From c76fc02aed813084af8849570721a088d3d8df8b Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Sun, 13 Sep 2026 01:53:18 +0200
Subject: [PATCH] Implement IO_gethostname on Windows

There gethostname is part of Winsock, which configure does not find, so
the function was absent. Packages probing for it with IsBoundGlobal,
such as cvec and homalgtocas, then called the stub bound for absent
functions and failed. GetComputerNameA needs no network setup.

Assisted-by: Claude Code (Opus 5)
---
 src/io.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/io.c b/src/io.c
index 6dcf37c..5819eea 100644
--- a/src/io.c
+++ b/src/io.c
@@ -40,6 +40,8 @@
 #include <errno.h>
 #ifdef _WIN32
 #include <direct.h>    // for _mkdir
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>    // for GetComputerNameA
 #endif
 
 // Tracking child processes needs SIGCHLD and waitpid, which native Windows
@@ -1968,6 +1970,17 @@ static Obj FuncIO_gethostname(Obj self)
     }
     return MakeString(name);
 }
+#elif defined(_WIN32)
+// gethostname is part of Winsock; the computer name needs no network setup
+static Obj FuncIO_gethostname(Obj self)
+{
+    char  name[MAX_COMPUTERNAME_LENGTH + 1];
+    DWORD len = sizeof(name);
+    if (!GetComputerNameA(name, &len)) {
+        return Fail;
+    }
+    return MakeString(name);
+}
 #endif
 
 static Obj FuncIO_getenv(Obj self, Obj name)
@@ -2265,7 +2278,7 @@ static StructGVarFunc GVarFuncs[] = {
     GVAR_FUNC(IO_getsockname, 1, "fd"),
 #endif
 
-#ifdef HAVE_GETHOSTNAME
+#if defined(HAVE_GETHOSTNAME) || defined(_WIN32)
     GVAR_FUNC(IO_gethostname, 0, ""),
 #endif