From 6d47198303847409a900f57bbe84195b32375093 Mon Sep 17 00:00:00 2001
From: Ben Crist <ben@magicmoremagic.com>
Date: Sun, 20 Nov 2022 12:20:14 -0600
Subject: [PATCH 1/2] return error.AlreadyTerminated from std.ChildProcess.kill
 when necessary

---
 lib/std/child_process.zig | 10 ++++++++--
 lib/std/os.zig            |  4 ++--
 lib/std/os/windows.zig    |  3 ++-
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/lib/std/child_process.zig b/lib/std/child_process.zig
index 6a5fabc41f..645cb841e4 100644
--- a/lib/std/child_process.zig
+++ b/lib/std/child_process.zig
@@ -221,7 +221,10 @@ pub const ChildProcess = struct {
             return term;
         }
 
-        try windows.TerminateProcess(self.id, exit_code);
+        windows.TerminateProcess(self.id, exit_code) catch |err| switch (err) {
+            error.PermissionDenied => return error.AlreadyTerminated,
+            else => return err,
+        };
         try self.waitUnwrappedWindows();
         return self.term.?;
     }
@@ -231,7 +234,10 @@ pub const ChildProcess = struct {
             self.cleanupStreams();
             return term;
         }
-        try os.kill(self.id, os.SIG.TERM);
+        os.kill(self.id, os.SIG.TERM) catch |err| switch (err) {
+            error.ProcessNotFound => return error.AlreadyTerminated,
+            else => return err,
+        };
         try self.waitUnwrapped();
         return self.term.?;
     }
diff --git a/lib/std/os.zig b/lib/std/os.zig
index d6d4f596a1..90e738d775 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -639,14 +639,14 @@ pub fn raise(sig: u8) RaiseError!void {
     @compileError("std.os.raise unimplemented for this target");
 }
 
-pub const KillError = error{PermissionDenied} || UnexpectedError;
+pub const KillError = error{ ProcessNotFound, PermissionDenied } || UnexpectedError;
 
 pub fn kill(pid: pid_t, sig: u8) KillError!void {
     switch (errno(system.kill(pid, sig))) {
         .SUCCESS => return,
         .INVAL => unreachable, // invalid signal
         .PERM => return error.PermissionDenied,
-        .SRCH => unreachable, // always a race condition
+        .SRCH => return error.ProcessNotFound,
         else => |err| return unexpectedErrno(err),
     }
 }
diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index d38a63ef39..05b754de8d 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -1593,11 +1593,12 @@ pub fn GetModuleFileNameW(hModule: ?HMODULE, buf_ptr: [*]u16, buf_len: DWORD) Ge
     return buf_ptr[0..rc :0];
 }
 
-pub const TerminateProcessError = error{Unexpected};
+pub const TerminateProcessError = error{ PermissionDenied, Unexpected };
 
 pub fn TerminateProcess(hProcess: HANDLE, uExitCode: UINT) TerminateProcessError!void {
     if (kernel32.TerminateProcess(hProcess, uExitCode) == 0) {
         switch (kernel32.GetLastError()) {
+            Win32Error.ACCESS_DENIED => return error.PermissionDenied,
             else => |err| return unexpectedError(err),
         }
     }

From fb9376bd0499e2124616da1aeed7fe4e8bdd4f52 Mon Sep 17 00:00:00 2001
From: Ben Crist <ben@magicmoremagic.com>
Date: Sun, 20 Nov 2022 17:41:33 -0600
Subject: [PATCH 2/2] Double check that child processes have really exited when

TerminateProcess reports ACCESS_DENIED
---
 lib/std/child_process.zig | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/std/child_process.zig b/lib/std/child_process.zig
index 645cb841e4..f8cb1be221 100644
--- a/lib/std/child_process.zig
+++ b/lib/std/child_process.zig
@@ -222,7 +222,15 @@ pub const ChildProcess = struct {
         }
 
         windows.TerminateProcess(self.id, exit_code) catch |err| switch (err) {
-            error.PermissionDenied => return error.AlreadyTerminated,
+            error.PermissionDenied => {
+                // Usually when TerminateProcess triggers a ACCESS_DENIED error, it
+                // indicates that the process has already exited, but there may be
+                // some rare edge cases where our process handle no longer has the
+                // PROCESS_TERMINATE access right, so let's do another check to make
+                // sure the process is really no longer running:
+                windows.WaitForSingleObjectEx(self.handle, 0, false) catch return err;
+                return error.AlreadyTerminated;
+            },
             else => return err,
         };
         try self.waitUnwrappedWindows();