From 9900f94afe5556db048b4b147bbf75ff0e0c9974 Mon Sep 17 00:00:00 2001
From: Marcio Giaxa <i@mgxm.me>
Date: Tue, 18 Dec 2018 16:22:20 -0200
Subject: [PATCH] freebsd: use sysctl to get the current executable path

FreeBSD doesn't mount procfs as default on the base system, so we can't
depend on it to get the current path, In this case, we use sysctl(3) to
retrieves the system information and get the same information.

 - CTL_KERN: High kernel limits

 - KERN_PROC: Return selected information about specific running
   processes.

 - KERN_PROC_PATHNAME: The path of the process

 - Process ID: a process ID of -1 implies the current process.
---
 std/os/freebsd/index.zig |  6 ++++++
 std/os/index.zig         | 15 ++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/std/os/freebsd/index.zig b/std/os/freebsd/index.zig
index 9f9f7f9de0..47f4e8e267 100644
--- a/std/os/freebsd/index.zig
+++ b/std/os/freebsd/index.zig
@@ -9,6 +9,12 @@ const assert = std.debug.assert;
 const maxInt = std.math.maxInt;
 pub const Kevent = c.Kevent;
 
+pub const CTL_KERN = 1;
+pub const CTL_DEBUG = 5;
+
+pub const KERN_PROC = 14; // struct: process entries
+pub const KERN_PROC_PATHNAME = 12; // path to executable
+
 pub const PATH_MAX = 1024;
 
 pub const STDIN_FILENO = 0;
diff --git a/std/os/index.zig b/std/os/index.zig
index b49b46e8e5..817f11493c 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -2291,7 +2291,20 @@ pub fn selfExePathW(out_buffer: *[windows_util.PATH_MAX_WIDE]u16) ![]u16 {
 pub fn selfExePath(out_buffer: *[MAX_PATH_BYTES]u8) ![]u8 {
     switch (builtin.os) {
         Os.linux => return readLink(out_buffer, "/proc/self/exe"),
-        Os.freebsd => return readLink(out_buffer, "/proc/curproc/file"),
+        Os.freebsd => {
+            var mib = [4]c_int{ posix.CTL_KERN, posix.KERN_PROC, posix.KERN_PROC_PATHNAME, -1};
+            var out_len: usize = out_buffer.len;
+            const err = posix.getErrno(posix.sysctl(&mib, 4, out_buffer, &out_len, null, 0));
+
+            if (err == 0 ) return mem.toSlice(u8, out_buffer);
+
+            return switch (err) {
+                posix.EFAULT => error.BadAdress,
+                posix.EPERM => error.PermissionDenied,
+                else => unexpectedErrorPosix(err),
+            };
+
+        },
         Os.windows => {
             var utf16le_buf: [windows_util.PATH_MAX_WIDE]u16 = undefined;
             const utf16le_slice = try selfExePathW(&utf16le_buf);