export fn _start() noreturn {
    assert(add(3, 4) == 7);
    assert(add(20, 10) == 30);

    exit();
}

fn add(a: u32, b: u32) u32 {
    var x: u32 = undefined;
    x = 0;
    x += a;
    x += b;
    return x;
}

pub fn assert(ok: bool) void {
    if (!ok) unreachable; // assertion failure
}

fn exit() noreturn {
    asm volatile ("syscall"
        :
        : [number] "{rax}" (231),
          [arg1] "{rdi}" (0)
        : "rcx", "r11", "memory"
    );
    unreachable;
}


[nix-shell:~/dev/zig/build-release]$ ./zig-cache/bin/zig build-exe test.zig 
[info] (compiler): Update completed in 0 ms

[nix-shell:~/dev/zig/build-release]$ objdump -d ./test -M intel

./test:     file format elf64-x86-64


Disassembly of section .text:

0000000008000000 <_start>:
 8000000:	55                   	push   rbp
 8000001:	48 89 e5             	mov    rbp,rsp
 8000004:	48 81 ec 00 00 00 00 	sub    rsp,0x0
 800000b:	bf 03 00 00 00       	mov    edi,0x3
 8000010:	be 04 00 00 00       	mov    esi,0x4
 8000015:	ff 14 25 10 00 00 04 	call   QWORD PTR ds:0x4000010
 800001c:	83 f8 07             	cmp    eax,0x7
 800001f:	48 0f 94 c7          	rex.W sete dil
 8000023:	ff 14 25 08 00 00 04 	call   QWORD PTR ds:0x4000008
 800002a:	bf 14 00 00 00       	mov    edi,0x14
 800002f:	be 0a 00 00 00       	mov    esi,0xa
 8000034:	ff 14 25 10 00 00 04 	call   QWORD PTR ds:0x4000010
 800003b:	83 f8 1e             	cmp    eax,0x1e
 800003e:	48 0f 94 c7          	rex.W sete dil
 8000042:	ff 14 25 08 00 00 04 	call   QWORD PTR ds:0x4000008
 8000049:	ff 14 25 18 00 00 04 	call   QWORD PTR ds:0x4000018
 8000050:	5d                   	pop    rbp
 8000051:	c3                   	ret    

000000000800006d <assert>:
 800006d:	55                   	push   rbp
 800006e:	48 89 e5             	mov    rbp,rsp
 8000071:	48 81 ec 00 00 00 00 	sub    rsp,0x0
 8000078:	83 f7 01             	xor    edi,0x1
 800007b:	48 f6 c7 01          	rex.W test dil,0x1
 800007f:	0f 84 01 00 00 00    	je     8000086 <assert+0x19>
 8000085:	cc                   	int3   
 8000086:	5d                   	pop    rbp
 8000087:	c3                   	ret    

0000000008000091 <add>:
 8000091:	55                   	push   rbp
 8000092:	48 89 e5             	mov    rbp,rsp
 8000095:	48 81 ec 10 00 00 00 	sub    rsp,0x10
 800009c:	c7 45 00 aa aa aa aa 	mov    DWORD PTR [rbp+0x0],0xaaaaaaaa
 80000a3:	c7 45 00 00 00 00 00 	mov    DWORD PTR [rbp+0x0],0x0
 80000aa:	8b 45 00             	mov    eax,DWORD PTR [rbp+0x0]
 80000ad:	01 f8                	add    eax,edi
 80000af:	89 45 00             	mov    DWORD PTR [rbp+0x0],eax
 80000b2:	8b 45 00             	mov    eax,DWORD PTR [rbp+0x0]
 80000b5:	01 f0                	add    eax,esi
 80000b7:	89 45 00             	mov    DWORD PTR [rbp+0x0],eax
 80000ba:	8b 45 00             	mov    eax,DWORD PTR [rbp+0x0]
 80000bd:	48 83 c4 10          	add    rsp,0x10
 80000c1:	5d                   	pop    rbp
 80000c2:	c3                   	ret    

00000000080000d3 <exit>:
 80000d3:	55                   	push   rbp
 80000d4:	48 89 e5             	mov    rbp,rsp
 80000d7:	48 81 ec 00 00 00 00 	sub    rsp,0x0
 80000de:	b8 e7 00 00 00       	mov    eax,0xe7
 80000e3:	31 ff                	xor    edi,edi
 80000e5:	0f 05                	syscall 
 80000e7:	cc                   	int3   
 80000e8:	5d                   	pop    rbp
 80000e9:	c3                   	ret    

00000000080000f1 <exit__anon_0>:
 80000f1:	7b 72 61 78 7d 00 72 64                             {rax}.rd

00000000080000f9 <exit__anon_1>:
 80000f9:	7b 72 64 69 7d 00 79 73                             {rdi}.ys

0000000008000101 <exit__anon_2>:
 8000101:	73 79 73 63 61 6c 6c 00                             syscall.