cygwin.newlib-cygwin{,-nobin}: init at 3.6.4

pkgs/os-specific/cygwin/default.nix

···
       w32api = callPackage ./w32api { };
       w32api-headers = callPackage ./w32api { headersOnly = true; };
 
-      newlib-cygwin-headers = callPackage ./newlib-cygwin { };
+      newlib-cygwin = callPackage ./newlib-cygwin { };
+      # this is here to avoid symlinks being made to cygwin1.dll in /nix/store
+      newlib-cygwin-nobin = callPackage ./newlib-cygwin/nobin.nix { };
+      newlib-cygwin-headers = callPackage ./newlib-cygwin { headersOnly = true; };
     };
 }

pkgs/os-specific/cygwin/newlib-cygwin/default.nix

···
 {
   lib,
+  stdenv,
   stdenvNoCC,
+  stdenvNoLibc,
+  autoreconfHook,
+  bison,
   buildPackages,
-  fetchurl,
+  cocom-tool-set,
+  flex,
+  perl,
+  w32api,
   w32api-headers,
+
+  headersOnly ? false,
 }:
 
-stdenvNoCC.mkDerivation (finalAttrs: {
-  pname = "newlib-cygwin-headers";
-  version = "3.6.4";
+(if headersOnly then stdenvNoCC else stdenvNoLibc).mkDerivation (
+  finalAttrs:
+  {
+    pname = "newlib-cygwin${lib.optionalString headersOnly "-headers"}";
+    version = "3.6.4";
+
+    src = buildPackages.fetchgit {
+      url = "https://cygwin.com/git/newlib-cygwin.git";
+      rev = "cygwin-${finalAttrs.version}";
+      hash = "sha256-+WYKwqcDAc7286GzbgKKAxNJCOf3AeNnF8XEVPoor+g=";
+    };
+
+    outputs = [
+      "out"
+    ]
+    ++ lib.optionals (!headersOnly) [
+      "bin"
+      "dev"
+      "man"
+    ];
+
+    patches = [
+      # Newer versions of gcc don't like struct winsize being used before being
+      # declared. Backport of https://cygwin.com/cgit/newlib-cygwin/commit/?id=73600d68227e125af24b7de7c3fccbd4eb66ee03
+      ./fix-winsize.patch
+    ]
+    # After cygwin hosted builds are working, we should upstream this
+    ++ lib.optional (
+      !headersOnly && stdenvNoLibc.hostPlatform != stdenvNoLibc.buildPlatform
+    ) ./fix-cross.patch;
+
+    passthru.w32api = if headersOnly then w32api-headers else w32api;
+
+    meta = {
+      homepage = "https://cygwin.com/";
+      description = "A DLL which provides substantial POSIX API functionality on Windows.";
+      license = with lib.licenses; [
+        # newlib
+        gpl2
+        # winsup
+        gpl3
+      ];
+      platforms = lib.platforms.cygwin;
+      maintainers = [ lib.maintainers.corngood ];
+    };
+  }
+  // (
+    if headersOnly then
+      {
+        dontConfigure = true;
+        dontBuild = true;
+
+        installPhase = ''
+          mkdir -p $out/include/
+          cp -r newlib/libc/include/* $out/include/
+          cp -r winsup/cygwin/include/* $out/include/
+        '';
+      }
+    else
+      {
+        postPatch = ''
+          patchShebangs --build winsup/cygwin/scripts
+        '';
+
+        autoreconfFlags = [
+          "winsup"
+        ]
+        # Only reconfigure root when fix-cross.patch is applied. Otherwise the
+        # autoconf version check will fail.
+        ++ lib.optional (stdenvNoLibc.hostPlatform != stdenvNoLibc.buildPlatform) ".";
+
+        env =
+          let
+            libflag = "-Wl,-L${lib.getLib w32api}${w32api.libdir or "/lib/w32api"}";
+          in
+          {
+            CFLAGS_FOR_TARGET = toString [
+              libflag
+            ];
 
