From 50a2bb58d23a686f52b389c062f0299cc2a5f8ed Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Fri, 14 Jan 2022 18:04:11 -0700
Subject: [PATCH] link: PTRACE_ATTACH/PTRACE_DETACH

---
 src/link.zig | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/link.zig b/src/link.zig
index 34a16a1a1b..a2f40eed65 100644
--- a/src/link.zig
+++ b/src/link.zig
@@ -378,7 +378,7 @@ pub const File = struct {
                 if (build_options.only_c) unreachable;
                 if (base.file != null) return;
                 const emit = base.options.emit orelse return;
-                if (base.child_pid != null) {
+                if (base.child_pid) |pid| {
                     // If we try to open the output file in write mode while it is running,
                     // it will return ETXTBSY. So instead, we copy the file, atomically rename it
                     // over top of the exe path, and then proceed normally. This changes the inode,
@@ -388,6 +388,11 @@ pub const File = struct {
                     });
                     try emit.directory.handle.copyFile(emit.sub_path, emit.directory.handle, tmp_sub_path, .{});
                     try emit.directory.handle.rename(tmp_sub_path, emit.sub_path);
+
+                    switch (std.os.errno(std.os.linux.ptrace(std.os.linux.PTRACE.ATTACH, pid, 0, 0, 0))) {
+                        .SUCCESS => {},
+                        else => |errno| log.warn("ptrace failure: {s}", .{@tagName(errno)}),
+                    }
                 }
                 base.file = try emit.directory.handle.createFile(emit.sub_path, .{
                     .truncate = false,
@@ -437,6 +442,13 @@ pub const File = struct {
                 }
                 f.close();
                 base.file = null;
+
+                if (base.child_pid) |pid| {
+                    switch (std.os.errno(std.os.linux.ptrace(std.os.linux.PTRACE.DETACH, pid, 0, 0, 0))) {
+                        .SUCCESS => {},
+                        else => |errno| log.warn("ptrace failure: {s}", .{@tagName(errno)}),
+                    }
+                }
             },
             .c, .spirv, .nvptx => {},
         }