From af3ab2e2e3c63d6412d70d1f2c75c10c54253b95 Mon Sep 17 00:00:00 2001
From: Nikias Bassen
Date: Wed, 4 Jun 2025 11:52:59 +0200
Subject: configure: [Windows] Add --with-winver option to specify minimum
 Windows version

This effectively defines WINVER and _WIN32_WINNT to the specified value
which will compile the code with that minimum supported Windows version
instead of the compiler/SDK default.
The passed value is expected to be in hex (like 0x0600) or decimal, so
passing --with-winver=0x0600 is a valid accepted input. See
https://learn.microsoft.com/cpp/porting/modifying-winver-and-win32-winnt
for the values of different Windows versions.
---
 configure.ac | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 0f0a755..5471ad3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -71,7 +71,24 @@ case ${host_os} in
   *mingw32*|*cygwin*)
     AC_MSG_RESULT([${host_os}])
     win32=true
-    AC_DEFINE(WINVER, 0x0501, [minimum Windows version])
+    AC_ARG_WITH([winver],
+      [AS_HELP_STRING([--with-winver], [Set the minimum windows version])],
+      [
+        AS_CASE([${withval}],
+          [0x[[0-9A-Fa-f]]|0x[[0-9A-Fa-f]]*[[0-9A-Fa-f]]], [VAL=${withval}],
+          ['' | *[[!0123456789]]*], [VAL=""],
+          [[[!0]]*], [VAL=${withval}],
+          [VAL=""]
+        )
+        AS_IF([test "x$VAL" != "x"], [
+          AC_DEFINE_UNQUOTED(WINVER, ${VAL}, [minimum Windows version])
+          AC_DEFINE_UNQUOTED(_WIN32_WINNT, ${VAL}, [minimum Windows version])
+        ], [
+          AC_MSG_ERROR([--with-winver expects a hexadecimal value like 0x0600, or a decimal, and must not be 0])
+        ])
+      ],
+      []
+    )
     ;;
   darwin*)
     AC_MSG_RESULT([${host_os}])
-- 
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