-  src = buildPackages.fetchgit {
-    url = "https://cygwin.com/git/newlib-cygwin.git";
-    rev = "cygwin-${finalAttrs.version}";
-    hash = "sha256-+WYKwqcDAc7286GzbgKKAxNJCOf3AeNnF8XEVPoor+g=";
-  };
+            CXXFLAGS_FOR_TARGET = toString [
+              "-Wno-error=register"
+              libflag
+            ];
+          };
 
-  patches = [
-    # newer versions of gcc don't like struct winsize being used before being
-    # declared.
-    ./fix-winsize.patch
-  ];
+        strictDeps = true;
 
-  dontConfigure = true;
-  dontBuild = true;
+        depsBuildBuild = [ buildPackages.stdenv.cc ];
 
-  installPhase = ''
-    mkdir -p $out/include/
-    cp -r newlib/libc/include/* $out/include/
-    cp -r winsup/cygwin/include/* $out/include/
-  '';
+        nativeBuildInputs = [
+          autoreconfHook
+          bison
+          cocom-tool-set
+          flex
+          perl
+        ];
 
-  passthru.w32api = w32api-headers;
+        buildInputs = [ w32api ];
 
-  meta = {
-    homepage = "https://cygwin.com/";
-    description = "A DLL which provides substantial POSIX API functionality on Windows.";
-    license = with lib.licenses; [
-      # newlib
-      gpl2
-      # winsup
-      gpl3
-    ];
-    platforms = lib.platforms.cygwin;
-    maintainers = [ lib.maintainers.corngood ];
-  };
-})
+        makeFlags = [
+          "tooldir=${placeholder "out"}"
+        ];
+
+        enableParallelBuilding = true;
+
+        # this is explicitly -j1 in cygwin.cygport
+        # without it the install order is non-deterministic
+        enableParallelInstalling = false;
+
+        hardeningDisable = [
+          # conflicts with internal definition of 'bzero'
+          "fortify"
+          "stackprotector"
+        ];
+
+        configurePlatforms = [
+          "build"
+          "target"
+        ];
+
+        configureFlags = [
+          "--disable-shared"
+          "--disable-doc"
+          "--enable-static"
+          "--disable-dumper"
+          "--with-cross-bootstrap"
+        ]
+        ++ lib.optional (stdenvNoLibc.hostPlatform != stdenvNoLibc.buildPlatform) [
+          "ac_cv_prog_CC=gcc"
+        ];
+      }
+  )
+)

