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz.sig \
     https://releases.llvm.org/10.0.0/hans-gpg-key.asc
gpg --import hans-gpg-key.asc
gpg --verify clang+llvm-10.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz.sig clang+llvm-10.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz

Get elements from a multi-dimensional array

import functools
import operator
def arrget(array,tup):
	'''
	Given a tuple containing the dimensional indices, retrieve that element from a multi-dimensional array
	'''
	return functools.reduce(lambda arr, idx: operator.getitem(arr,idx), tup, array)

Allocating Multi-dimensional Arrays in C

This gist was inspired by the Geeks for Geeks' writeup How to dynamically allocate a 2D array in C? by Abhay Rathi. It has been formatted to remove interstitial ads, provide a fixed URL for links, and to modify the problem statement to match that which is commonly used in Hackerrank/Grind75/LeetCode/ACM problems where the input must be read from standard input.

Problem

We want to read input from standard input, where the nature of the input is as follows:

On line 1, $R$: the number of rows, and $C$: the number of columns in a 2D array, space-separated and newline-terminated.
On lines 2 through $R+1$, the row's columns, space-separated and newline-terminated.

Where does the C/C++ Compiler Find Header Files?

Ask the Preprocessor

GNU

# GNU C++ preprocessor
`gcc -print-prog-name=cc1plus` -v
# GNU C preprocessor

Adding Programs and System Calls to XV6

Adding Userspace programs

To add a userspace program that can be executed in xv6 shell, make the following additions/edits:

program.c

Include the headers needed to gain access to system call wrapper prototypes: types.h, user.h.
If you need access to struct stat, include its header: stat.h

	#include <locale.h>
	#include <stdio.h>
	#include <wchar.h>

	/* REFERENCES
	* Control Block: http://unicode.org/charts/PDF/U0000.pdf
	* Control Pictures: http://unicode.org/charts/PDF/U2400.pdf
	*/

	int main(int argc, char* argv[]) {

	CFLAGS=-g -Wall -std=c99
	LDFLAGS=
	LDLIBS=-lcunit
	RMFLAGS=-f

	all: basic

	.PHONY: clean
	clean:
	$(RM) $(RMFLAGS) basic

	#include <stdint.h> // uint64_t
	#include <stdio.h> // printf

	uint64_t twiddle(uint64_t x) {
	uint64_t smallest, ripple, new_smallest, ones;

	if (x == 0)
	return 0;
	smallest = (x & -x);
	ripple = x + smallest;