From 208ed3c538e9ea2f4027b6976c4f689ba28035fd Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Wed, 17 Dec 2025 12:25:25 -0500
Subject: [PATCH] Fix `select` / `fdset` usage on Windows

These functions use `SOCKET` not `int`, despite them being unix
functions.
---
 src/libutil/serialise.cc | 10 +++++-----
 src/nix/unix/daemon.cc   | 11 ++++++-----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 9791b4fed..e71ec66d2 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -1,6 +1,7 @@
 #include "nix/util/serialise.hh"
 #include "nix/util/compression.hh"
 #include "nix/util/signals.hh"
+#include "nix/util/socket.hh"
 #include "nix/util/util.hh"
 
 #include <cstring>
@@ -11,7 +12,6 @@
 
 #ifdef _WIN32
 #  include <fileapi.h>
-#  include <winsock2.h>
 #  include "nix/util/windows-error.hh"
 #else
 #  include <poll.h>
@@ -184,20 +184,20 @@ bool FdSource::hasData()
     while (true) {
         fd_set fds;
         FD_ZERO(&fds);
-        int fd_ = fromDescriptorReadOnly(fd);
-        FD_SET(fd_, &fds);
+        Socket sock = toSocket(fd);
+        FD_SET(sock, &fds);
 
         struct timeval timeout;
         timeout.tv_sec = 0;
         timeout.tv_usec = 0;
 
-        auto n = select(fd_ + 1, &fds, nullptr, nullptr, &timeout);
+        auto n = select(sock + 1, &fds, nullptr, nullptr, &timeout);
         if (n < 0) {
             if (errno == EINTR)
                 continue;
             throw SysError("polling file descriptor");
         }
-        return FD_ISSET(fd, &fds);
+        return FD_ISSET(sock, &fds);
     }
 }
 
diff --git a/src/nix/unix/daemon.cc b/src/nix/unix/daemon.cc
index 406258ff8..661488c56 100644
--- a/src/nix/unix/daemon.cc
+++ b/src/nix/unix/daemon.cc
@@ -437,22 +437,23 @@ static void forwardStdioConnection(RemoteStore & store)
     int from = conn->from.fd;
     int to = conn->to.fd;
 
-    auto nfds = std::max(from, STDIN_FILENO) + 1;
+    Socket fromSock = toSocket(from), stdinSock = toSocket(getStandardInput());
+    auto nfds = std::max(fromSock, stdinSock) + 1;
     while (true) {
         fd_set fds;
         FD_ZERO(&fds);
-        FD_SET(from, &fds);
-        FD_SET(STDIN_FILENO, &fds);
+        FD_SET(fromSock, &fds);
+        FD_SET(stdinSock, &fds);
         if (select(nfds, &fds, nullptr, nullptr, nullptr) == -1)
             throw SysError("waiting for data from client or server");
-        if (FD_ISSET(from, &fds)) {
+        if (FD_ISSET(fromSock, &fds)) {
             auto res = splice(from, nullptr, STDOUT_FILENO, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
             if (res == -1)
                 throw SysError("splicing data from daemon socket to stdout");
             else if (res == 0)
                 throw EndOfFile("unexpected EOF from daemon socket");
         }
-        if (FD_ISSET(STDIN_FILENO, &fds)) {
+        if (FD_ISSET(stdinSock, &fds)) {
             auto res = splice(STDIN_FILENO, nullptr, to, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
             if (res == -1)
                 throw SysError("splicing data from stdin to daemon socket");