patshaughnessy

This note explains how to build Postgres from source and setup to debug it using LLDB on a Mac. I used this technique to research this article:
http://patshaughnessy.net/2014/10/13/following-a-select-statement-through-postgres-internals

1. Shut down existing postgres if necessary - you don’t want to mess up your existing DB or work :)

$ ps aux | grep postgres
pat               456   0.0  0.0  2503812    828   ??  Ss   Sun10AM   0:11.59 postgres: stats collector process       
pat               455   0.0  0.0  2649692   2536   ??  Ss   Sun10AM   0:05.00 postgres: autovacuum launcher process       
pat               454   0.0  0.0  2640476    304   ??  Ss   Sun10AM   0:00.74 postgres: wal writer process       
pat               453   0.0  0.0  2640476    336   ??  Ss   Sun10AM   0:00.76 postgres: writer process       

patshaughnessy

// Code from: http://patshaughnessy.net/2020/1/20/downloading-100000-files-using-async-rust
//
// Cargo.toml:
// [dependencies]
// tokio = { version = "0.2", features = ["full"] }
// reqwest = { version = "0.10", features = ["json"] }
// futures = "0.3"

use std::io::prelude::*;
use std::fs::File;

patshaughnessy

* 
 * application.css.less
 *= require_self
*/  

@import "twitter/bootstrap/reset.less";

@import "twitter/bootstrap/variables.less";

// Override link color for my app:

patshaughnessy

Recently someone asked me for online resources about MRI's internal C source
code. Here are a few - if there are more to add please leave a comment! - pat

1. Ruby Hacking Guide - The definitive resource for people who want to learn
the C programming details of how Ruby works internally. Intended for C hackers.
It was just recently translated into English from the original Japanese.
http://ruby-hacking-guide.github.io

2. Various presentations by Koichi Sasada - he often does public presentations
on Ruby internals and they're always fascinating and full of technical details.

patshaughnessy

fn main() {
    let needle = "list".to_string();
    let haystack = ["some".to_string(), "long".to_string(), "list".to_string(), "of".to_string(), "strings".to_string()].to_vec();

    if let Some(str) = haystack.iter().find(|&s| *s == needle) {
        println!("{}", needle);
    } else {
        println!("Nothing there...");
    }
}

patshaughnessy

#[macro_use]
extern crate diesel;

use diesel::prelude::*;

table! {
    users (id) {
        id -> Int4,
        first_name -> Nullable<Varchar>,
        last_name -> Nullable<Varchar>,

patshaughnessy

Hi guys, So in episode 7 you were asking about where and how the puts method connects to the computer’s display and writes the output. And in episode 8 you were asking about the times method, how that worked and why it wasn’t implemented with YARV instructions. In both cases, I didn’t go into detail about this in the book because it would have distracted you from the topic at hand, which is how YARV executes your code. (Or in this case, my example Ruby code from the book.)

Both the puts and times methods were written by the Ruby code team, and not by you or me. Both of them are implemented in C code. So when you’re writing a Ruby program, some of the methods you write yourself, but you get many other methods for free because they are part of the Ruby language. Many of the these built in methods are part of the standard library, which means they are Ruby code written by the Ruby core team, while other built in methods are written directly in C code by the Ruby team.

As you know, the puts method tak

patshaughnessy

/* 
 * application.css.scss
 *= require_self
*/  

@import "bootstrap/reset.css.scss";

@import "bootstrap/variables.css.scss";

// Override link color for my app:

patshaughnessy

# Prepare a new stack frame (save the old base pointer, and set
the new base pointer to the current stack pointer)
pushq %rbp
movq %rsp, %rbp

# Get the address of your string (lea = load effective address)
# and put it into the rdi register as a parameter to printf.
leaq L_.str(%rip), %rdi

# Not sure why this is needed - I believe it sets eax to zero.

patshaughnessy

-- Change RTEST:

//#define RTEST(v) !(((VALUE)(v) & ~Qnil) == 0)
#define RTEST(v) ((VALUE)(v) != Qnil && (VALUE)(v))

-- Recompile with -S flag:

clang -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Werror=pointer-arith -Werror=write-strings -Werror=declaration-after-statement -Werror=shorten-64-to-32 -Werror=implicit-function-declaration -Werror=division-by-zero -Werror=extra-tokens -pipe -D_FORTIFY_SOURCE=2 -fstack-protector -fno-strict-overflow -fvisibility=hidden -DRUBY_EXPORT -fPIE -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT -I. -I.ext/include/x86_64-darwin12.0 -I./include -I. -S -o object.o -c object.c

-- And here's the new assembly language - it's longer with a condition in the middle (See: je	LBB7_2)