zig build hangs on faccessat sycall

[komuw]

zig version

0.6.0+b0684bf08

uname -ra

Darwin Kernel Version 19.6.0:  root:xnu-6153.141.1~1/RELEASE_X86_64 x86_64

I created this file

const std = @import("std");
const warn = @import("std").debug.warn;

pub fn main() void {
    warn("hello world\n", .{});
}

When I run it, it works okay;
zig run main.zig

hello world

However when I build it, it 'hangs'
zig build main.zig

ps aux | grep -i zig

95060 /usr/local/zig/zig build main.zig

sudo dtruss -acefl -p 95060

95060/0x833fe0:  83180607       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180608       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180610       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180611       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180612       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180613       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180614       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180615       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180616       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180617       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180619       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180620       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180621       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180622       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180623       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180624       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180625       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180626       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180627       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180628       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180630       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180631       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180632       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180633       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180634       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180635       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2
95060/0x833fe0:  83180636       3      0 faccessat(0xFFFFFFFFFFFFFFFE, "/build.zig\0", 0x0, 0x0)         = -1 2

I do not have a build.zig in the my directory, the only thing I have is main.zig.
I'm guessing that the build.zig file in question is a default one maybe somewhere in the compiler/stdlib??
But I would expect zig to fail with an error if it is unable to faccessat it rather than loop on that syscall.

[komuw]

Interesting, if I remove the main.zig file, so that I'm left with an empty directory; and then I re-run
/usr/local/zig/zig build main.zig the issue still happens

[Tetralux]

zig build is not valid with a explicit file, and is completely seperate from zig build-exe file.zig, which is I suspect what you intended.

However you should get an error that build.zig does not exist in the current directory, rather than a hang.

[LemonBoy]

Looks suspiciously similar to #6584, the traversal reaches the root and then hangs forever.
Yes, it's the same fucking dirname shit again.

[andrewrk]

0.7.0 milestone, call me out if I try to post-pone this issue :-)