pkgs/os-specific/cygwin/newlib-cygwin/fix-cross.patch

···
+Disable strict autoconf version check so we can autoreconf in nixpkgs.
+
+diff --git a/config/override.m4 b/config/override.m4
+index 8b954d3cb..60c4cfd12 100644
+--- a/config/override.m4
++++ b/config/override.m4
+@@ -44,7 +44,6 @@ AC_DEFUN([_GCC_AUTOCONF_VERSION_CHECK],
+   [m4_fatal([Please use exactly Autoconf ]_GCC_AUTOCONF_VERSION[ instead of ]m4_defn([m4_PACKAGE_VERSION])[.])])
+ ])
+ m4_define([AC_INIT], m4_defn([AC_INIT])[
+-_GCC_AUTOCONF_VERSION_CHECK
+ ])
+ 
+ 
+
+This is needed for target linking to find e.g. crt0.o.
+diff --git a/configure.ac b/configure.ac
+index 05ddf6987..f5bbd5c72 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -3166,7 +3166,7 @@ case " $target_configdirs " in
+   *" --with-newlib "*)
+    case "$target" in
+     *-cygwin*)
+-      FLAGS_FOR_TARGET=$FLAGS_FOR_TARGET' -L$$r/$(TARGET_SUBDIR)/winsup/cygwin -isystem $$s/winsup/cygwin/include'
++      FLAGS_FOR_TARGET=$FLAGS_FOR_TARGET' -B$$r/$(TARGET_SUBDIR)/winsup/cygwin -isystem $$s/winsup/cygwin/include'
+       ;;
+    esac
+ 
+
+Autoconf clears EXEEXT= in cross, which breaks installation of utils/cygserver.
+
+AC_CHECK_LIB is disabled in cross after AC_NO_EXECUTABLES.
+diff --git a/winsup/configure.ac b/winsup/configure.ac
+index e7ac814b1..14b56e130 100644
+--- a/winsup/configure.ac
++++ b/winsup/configure.ac
+@@ -40,6 +40,8 @@ AM_PROG_AS
+ AC_LANG(C)
+ AC_LANG(C++)
+ 
++EXEEXT=.exe
++
+ AC_ARG_WITH([cross-bootstrap],[AS_HELP_STRING([--with-cross-bootstrap],[do not build programs using the MinGW toolchain or check for MinGW libraries (useful for bootstrapping a cross-compiler)])],[],[with_cross_bootstrap=no])
+ 
+ AC_CYGWIN_INCLUDES
+@@ -135,8 +137,6 @@ AM_CONDITIONAL(BUILD_DUMPER, [test "x$build_dumper" = "xyes"])
+ # libbfd.a doesn't have a pkgconfig file, so we guess what it's dependencies
+ # are, based on what's present in the build environment
+ BFD_LIBS="-lintl -liconv -liberty -lz"
+-AC_CHECK_LIB([sframe], [sframe_decode], [BFD_LIBS="${BFD_LIBS} -lsframe"])
+-AC_CHECK_LIB([zstd], [ZSTD_isError], [BFD_LIBS="${BFD_LIBS} -lzstd"])
+ AC_SUBST([BFD_LIBS])
+ 
+ AC_CONFIG_FILES([

pkgs/os-specific/cygwin/newlib-cygwin/nobin.nix

···
+{
+  emptyDirectory,
+  newlib-cygwin,
+}:
+
+newlib-cygwin
+// {
+  bin = emptyDirectory;
+}

pkgs/os-specific/cygwin/newlib-cygwin/remove-definitions-that-conflict-with-mingw.patch

