andrewrk

const std = @import("std");

// leak
test "example 1" {
    var array = std.ArrayList(i32).init(std.testing.allocator);

    try array.append(1234);
}

// double free

andrewrk

; Function Attrs: nobuiltin noredzone nounwind sspstrong
define void @entry() #1 !dbg !2228 {
Entry:
  %0 = alloca %Foo, align 4
  call fastcc void @doit(%Foo* sret %0), !dbg !2232
  ret void, !dbg !2234
}

; Function Attrs: nobuiltin noredzone nounwind sspstrong
define internal fastcc void @doit(%Foo* nonnull sret %0) unnamed_addr #1 !dbg !2235 {

andrewrk

usingnamespace @import("std").builtin;
/// Deprecated
pub const arch = Target.current.cpu.arch;
/// Deprecated
pub const endian = Target.current.cpu.arch.endian();

/// Zig version. When writing code that supports multiple versions of Zig, prefer
/// feature detection (i.e. with `@hasDecl` or `@hasField`) over version checks.
pub const zig_version = try @import("std").SemanticVersion.parse("0.8.0-dev.1159+d9e46dcee");

andrewrk

#include <stdbool.h>
#include <stddef.h>

void __attribute__((weak)) dlopen(const char *filename, int flags);
int __attribute__((weak)) dlclose(void *handle);

struct ZigWindowFns {
    void (*dlopen)(const char *filename, int flags);
    int (*dlclose)(void *handle);
};

andrewrk

Absolute Zero

Bootstrapping Zig from below C level.

Motivation

The first computer programs were written directly in machine code. To make things easier, automated assemblers were developed, initially in machine code as well and then in their own input language. To make things easier again, high-level (for the time) languages such as BCPL, B, and eventually C were developed, which abstracted some of the details of the underlying architecture and allowed more complex compound logic. These languages were implemented by first writing compilers for subsets of them in assembly, then using those compilers to compile compilers for the full languages. Thus, there was a concrete bootstrap chain extending right down to assembly.

Nowadays, this is a lost art. Quite literally all languages that bootstrap themselves nowadays start from a pre-existing high-level language, usually C or C++, and then reject their roots as soon as they can. Zig stands out by maintaining its bootstrap chain, but this chain begins at a sy

andrewrk

andy@ark ~/tmp> gcc -o hello hello.c
andy@ark ~/tmp> strace ./hello
execve("./hello", ["./hello"], 0x7ffe96b5ddb0 /* 62 vars */) = 0
brk(NULL)                               = 0x2129000
access("/etc/ld-nix.so.preload", R_OK)  = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/tls/haswell/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/tls/haswell/x86_64", 0x7fff2bd55cc0) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/tls/haswell/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/tls/haswell", 0x7fff2bd55cc0) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/tls/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or dire

andrewrk

[nix-shell:~/Downloads/zig/build-memprof]$ /home/andy/Downloads/zig/build-memprof/zig build-exe /home/andy/Downloads/zig/src-self-hosted/main.zig --pkg-begin build_options /home/andy/Downloads/zig/zig-cache/zig_build_options.zig --pkg-end --cache-dir /home/andy/Downloads/zig/zig-cache --name zig --cache on -fmem-report
LLVM Emit Output...
--- MEMORY PROFILE REPORT [ArenaAllocator]: pass1 ---
  ZigValue: 88 bytes each, alloc{ 11598748 calls, 12201639 objects, total 1.000 GiB }, dealloc{ 0 calls, 0 objects, total 0.000 bytes }, remain{ 11598748 calls, 12201639 objects, total 1.000 GiB }

  Total bytes allocated: 1.000 GiB, deallocated: 0.000 bytes, remaining: 1.000 GiB
  Total calls alloc: 11598748, dealloc: 0, remain: 11598748
/home/andy/Downloads/zig/zig-cache/o/otcooWOP9TnG_gnFACLXE_743NOny6YBSAPQTDX5Rd7qC2swx_yDtkMjVzxxqjWB

--- IR INTERNING REPORT ---

andrewrk

@noreturn = primitive(noreturn)
@void = primitive(void)
@usize = primitive(usize)
@0 = int(0)
@1 = int(1)
@2 = int(2)
@3 = int(3)

@syscall_array = str("syscall")
@sysoutreg_array = str("={rax}")

andrewrk

test "benchmark" {
    var timer = try std.time.Timer.start();
    const start = timer.lap();
    var i: usize = 0;
    var hash: usize = 0;
    while (i < 1000000) : (i += 1) {
        const src = "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.";
        var output: [100]u8 = undefined;
        var bf: BrainFuckInterpreter = undefined;
        bf.init(src, "", &output, 500);

andrewrk

fn entry(start_index: usize, slice: []usize, value: usize) ?usize {
    var i: usize = start_index;

    while (i >= 0) : (i -= 1) {
        if (slice[i] == value) {
            return i;
        }
    }

    return null;