Gerrit Proessl g3rrit

Debug with GDB on macOS 11

The big reason to do this is that LLDB has no ability to "follow-fork-mode child", in other words, a multi-process target that doesn't have a single-process mode (or, a bug that only manifests when in multi-process mode) is going to be difficult or impossible to debug, especially if you have to run the target over and over in order to make the bug manifest. If you have a repeatable bug, no big deal, break on the fork from the parent process and attach to the child in a second lldb instance. Otherwise, read on.

Install GDB

Don't make the mistake of thinking you can just brew install gdb. Currently this is version 10.2 and it's mostly broken, with at least two annoying bugs as of April 29th 2021, but the big one is https://sourceware.org/bugzilla/show_bug.cgi?id=24069

$ xcode-select install  # install the XCode command-line tools

Here's a list of mildly interesting things about the C language that I learned mostly by consuming Clang's ASTs. Although surprises are getting sparser, I might continue to update this document over time.

There are many more mildly interesting features of C++, but the language is literally known for being weird, whereas C is usually considered smaller and simpler, so this is (almost) only about C.

1. Combined type and variable/field declaration, inside a struct scope [https://godbolt.org/g/Rh94Go]

struct foo {
   struct bar {
 int x;

C++ `-std=...` default of various commonly used C++ compilers

Compiler	Version	`__cplusplus`
g++	4.7.4	199711L
	5.5.0	199711L
	6.1.0	201402L
	10.2	201402L
	11.1.0	201703L
clang++	3.4.2	199711L

	""""""""""""""""""""""
	" Leader
	""""""""""""""""""""""
	" let mapleader=,
	" can't set leaders in Obsidian vim, so the key just has to be used consistently.
	" However, it needs to be unmapped, to not trigger default behavior: https://github.com/esm7/obsidian-vimrc-support#some-help-with-binding-space-chords-doom-and-spacemacs-fans
	unmap ,

	" map ; to : in normal mode, so that I don’t rely on the shift key
	" nmap ; :


	#!/usr/bin/env sh

	# NOTE: First, have to ignore the following warnings to make it build on M1 Chip.
	#
	# -Wno-constant-logical-operand -Wno-format-nonliteral -Wno-self-assign
	#
	# To do so the above line should be appended to consts CFLAGS and CXXFLAGS
	# under the 'Programs producing files for the HOST machine' section of
	# the generated Makefile in dir 'build-gdb'.

	let s:second = 1
	let s:minute = 60 * s:second
	let s:hour = 60 * s:minute
	let s:day = 24 * s:hour
	let s:week = 7 * s:day
	let s:month = 30 * s:day
	let s:year = 365 * s:day

	function! s:get_undo_time(undo_dict) abort
	let l:idx = a:undo_dict.seq_cur

	<?php //encoding: utf-8
	$vocabulary = array(
	"a" =>"a!",// Ιͣ
	"akesi" =>"𖠊",//ꈡ𓆈𖧿
	"ala" =>"X",//╳ᳵ
	"alasa" =>"⨮",
	"ale" =>"⃛∞",//𑄗∾∞
	"ali" =>"∞",
	"anpa" =>"̣⊔",
	"ante" =>"≍",//ꇤ⪥⪤

	/* https://spectreattack.com/spectre.pdf */
	#include <stdio.h>
	#include <stdlib.h>
	#include <stdint.h>
	#ifdef _MSC_VER
	#include <intrin.h> /* for rdtscp and clflush */
	#pragma optimize("gt",on)
	#else
	#include <x86intrin.h> /* for rdtscp and clflush */
	#endif

	#!/bin/bash

	gdb -p "$1" -batch -ex 'set {short}$rip = 0x050f' -ex 'set $rax=231' -ex 'set $rdi=0' -ex 'cont'

	//DNS Query Program on Linux
	//Author : Silver Moon (m00n.silv3r@gmail.com)
	//Dated : 29/4/2009

	//Header Files
	#include<stdio.h> //printf
	#include<string.h> //strlen
	#include<stdlib.h> //malloc
	#include<sys/socket.h> //you know what this is for
	#include<arpa/inet.h> //inet_addr , inet_ntoa , ntohs etc

Gerrit Proessl g3rrit

Debug with GDB on macOS 11

Install GDB

1. Combined type and variable/field declaration, inside a struct scope [https://godbolt.org/g/Rh94Go]

C++ -std=... default of various commonly used C++ compilers

C++ `-std=...` default of various commonly used C++ compilers