···
+From cc95494ed527e64fcd1ade7ed7ae44f9e0a6fa8a Mon Sep 17 00:00:00 2001
+From: David McFarland <[e-mail]>
+Date: Tue, 9 Sep 2025 15:04:45 -0300
+Subject: [PATCH] remove definitions that conflict with mingw
+
+---
+ winsup/cygwin/fhandler/socket_inet.cc  |  2 ++
+ winsup/cygwin/fhandler/socket_local.cc |  2 ++
+ winsup/cygwin/local_includes/ntdll.h   | 20 --------------------
+ winsup/cygwin/net.cc                   |  2 ++
+ 4 files changed, 6 insertions(+), 20 deletions(-)
+
+diff --git a/winsup/cygwin/fhandler/socket_inet.cc b/winsup/cygwin/fhandler/socket_inet.cc
+index 63cc498f1..03681c07b 100644
+--- a/winsup/cygwin/fhandler/socket_inet.cc
++++ b/winsup/cygwin/fhandler/socket_inet.cc
+@@ -20,7 +20,9 @@
+ #undef u_long
+ #define u_long __ms_u_long
+ #include <w32api/ws2tcpip.h>
++#define cmsghdr __ms_cmsghdr
+ #include <w32api/mswsock.h>
++#undef cmsghdr
+ #include <w32api/mstcpip.h>
+ #include <netinet/tcp.h>
+ #include <netinet/udp.h>
+diff --git a/winsup/cygwin/fhandler/socket_local.cc b/winsup/cygwin/fhandler/socket_local.cc
+index e4a88169b..b832d8a84 100644
+--- a/winsup/cygwin/fhandler/socket_local.cc
++++ b/winsup/cygwin/fhandler/socket_local.cc
+@@ -21,7 +21,9 @@
+ #define u_long __ms_u_long
+ #include "ntsecapi.h"
+ #include <w32api/ws2tcpip.h>
++#define cmsghdr __ms_cmsghdr
+ #include <w32api/mswsock.h>
++#undef cmsghdr
+ #include <unistd.h>
+ #include <asm/byteorder.h>
+ #include <sys/socket.h>
+diff --git a/winsup/cygwin/local_includes/ntdll.h b/winsup/cygwin/local_includes/ntdll.h
+index 4497fe53f..bf86a8293 100644
+--- a/winsup/cygwin/local_includes/ntdll.h
++++ b/winsup/cygwin/local_includes/ntdll.h
+@@ -489,26 +489,6 @@ typedef struct _FILE_DISPOSITION_INFORMATION_EX	// 64
+   ULONG Flags;
+ } FILE_DISPOSITION_INFORMATION_EX, *PFILE_DISPOSITION_INFORMATION_EX;
+ 
+-typedef struct _FILE_STAT_INFORMATION		// 68
+-{
+-  LARGE_INTEGER FileId;
+-  LARGE_INTEGER CreationTime;
+-  LARGE_INTEGER LastAccessTime;
+-  LARGE_INTEGER LastWriteTime;
+-  LARGE_INTEGER ChangeTime;
+-  LARGE_INTEGER AllocationSize;
+-  LARGE_INTEGER EndOfFile;
+-  ULONG FileAttributes;
+-  ULONG ReparseTag;
+-  ULONG NumberOfLinks;
+-  ACCESS_MASK EffectiveAccess;
+-} FILE_STAT_INFORMATION, *PFILE_STAT_INFORMATION;
+-
+-typedef struct _FILE_CASE_SENSITIVE_INFORMATION	// 71
+-{
+-  ULONG Flags;
+-} FILE_CASE_SENSITIVE_INFORMATION, *PFILE_CASE_SENSITIVE_INFORMATION;
+-
+ enum {
+   FILE_LINK_REPLACE_IF_EXISTS				= 0x01,
+   FILE_LINK_POSIX_SEMANTICS				= 0x02,
+diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
+index 737e494f8..6a1a0d079 100644
+--- a/winsup/cygwin/net.cc
++++ b/winsup/cygwin/net.cc
+@@ -18,7 +18,9 @@ details. */
+ #undef u_long
+ #define u_long __ms_u_long
+ #include <w32api/ws2tcpip.h>
++#define cmsghdr __ms_cmsghdr
+ #include <w32api/mswsock.h>
++#undef cmsghdr
+ #include <w32api/iphlpapi.h>
+ #define gethostname cygwin_gethostname
+ #include <unistd.h>
+-- 
+2.50.1
+

pkgs/os-specific/windows/default.nix

···
   newScope,
   overrideCC,
   stdenvNoLibc,
+  emptyDirectory,
 }:
 
 lib.makeScope newScope (

pkgs/top-level/all-packages.nix

···
         isl = if !stdenv.hostPlatform.isDarwin then isl_0_20 else null;
 
         withoutTargetLibc = true;
-        langCC = false;
+        langCC = stdenv.targetPlatform.isCygwin; # can't compile libcygwin1.a without C++
         libcCross = libc1;
         targetPackages.stdenv.cc.bintools = binutilsNoLibc;
         enableShared =
···
       if stdenv.hostPlatform.isMinGW then windows.mingw_w64 else windows.sdk
     else if libc == "ucrt" then
       if stdenv.hostPlatform.isMinGW then windows.mingw_w64 else windows.sdk
+    else if libc == "cygwin" then
+      cygwin.newlib-cygwin-nobin
     else if libc == "libSystem" then
       if stdenv.hostPlatform.useiOSPrebuilt then darwin.iosSdkPkgs.libraries else darwin.libSystem
     else if libc == "fblibc" then